“I’m doing Intermittent Fasting. What can I eat and drink during my fast?”
“Can I eat/drink [insert food/drink] during my fast?”
“Does x number of calories break a fast?”
“Will drinking BCAAs break my fast?”
“Do artificial sweeteners break a fast?”
All these are commonly asked questions by people who engage in different types of intermittent fasting, whether that’s alternate day fasting, the Lean Gains protocol, 5:2, and so on. And all are perfectly valid questions to ask, mind you.
Unfortunately, however, the answers to the questions above are a little more complicated and less straightforward than you may think. Don’t you worry, though, because, by the end of this article, your questions will be answered!
By the way, big shout out to the IF Facebook group, if that’s what brought you here!
Key takeaway points
If you’re in a rush and don’t have time to go through the entire article, here are some of the key takeaways:
- Intermittent fasting is, essentially, an eating pattern which involves alternating periods of little or no energy intake (i.e. caloric restriction) with intervening periods of normal food intake, on a recurring basis.
- There are three types of intermittent fasting: alternate day fasting (ADF), whole day fasting (WDF), and time-restricted feeding (TRF).
- Fasting can mean one of two things: 1. completely abstaining from food, and 2. eating sparingly or abstaining from some foods.
- Different people fast for different reasons, including to lose weight, to improve their health, to test their mental toughness, and for religious reasons.
- Fat loss is the result of a caloric deficit. According to research, when calories and protein are controlled for, fasting per se doesn’t seem to increase fat or weight loss. This means that you don’t, technically, have to fast to maximize fat loss, which makes the question of what you can eat or drink during a fast when your goal is fat loss kind of irrelevant to begin with.
- Most research on intermittent fasting for improved health and longevity suffers from serious methodological limitations. What we currently know from research is that there MAY be health and longevity benefits to fasting, but that there is, currently, no strong evidence from research in humans in the absence of caloric restriction to support this. This also makes the question of what you can eat or drink during a fast when your goal is better health and longevity kind of irrelevant to begin with.
- Despite the above, there are still good reasons why you should try intermittent fasting, such as better caloric control, improved hunger awareness, the ability to have bigger and more satisfying meals, more social flexibility, potentially improved sustainability and better dietary adherence, and improved productivity during the fasted state.
- A good general rule is that ingesting calories breaks a fast. While a splash of milk or cream in your coffee will, technically, break your fast, it won’t interfere with your results as long as those calories are accounted for.
- BCAA products (all of them, despite what the nutritional label on the product says) contain calories and will break your fast.
Okay, so let’s get right into it!
What is Intermittent Fasting?
Before we talk about what you can eat during a fast, let’s first briefly explain what intermittent fasting is.
Simply put, intermittent fasting is, essentially, an eating pattern which involves alternating periods of little or no energy intake (i.e. caloric restriction) with intervening periods of normal food intake, on a recurring basis.
There are, generally, three different types of intermittent fasting according to research:
- Alternate day fasting (ADF), which involves a 24-hour fasting or very low calorie period, alternated with a 24-hour ad libitum eating period.
- Whole day fasting (WDF), which usually involves 1-2 days of fasting or very low calorie periods per week, with the remaining days of the week eating at maintenance.
- Time-restricted feeding (TRF), which involves a fasting period of 16–20 hours and a feeding period of 4–8 hours daily, and includes the Leangains protocol by Martin Berkhan. This is probably the most popular of the three types of intermittent fasting.
An example of a TRF protocol is as follows: you may set your fasting period to be from 10 pm on one day until 4 pm on the following day. This gives you 18 hours of fasting and an eating window of 6 hours (from 4 pm until 10 pm every day). This is known as the 18:6 protocol among those practicing intermittent fasting.
Other protocols are 14:10 (fasting for 14 hours), 16:8 (fasting for 16 hours), 20:4 (fasting for 20 hours) and so on.
Which leads us to our next question.
What exactly is fasting?
According to the Merriam-Webster Dictionary, to fast can mean one of two things:
- to abstain from food,
and - to eat sparingly or abstain from some foods.
As you can understand, since fasting can, technically, mean both completely abstaining from food AND eating a little/not eating some foods, we’re in a bit of a pickle.
Remember when, at the start of this article, we said that things are not as straightforward as you may think? Well, this is partly why.
Hold your horses, though, because this is going to get a little more complicated.
Why would someone fast in the first place?
The motives behind why people fast are also something important to consider when trying to decide what you can eat and drink during a fast, as this can affect what you are technically “allowed” to have.
So why do people fast?
Well, different people fast for different reasons, the most common ones being:
- to lose fat and weight,
- to improve their health and increase longevity,
- for religious reasons, and
- to test their “mental toughness”.
What you can eat and drink during a fast
Okay, so let’s consider the reasons we listed above for why people fast and try to figure what you can eat and drink during your fast for each of these reasons.
1. Fasting for fat loss and weight loss
To answer the question of what you can eat and drink during your fast when your primary goal is weight loss, we must first consider how fasting helps with weight loss in the first place.
In short, the general line of thinking goes like this: When doing IF, the fasting periods result in lower insulin levels and higher human growth (HGH) hormone levels which, in turn, cause increased fat burning and, consequently, weight loss.
Is this, however, an accurate description of what happens? Well, according to scientific research, it’s true that, when we fast, our insulin levels drop and our HGH levels increase. What does research show, however, with regards to the end result, i.e. actual fat and weight loss? Do fasting-related lower insulin levels and higher growth hormone levels really result in more fat loss?
With regards to insulin, we can look at research comparing low carb/ketogenic diets with energy- and protein-matched higher carb diets for the answer, since these were designed to examine whether insulin per se plays a key role in fat loss. In short, a number of well-controlled studies such as this metabolic ward study, this metabolic ward study and this meta analysis provide good evidence to support the idea that low carbohydrate diets and ketogenic diets don’t seem to work better for fat loss when caloric and protein intakes are controlled for.
With regards to human growth hormone, research on intermittent fasting can shed some light. In short, studies that have compared intermittent fasting approaches to continuous energy restriction while controlling for caloric and protein intakes, such as this one, this one, and this one, have shown that, overall, the two diet types result in identical outcomes in terms of body weight and body fat reduction.
Why is that, however? If lower insulin levels and higher growth hormone levels aren’t the reasons why intermittent fasting works for fat loss, then how does intermittent fasting work?
Well, as we’ve talked about before, fat loss is the result of a sustained imbalance between energy intake and output. Simply put, to lose fat we have to take in fewer calories than we expend consistently over time. This is indisputable, by the way, and supported by every well-controlled study in the history of ever.
And this is, essentially, how intermittent fasting (and every other diet approach) works for weight loss – by helping you eat less, overall.
So where does this leave us with regards to what you can eat and drink during your fast?
Well, in reality, if your only goal is weight (and fat) loss, you can technically eat and drink anything you want at any time of the day, provided that you are maintaining a caloric deficit.
Eating throughout the day, of course, means that you won’t be doing intermittent fasting. And, yes, this means that you don’t HAVE TO do intermittent fasting if it isn’t practical for you and if it doesn’t help you adhere to your diet.
Remember, intermittent fasting is merely a meal timing tool which is supposed to help you control your caloric intake.
Take home point:
If your primary goal is to lose weight, the answer to the question “can I eat/drink [whatever] during my fast?” is “you can, technically, do whatever you want, as long as you are maintaining a caloric deficit consistently over time.
However, if you are consuming foods/drinks with calories, you wouldn’t be fasting. But it doesn’t really matter, since it’s not the fasting per se that causes fat and weight loss, but, instead, the fact that intermittent fasting helps most people eat less overall.”
2. Fasting for better health
Next on our list is fasting for better health.
Okay, so you don’t, technically, have to fast to lose weight, but fasting can improve health and increase longevity, right? After all, scientific research has shown that fasting results in a number of health benefits, including:
- improved insulin sensitivity,
- lower levels of inflammation,
- cancer-prevention properties,
- better brain health, and
- increased lifespan.
Well, unfortunately, if you take a closer look at the studies most health blogs usually cite, you will realize that the available scientific research suffers from a number of serious methodological problems, including that it is mostly limited to:
- animal studies – a number of systematic reviews such as this one, this one, this one, this one, and this one, have demonstrated poor clinical utility of animal experimentation,
- in vitro studies – i.e. with microorganisms or cells outside their normal biological context, usually in a test tube or petri dish,
- mechanistic studies – i.e. studies discussing how one thing might affect another, but not actually trying it and seeing it happen in real life, and
- studies that don’t control for caloric intake – caloric restriction and weight loss have been shown to have a multitude of health and anti-aging benefits in countless of studies. Since intermittent fasting tends to result in caloric restriction, it’s difficult to attribute the health benefits found to fasting per se, when there is the confounding variable of energy balance.
In short, what we currently know from research is that there MAY be health and longevity benefits to fasting without caloric restriction, but that there is, currently, no strong evidence from research in humans to support this.
“But this article/study says that fasting has health benefits”.
Okay, before you rush to any conclusions, investigate further!
Don’t just accept what the news website reports or what the abstract of a study says as facts just because they tell you what you want to hear. More often than not, claims are, at best, exaggerated by news websites, while study abstracts usually don’t tell the full story.
Remember to check the four points above, i.e. that the study referenced:
- is not in animals,
- is not in vitro,
- is not mechanistic in nature, and
- that it controls for energy intake.
So where do the above us with regards to what you can eat and drink during your fast when fasting for increased health and longevity?
Well, simply put, focusing on just fasting to improve your health is missing the forest for the trees, since it doesn’t look like it’s fasting per se that has health benefits but, instead, the overall decrease in energy intake as well as the accompanied fat loss.
Take home point:
Fasting MAY have some health benefits, but there is no strong scientific evidence to support this yet, so don’t stress about x food/drink breaking your fast or not. Remember that there are a few things that you can do that are much more important than fasting.
If you want to improve your health, make sure that, above all, you are:
- maintaining a healthy weight,
- eating a diet that is based on plants, lean proteins and healthy fats,
- exercising regularly,
- not smoking,
- not drinking excessively,
- not stressing, and
- maintaining healthy social relationships.
3 & 4. Fasting for religious reasons and to test mental toughness
Fasting for these reasons is more of a personal matter and beyond the scope of this article. If your religion says that you have to completely abstain from foods for so many hours or from some foods for so many days, it’s entirely up to you to decide whether you want to do it or not.
The same applies to fasting for mental toughness. If you want to test your limits and see how long you can fast for, it’s your decision to make.
Just bear in mind that prolonged fasts can be dangerous and should, preferably, be done under the close supervision of a licenced health professional.
Why do Intermittent Fasting then?
So if fasting per se isn’t what results in weight loss and health improvements, why then do intermittent fasting in the first place?
Well, although fasting doesn’t seem to have any “magical” properties in and of itself, there are a number of good reasons why you should consider doing intermittent fasting! This is, after all, why we often use this approach with many of our online fitness coaching clients!
So here are a few reasons why you should consider doing intermittent fasting (credit to the Pinned Post of the official Intermittent Fasting Facebook group for these):
1. More structured eating
How often have you found yourself mindlessly snacking between meals? A couple of cookies with your coffee, a small piece of cake that Suzy brought for her birthday at work, a few nuts and dried fruits before dinner, some popcorn with a movie at night. When you think about it, little snacks here and there can add up to quite a few calories. Well, the more structured eating that is a result of intermittent fasting can eliminate this problem and can help people better control their diet.
2. Bigger, more satisfying meals
Eating every 2-3 hours sucks. For one, it’s impractical and makes you think of food all day. It also means that you never really get to eat big meals, especially if you are a smaller, physically inactive person. On the other hand, more infrequent meals that are larger in volume and provide more calories are usually much more satisfying and may help you feel fuller for longer.
3. Sustainability and adherence
Diets that control calories over the long term lead to weight loss success. Eating larger meals less frequently usually tends to increase adherence to the diet over the long haul.
4. Social Flexibility
Humans are social creatures and most of us nowadays tend to build social occasions around food, with these occasion usually taking place in the evening. By fasting throughout the day, you enable yourself the freedom to eat the foods served at social gatherings while still staying within your calorie goals for the day. Remember, a diet that doesn’t promote social flexibility is really hard to maintain.
5. Improved hunger awareness
When eating throughout the day, it’s not uncommon to eat for reasons other than hunger. For example, many people tend to eat because of boredom, sadness, stress, or happiness. Also, even the smell of food can make us think we’re hungry and cause us to want to eat (walk by a bakery and listen to your stomach growl!). Well, fasting can help improve hunger awareness, making you realize what real physical hunger feels like and how to differentiate it to “hunger” arising from environmental or psychological factors.
6. More productivity
Since eating takes up time, having fewer meals can often help people get more stuff done during the day, thereby, increasing productivity.
Let’s recap
Okay, so with all the above in mind, let’s recap and try to answer all the questions asked at the beginning of the article.
“I’m doing Intermittent Fasting. What can I eat and drink during my fast?”
If you are doing intermittent fasting to lose fat and weight, you can technically eat and drink whatever you want at any time of the day, provided that you are maintaining a sustained caloric deficit over the long term. This means that IF may help you lose fat if it makes it easier for you to reduce overall energy intake, but that you don’t HAVE TO do IF to lose fat and weight.
If you are doing IF for the purported health and longevity benefits of fasting, you may be disappointed to hear that we don’t know for certain if these exist in humans yet. There are a few things you can do that will have a much larger impact on your health anyway, such as maintaining a healthy body weight, eating a diet that is based primarily on plants, lean meats, fish and healthy fats, exercising, not smoking, not drinking excessively, not stressing too much, and maintaining healthy social relationships, so it’s a better idea to focus your energy on these instead.
“Can I eat/drink [insert food/drink] during my fast?”
Does eating/drinking that food or drink make it easier for you to improve your overall diet in terms of better food quality and lower calorie intake? If yes, go for it. If no, don’t.
“Does x number of calories break a fast?”
There’s no set number of calories that breaks a fast. The person who first came up with this probably did so to allow people to have a splash of milk or cream in their coffee without stressing about it, but to also keep them from going overboard with the calories and not managing to create a caloric deficit by the end of the day.
“Will drinking BCAAs break my fast?”
Despite what most people think (and what the nutritional info label on your BCAA product says) ALL BCAA products contain calories. Leucine and isoleucine contain 4.65 calories per gram, while valine contains 4.64 calories per gram. With the typical 2:1:1 ratio of most BCAA products, this means that 10g of BCAAs contain around 46.5 calories.
So yes, BCAAs break your fast. However, it doesn’t really matter if they do or don’t in the first place.
“Do artificial sweeteners break a fast?”
Artifical sweeteners contain, practically, no calories, so they don’t break a fast. For example, a typical can of aspartame-sweetened soda contains less than half a calorie.
Also, contrary to what many people think, artificial sweeteners don’t cause insulin secretion (diabetics would be dropping dead everywhere if this was the case) or somehow make you gain fat or weight (the association between artificial sweetener consumption and obesity in research doesn’t imply causation – it most likely means that people who are overweight tend to switch to diet soda in an effort to lose weight).
What next?
If you enjoyed this article and found it informative, you’ll probably also like these ones as well:
- Do BCAAs Have Calories? Settling the Debate Once and for All
- The Evidence for Caloric Restriction: A Response to Dr. Fung’s CrAP
- CICO: The Evidence-Based Truth You Need to Know
https://m.facebook.com/story.php?story_fbid=482048782180877&id=100011272786132
Thanks for your comment, Tom.
Unfortunately, although this article is being shared all the time, no one seems to have bothered to look up the actual research that it is based on. Here it is: http://www.cell.com/cell-stem-cell/fulltext/S1934-5909(14)00151-9
As you will notice, the studies were done on mice and, unfortunately, nutrition and supplementation research almost never translates well from mice to humans.
Here’s a quote from our article:
“You see, although it has been claimed multiple times that fasting can improve health and increase longevity, the research showing these benefits is limited to:
– animal studies (which 99.9% of the time don’t translate to humans in drug/nutrition/supplementation research)
– in vitro studies (i.e. in a test tube)
– mechanistic studies (i.e. studies discussing how one thing might affect another, but not actually trying it and seeing it happen in real life)
– studies that don’t control for caloric intake (caloric restriction and weight loss have been shown to have a multitude of health benefits in countless of studies)”
Anyone who watched interviews on Dr Longo (or read his book on the fasting mimicking diet) the medical scientist who conducted early clinical studies on intermittent fasting using mice and humans he explains how the body and cells reacts to fasting and refeeding and the benefits will know that the concept for their studies was not based on the dictionary’s definition of fasting but rather on cellular changes that occurs when the body is in the fasting stage but more importantly the refeeding phase that generates weight loss and a multitude of health benefits.
Hi Jennifer and thanks for your comment.
It’s funny that you are mentioning Valter, as I have read pretty much all of his research on fasting 🙂
What I would encourage you to do is to read his actual research rather than just listen to podcasts and interviews, as the former goes through a peer-review process which ensures that he is less likely to make exaggerations that can easily be made outside of the peer-review process.
Here’s, for example, a 2017 review of intermittent fasting on health and disease from Valter that you can read: https://www.freedomsphoenix.com/Media/Media-Files/1-s2.0-S1568163716302513-Longo-IF.pdf
If you focus on the research that is in humans, you’ll notice that the effects of IF can’t really be separated from those of caloric restriction. As we’ve mentioned in the article above, “caloric restriction and weight loss have been shown to have a multitude of health and anti-aging benefits in countless of studies. Since intermittent fasting tends to result in caloric restriction, it’s difficult to attribute the health benefits found to fasting per se, when there is the confounding variable of energy balance.”
Here are a few quotes from the study that you may find interesting:
On insulin sensitivity: “Thus, IF has been reported to have variable effects on peripheral and hepatic insulin sensitivity which may be different in obese and normal weight subjects and may be gender-specific. Further studies are required using more robust measures of insulin sensitivity e.g. insulin clamp or other techniques.”
On cardiovascular disease: “However, there have been few studies that have evaluated the relative effects of IF and Continuous Energy Restriction on cardiovascular risk markers. The randomized comparisons of IF and Continuous Energy Restriction have reported equivalent reductions in blood pressure (Hill et al., 1989a; Harvie et al., 2011, 2013a) and triglycerides (Hill et al., 1989a), (Ash et al., 2003). (Harvie et al., 2011, 2013a), and increased LDL particle size (Varady et al., 2011).”
On cancer risk: “Thus, although limited,the available biomarker data suggest that IF leads to comparable changes in most cancer risk biomarkers to Continuous Energy Restriction, with the possible exceptions of insulin resistance and adiponectin which require further study using robust methodologies. ”
Looking forward to your thoughts!
Hello, what about fasting to induce autophagy?
https://medium.com/the-mission/the-sweet-spot-for-intermittent-fasting-9aae12a2158c
Thanks for your comment, Corey.
Caloric restriction itself induces autophagy. In fact, it may be that the reason fasting induces autophagy is because it usually results in a decrease in energy intake.
Here is some relevant research:
http://onlinelibrary.wiley.com/doi/10.1196/annals.1396.020/full
http://onlinelibrary.wiley.com/doi/10.1002/ajhb.22243/full
http://www.ingentaconnect.com/content/ben/cas/2008/00000001/00000001/art00002
Animal studies 99.9% don’t translate to humans in drug/nutrition/supplementation research? That’s an extremely high failure rate. I’m assuming this figure was pulled from a peer-reviewed journal, since it’s such an exact value? Would you mind posting a link to the source in which you pulled this figure from? Much appreciated!
Hello Matt and thank you for your comment.
That was, indeed, an exaggerated statement on our part, and it has been edited to be more accurate.
Thanks again!
Hi,
Thanks for the article.
I am curious if you have had a chance to look at some of the studies that claim fasting can:
– Decrease insulin resistance
– Increase HGH levels
– Increase testosterone levels
– Increase sirtuin production
Are they founded? Has calorie control been known to trigger these same effects?
Also, you address fat-loss but are vague to what that entails and if that keeps in mind body composition. Are there not studies that show body composition can be improved by ketosis? And that ketosis triggers muscle sparing that contributes to body composition during weight loss?
Would love to hear what you/the-body-of-science think!
-Teddy
Hi Teddy and thanks for your comment!
OK, so perhaps the biggest “problem” with research on IF is that it often doesn’t control for caloric intake – and people aren’t taking this into account when looking at research.
Think about this – We know that caloric restriction (and the associated weight loss):
– results in improvements in insulin sensitivity (in overweight people)
– results in improvements in testosterone levels (in overweight people)
– results in increased sirtuin production and longevity
So if a group of subjects are doing IF while also eating a hypocaloric diet, then can we attribute the beneficial outcomes to IF, when we know for a fact that caloric restriction also has the same beneficial effects? 🙂 In my opinion, no.
You can check out this narrative review on the topic, for example, (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371748/), which looked exclusively at studies that matched caloric intake between groups (TRF and CER) and which concluded that the available research hasn’t yet shown any definitive benefits of IF with regards to weight loss, insulin sensitivity, RMR, etc.
You’ll notice that the review above also looks at lean body mass retention, and essentially concludes that IF doesn’t seem to have any LBM sparing benefits when calories, protein and physical activity are controlled.
Regarding HGH, I think most people are misunderstanding what exactly is happening and why. In simple terms, HGH increases during fasting simply as a normal physiological response to help substrate mobilization. It’s the same as, say, insulin increasing when we eat in order to increase the uptake of glycogen and amino acids in muscles, increase the synthesis and absorption of lipids in fat tissue, etc. There’s nothing “good” or “bad” about these. They are just normal physiological responses that happen for a reason and, outside the context of the overall surpluses and deficits that happen all the time, don’t really mean much.
Regarding ketosis, again, when calories and protein are controlled for, there’s little reason to believe that it should result in improved body composition relative to a higher carb diet. To learn more about this, I would urge you to read the “Carbohydrates” part of this paper: https://jissn.biomedcentral.com/articles/10.1186/1550-2783-11-20.
Would be interested in hearing your thoughts!
P.S. I’ve written an article for another big fitness website discussing much of what you’re asking here, which should be published sometime this month! We’ll share it through our social media accounts when it does, so keep an eye out for it! 🙂
Thank you for such a quick and thorough response, I’ve learned a lot ! Looking forward to your next article.
Happy I could help!
The important thing about a ketogenic diet is not that it somehow magically increases metabolism, (it obviously doesn’t,) but rather that it puts your metabolism in a different “mode” (burning fat when you run out of sugar and deplete glycogen stores.)
Yes, a calorie is a calorie. BUT, prolonged low blood sugar states (induced by reducing carb intake via keto diet) COMBINED with intermittent fasting will burn more fat than intermittent fasting combined with a typical diet including carbs. In the latter, during which the metabolism will be in it’s default glucose-burning mode, much of the “fasting” period will be spent burning through glycogen stores in the muscles. Only after the glycogen stores are depleted and the subject maintains fasting will actual fat loss occur. The studies provided only looked at energy expenditure, which misses this very important point entirely.
Again, this is not a disagreement. A calorie deficit is the only way to burn fat. It’s just that a ketogenic diet will set your metabolism from it’s default glucose-using state to the fat-using state (ketosis) BEFORE fasting begins, so that when it’s time to fast you spend more hours physically burning fat than having to burn through sugar first.
Hello Marisa and thanks for your comment.
It’s true that ketogenic diets will cause the body to burn more fat. What you’re not considering, however, is that most of the extra fat burned is dietary fat and not body fat, since ketogenic diets are inherently high in fat.
This is, of course, why metabolic ward research comparing ketogenic to non-ketogenic diets with matched calories and protein has consistently failed to detect any differences in fat loss between groups.
I suggest you give this article a read: https://www.myoleanfitness.com/ketogenic-diet-40-years-ago/
I have been doing Keto with IF and only things thats worked. For me. Tried lots fad diets, SW & WW. Loads gym etc. As soon as I stopped the carbs, sugars, ate fat ( which always a ovoided). Am 52 , gained subborn body fat, and was about to accept it was my age, hormones, etc… Had a stone and half to get off, which as I say was about to give up and accept my extra midriff
What I will say YES I do have to eat around a set defacit, which is only way eating as a fat burner that my body will once its has used the dietry fat, has burnt off body fat!! It did do that, it fell,off. Woo hoo.
I worked out my natural BMR. Deducted 500 cals. So once my body burns the dietry fat to that amount of fuel, of course it will go,burn the body fat for its remaining energy it needs to meet my BMR needs.
Thats what I do.
I also IF 16:8 every day, and it has maintained for first time ever!!
Im keen to keep insulin levels ticking very low ( have type 2 diebetes in family) and I do think I could poss had been early insulin resistance, as carbs and sugars made me feel ruff.
So basically keto, ‘fat burner’ does burn body fat, providing you stick to it, eat little carbs/sugar and moderate protein, count macros accoridng to calorie intake BMR with reduction of 15-20% so you are in defacit.
Only those who,consume too much fat, and do,not moderate their macros, as yes fat is very high in cals, it wont burn anything other than dietry fat.
Physically I feel,better, sleep,better, more energetic, aches and pains in joints eased, slimmer, skin better, and no,hunger pangs all time. I find IF easier on Keto, and even eat 2 meals nutrient dense a day only now.
Our bodies in my olinion from my experience react mich better to natural,healthy fats, I eat plenty of low carb veg & salad. Mineral and vit suplliments to help.
Keto & IF very powerful together for weight loss in controlled macro to calories needed for sure!!
As for studies etc, I am going from personal experience and my own research. A dieter all my life, always gained weight so easy, yo yo dieting, for once at last found something that actually works and keeps it off.
I know people whos diebetes and other health issues have gone, from ditching carbs and sugars, and eating fats. Amazing!!
Hey Sam,
It’s great that an approach combining IF and keto has helped you control your energy intake and make healthier food choices! Keep it up! 🙂
Myolean Fitness: “Yes, a Keto diet burns more fat, but it’s dietary fat that you’re eating a lot of, not body fat, which is the fat that makes you look fat.”
Sam: “I’m on Keto and IF and I’m losing body fat like crazy.”
Myolean Fitness: “Oh.”
Perhaps that “Oh” should be changed to “D’oh!”
It truly is shocking how a ketogenic diet combined with IF can help you eat less and, consequently, lose fat!
Doh!
Based on what you say, there is no benefit in IF.
It personally helped me deal with Myocarditis, and regulated my diet and Cravings. I never felt better. So there is a massive change in my life overall, not related to weight or fat lose as i never had this problem.
Seems to me like you are gathering all the article that supports your claims, and there milions of more articles that says different. Ive been following dr. Eric Berg, and what you are claiming completely contradicts what he has been saying for years.
So call me a bit naive, as i am a part of the general polulation, isnt it better to try things and decide for yourself what is benefitial and what is not? I only ask this as ifind your article very discouraging towards IF.
There is a benefit in regards to insulin and sugar level stabilisation – i am a living example, and i am not an animal either.
Hello Lucad and thank you for your comment,
You wrote: “Based on what you say, there is no benefit in IF.”
Well, not exactly. What the article says is, and I quote: “In short, what we currently know from human research is that there MAY be health and longevity benefits to fasting without caloric restriction, but that there is, currently, no strong evidence to support this.”
There’s a difference between saying that there is no benefit in IF and saying that there MAY be a benefit without caloric restriction, but there’s currently no strong evidence to support this.
You wrote: “Seems to me like you are gathering all the article that supports your claims…”
I can assure you that Myolean Fitness has no biases and we only care about the truth. I can also assure you that we would be extremely happy if new research shows that IF has, without a doubt, health benefits! If you think that there is strong research showing that IF has health benefits in humans in the absence of caloric restriction, please do share it with us 🙂
You wrote: “Ive been following dr. Eric Berg, and what you are claiming completely contradicts what he has been saying for years.”
In my opinion, Eric is not a good source of nutrition information – chiropractors generally get pretty much no nutrition education. Also, a quick Google search suggests that Eric is not a very trustworthy practitioner (https://www.casewatch.org/board/chiro/berg.shtml).
Regarding trying things for yourself, we absolutely recommend that you do!
Also, we are definitely not against IF and, in fact, we have several of our clients on numerous IF protocols. We just prefer to remain objective and unbiased, not letting our feelings regarding any dietary and training approach cloud our scientific opinion of them.
Regarding insulin and sugar level stabilization, the research is mixed. Here’s a quote from an article I wrote for another website:
“One study by Ash et al, for example, reported similar improvements in glycaemic control in 51 men with type 2 diabetes after 12 weeks of intermittent (four days per week) or continuous energy restriction (6).
A 2011 study by Harvie et al which measured hepatic insulin sensitivity in overweight or obese subjects reported a 25% greater reduction in insulin resistance compared to the daily energy restriction group when measured on the morning after five normal feeding days.
It also reported a further 25% reduction in insulin resistance compared with daily energy restriction on the morning after the two energy-restricted days. Importantly, these differences in insulin sensitivity happened despite similar reductions in body fat between the groups (4).
Three other studies that have assessed the effects of 2–3 weeks of whole day fasting and which were designed to ensure that there was no overall energy deficit or weight loss have also reported variable results.
Specifically, the first study by Halberg et al reported improvements in insulin-mediated whole-body glucose uptake and insulin-induced inhibition of adipose tissue lipolysis when measured after two normal feeding days (29), while these results could not be replicated by the Soeters et al study (22).
Interestingly, the third study by Heilbronn et al reported a significant reduction in insulin response and improved glucose uptake and insulin sensitivity in male subjects, whilst female subjects experienced impaired glucose uptake and apparent skeletal muscle insulin resistance (30).
Overall, the limited available research has reported variable effects of intermittent fasting on peripheral and hepatic insulin sensitivity, which may be gender-specific.”
I hope the above helps clear things up!
There’s millions of us Muslims who fast every year. I notice NO health benefit from fasting compared to when I normally eat. I know many other people who fast for religious reasons too. There’s nothing magical about fasting. And I don’t feel better when I fast. I rather not fast but I do it for religious reasons.
Just because it works great for you doesn’t mean it works great for everyone. The best diet will always be the one a person can stick to and enjoy. And IF can make some people binge eat. Not everyone has the same experience.
So your experience does not apply to all people. I notice nothing special about fasting personally.
Does intermittent fasting help to lower ones overall blood pressure ?
Mine is about 130 and I would like to decrease it to 110
Hi James,
When controlling for confounding variables, intermittent fasting on its own doesn’t seem to affect blood pressure (although there’s currently not much research on this).
In general, what seems to reliably help reduce blood pressure is weight loss, exercise, stress management, and a good balance of dietary sodium and potassium (usually, for most people, the former needs to decrease and the latter needs to increase).
I am insulin resistant which messed up my hormones and caused pcos.keto and IF helped me a lot with pcos symptoms. I feel better when I fast.
That’s great to hear, Oishi! Keep it up! 🙂
Makes sense. IF is just a TOOL for fat loss. IF in and of itself does not help you lose weight. It’s the calorie deficit that does. I suppose you can argue that you could IF and still reap the benefits of fasting (numerous ones that you mentioned) and still not lose weight if you’re eating too much during the eating window.
For example, you could eat at a surplus at the end of the day, yet still have upregulation in growth hormone, increase insulin sensitivity, and feel more prductive throughout the day. No reason to not try it out. Although I think in general, people who DO try IF for the first time generally lose weight but they find it harder to consume that many calories in such a short amount of time.
What’s your take on spirulina? I IF every day, but intake about 5g of spirulina in the morning. And then just sip on coffee/preworkout for 8 hours till I’m ready to eat. I’m pretty sure its not kicking my insulin response into overdrive but would love your take on it. Cheers. Thanks!
Hi Ankur,
Thanks for you comment.
Agreed – at this point, it’s pretty much conclusive that intermittent energy restriction helps people lose more fat by making sustaining an energy deficit easier!
With regards to taking spirulina in the morning and then sipping on coffee until you are ready to break your fast, that sounds just fine to me!
I’m so impressed with your research and how well you make this complicated issue understandable to the lay person. I’m also very amazed at your dedication to responding with helpful follow-up!
I am a 71 year old very lean woman who has struggled with hypoglycemia. While I was not at all overweight, I found that an additional 5 pounds made my clothes too tight for comfort. So I tried the IF 16:8 for about 3 weeks, hoping the IF protocol would be a good long-term plan to help cognition and longevity as well as the other touted benefits. I struggled with feeling weak, but I usually made it for 16 hours. Amazingly I lost 8 pounds, which makes me now underweight. Being hypoglycemic, I have always eating a ketogenic diet even before it became popular. Your balanced coverage comparing various models of calorie restriction and IF is causing me to rethink how strict I felt I must be. So in spite of the fact that I still have 2 hours to go in my 16 hour fast, I’m going to celebrate and have a handful of nuts! Thank you!
Thanks for your comment Rhonda,
Great job, keep it up! 🙂
I think this is CLICK BAIT but however. I agree with, the statement, That “everyone can eat whatever as long as there is a calorie deficit”. Unfortunately, a lot of the population are unable to eat high carb diets and control the calorie deficit. The difference in eating certain proportions of the 3 main macros(glucose, protein and fat) is the ability to stave off the hunger that accompanies a calorie deficit. It seems that IF is one of these ways for some, carb restriction for others, and even, high protein for still others, if it was one size fits all there wouldn’t be an obesity problem. Most states in the USA have an obesity problem of up to 35%, that is not counting those with a 25-30 BMI. So cut these people a bit of slack, and have some empathy for their inability to eat 1500 calories of twinkies every day until the are down to their correct weight.
Hello Roy and thank you for your comment.
I agree with what you’re saying, and I’m not sure why you feel that we are saying something different… Can you please paste the exact sentence/phrase where you think that we are suggesting that it’s a good idea to eat 1500 calories of Twinkies every day?
Thanks.
Hi! What is your opinion on Dr Fung’s works? He claims that a calorie is not a calorie.
Hi Helena and thanks for your comment. 🙂
We tackle the argument of “a calorie is not a calorie” here: https://www.myoleanfitness.com/cico-evidence-based-truth/
The whole “ calories in calories out” mindset is missing the Insulin sensitivity issue altogether. It is insulin sensitivity that is the major factor for Body fat increase.
What you eat, “where the calories come from” is the most important factor of the whole equation.
While calorie restriction is relevant it is secondary to blood insulin levels and hormone sensitive lipase.
I wouldn’t suggest fasting if you’re a sugar eater. Every couple of hours you will want to kick a baby in the face.
There is usually plenty of research on both sides of any topic to prove their point. That’s how research works.
If you were looking at intermittent fasting as a way to improve fat loss realize it’s not the intermittent fasting but the decreased insulin level in the blood that allows for hormone sensitive lipase to do it’s job Which is mobilize fat for fuel
Stumbled onto this article while looking at amino acids to minimize lean muscle loss during multiple day fasting.
If you’re fat quit sugar and carbs first. Then re-strict calorie intake.
Hello and thank you for your message.
Unfortunately, there is a large body of scientific evidence which suggests that insulin sensitivity is pretty irrelevant for fat loss and that the primary criterion is, instead, a sustained hypocaloric diet.
For example, here is one study (https://jamanetwork.com/journals/jama/article-abstract/2673150) that aimed to determine the effect of a healthy low-fat (HLF) diet vs a healthy low-carbohydrate (HLC) diet on weight change and if genotype pattern or insulin secretion are related to the dietary effects on weight loss. Here are the conclusions: “In this 12-month weight loss diet study, there was no significant difference in weight change between a healthy low-fat diet vs a healthy low-carbohydrate diet, and neither genotype pattern nor baseline insulin secretion was associated with the dietary effects on weight loss. In the context of these 2 common weight loss diet approaches, neither of the 2 hypothesized predisposing factors was helpful in identifying which diet was better for whom.”
Here is another recent study (https://www.sciencedirect.com/science/article/pii/S0026049516300725), which concluded that “These findings suggest that weight loss itself, rather than diet composition, may be the most critical factor for reducing the chronic inflammation that has been suggested to be a key factor in promoting insulin resistance.”
Thanks again for your comment, and please feel free to reference research to support your position.
Hello and thanks for the useful information. currently i am doing intermittent Fasting by not eating from 6pm to 12pm. Which skips breakfast. I read that skipping breakfast can have a higher rate or heart issues? Are there studies that backs this claim? Is it better to skip dinner instead?
Thanks!
Hello Wu and thanks for your comment.
There is some research which has found an association between skipping breakfast and heart disease. Remember, however, that association does not imply causation. Simply put, it’s probably not that skipping breakfast causes heart disease but, instead, that people who tend to skip breakfast also tend to engage in other behaviors that can increase the risk of heart disease, such as consuming more junk food, not being physically active, and smoking.
I am on Keto but I have a friend that follows IF listening to doctor fung. Very good listen on why caloric deficits are a short term answer but end up slowing base metabolism more.
Hi Rich and thanks for your comment.
To be honest, we don’t think much of Jason Fung. Give this a read and you’ll understand why that is: https://www.myoleanfitness.com/evidence-caloric-restriction/
A few questions.
1. What is the research behind the microbiome’s effects on diets/dieting? I have read that artificial sweeteners have a detrimental effect on your gut microbiome composition and metabolic capacity (nature and science primary articles). Also I have read pop-sci summaries of articles that claim that there likely is a benefit to matching diet to certain people, but this affect get’s lost when taking the average of a study, rather than looking at unique groupings of patient populations, and it may be due to the gut microbiome.
2. What is your understanding on how calories are actually measured in today’s day and age? Is it still bomb calorimetry? If so, are there good metrics to reports utilize-able calories?
A few thoughts to tie these ideas together. I think the types of foods do matter, only such that “whole foods” and good/bad carbs or fats or proteins are just a stand in for how accessible the caloric content it. For example white bread and sprouted grain bread might have the same caloric content as measured by the bomb calorimetry, but accessible calories are drastically different (I know the blood glucose index tries to take account for this, but isn’t systematic for all foods and may complicate the true measure of caloric deficits). So you will get more of a deficit from the sprouted grain. Along these same lines, I think the composition of your gut bacteria also affect how efficiently you process different versions of the same type of foods. Some foods might be “less utilized” by one person than another based on the total metabolic capability of their gut microbioime. Furthermore, there is increased evidence that these bugs alter your cravings etc. There has been incidences of people that get fecal transplants from an obese donor become obese themselves. Again, like your articles states very well, these things likely all come down to the complex questions of actually measuring true calories in vs. calories out. The big thing to me dovetails with your analysis: its all about adherence to a plan of restricted calories- and I imagine some the biggest drivers of breaking diets are cravings related, either from gut microbiome signals, artificial sweeteners messing with cravings, or highly processed foods causing big energy crashes that lead to higher consumptions of food.
One final random point is that my hypothesis for better longevity on fasting is likely repair based. Every time your metabolism is revved up, you are using oxygen and producing free radicals. If you are constantly eating, or never reaching a fasting state, your cells (specifically pancreatic beta cells, etc) never get time to deal with the natural damage that is inevitable from all oxygen utilizing organisms.
As a scientist, I appreciate how you have presented this article- and understand the resistance to it- stemming from people wanting a silver-bullet fix to maintaining a healthy lifestyle.
Hi Will and thanks for your comment,
1. The research on the links between the gut microbiome and obesity is at its infancy and there’s not much we can conclude from it at this point, in my opinion. However, we can safely say that there’s a link between the two. I’m not sure if we can, at this point, say if its an unhealthy gut microbiome that causes obesity or if it’s the other way round. Maybe it’s even both!
With regards to individual differences in the make-up of the gut microbiome and obesity, that’s an ever more specialized topic which definitely needs more research.
In general, my recommendations at this point are pretty simple: try to maintain a “healthy” gut flora by eating foods rich in probiotics and prebiotics, while also avoiding doing things that can kill good bacteria (excessive antibiotic use, excessive drinking, smoking, stress, etc).
2. Regarding the metabolizable energy from different foods, I would recommend you give this a read: http://www.fao.org/docrep/006/Y5022E/y5022e04.htm
Regarding the rest of your comment on how metabolizable energy and individual difference in gut flora are concerned, I agree! 🙂
Regarding fasting and longevity, I also agree. In general, autophagy seems to be the result of low energy availability at a cellular level. The question now is whether intermittent energy restriction has any beneficial effects beyond those that daily energy restriction has.
Again, thanks for your insightful comment. It’s always a pleasure getting comments like yours! 🙂
Can somebody clarify for me. So if I’m intermittent fasting for weigh loss benefits – BCCA drinks will not break my fast?
Hey Joe,
From the article:
“Despite what most people think (and what the nutritional info label on your BCAA product says) ALL BCAA products contain calories. Leucine and isoleucine contain 4.65 calories per gram, while valine contains 4.64 calories per gram. With the typical 2:1:1 ratio of most BCAA products, this means that 10g of BCAAs contain around 46.5 calories.
So yes, BCAAs break your fast. However, it doesn’t really matter if they do or don’t in the first place.”
I’ve just started looking into IF. My main question is about what you can eat. I did read the article and a few comments and responses. I’m wondering, I have a 6 meal a day meal plan made just for me counting macros. Am I to take that meal plan and fit all 6 meals into 2 meals in the given time frame I choose for IF?
Hey Christy,
You can take the 6 meals and fit them into however many meals you want within your feeding window. For most people most of the time, 1-3 meals would make sense, depending on the length of the feeding window.
Out of curiosity:
1. What’s your weight, height, and activity level?
2. What’s your current fitness goal (weight loss/maintenance/gain)
3. What are your target calories and macros?
Hi and thanks for the article!
This was just what I needed to read when I’m on my third day of IF (16:8 protocol) main goal being weight and fat loss. I need to be doing this for the right reasons, which is weight loss achieved by caloric restriction through IF, not the claimed increase in HGH and whatever.
questions:
– what’s your opinion on the magical drink apple cider vinegar and claim that it enhances fat burning?
– training during a fast period vs. during an eating window and does this affect fat burning? I suppose if you can manage training (weight or cardio) during a fasting period, it’s probably ok for you and your muscle gain?
Much obliged!
Hi Ari and thanks for you comment.
Apple Cider Vinegar may slow down gastric emptying and cause a bit of nausea, which means that it can help reduce hunger/make you feel full a bit sooner when eating. Essentially, it may help you eat a little less, thereby creating a caloric deficit. However, it may have negative effects on tooth enamel and on the esophagus and stomach. I would recommend you just put a little vinegar (any vinegar) on your veggies or salad! 🙂
Training fasted increases fat oxidation during training, but your body compensates later in the day by burning less fat and more carbs. This is probably why research has found no beneficial effects of fasted training on body composition: https://jissn.biomedcentral.com/articles/10.1186/s12970-014-0054-7
Hope this helps!
You say that the calorie deficit is what results in weight loss and not necessarily IT, but Dr Fongs research (or referenced research) show that reduced calorie intake causes metabolism to slow and becomes a vicious cycle to keep up with. You reference the old “calories in less than calories out = weight loss” when Dr Fong debunks that in his book. Whos right?
Hello Craig and thank you for your comment,
Dr. Fung isn’t a researcher and has not published any research that I could find.
Regarding the research he references to show that reduced calorie intakes cause metabolic rate to slow down, we actually agree that this is the case. Reducing calorie intake always results in small reductions in metabolic rate. However, these reductions are closer to around 10% and not 40% as Dr. Fung suggests. Dr. Fung is getting these larger numbers because he is using people’s initial weight to calculate metabolic rate, while the honest thing to do is to use people’s new weight.
Regarding the becoming a vicious cycle part, I wouldn’t say that this is accurate. The reason people seem to regain lost weight is because they revert back to their old ways of eating too much junk and not exercising. However, you can’t expect that, once you lose weight, you can revert to your bad dietary habits and keep it off. Successful weight loss and weight loss maintenance is about establishing good habits for the rest of your life, like eating healthy, exercising, monitoring your weight, and having support from your environment.
With regards to the “old” calories in, calories out model, this has never been debunked in any study in the history of ever. I think the problem with CICO is that most people make incorrect assumptions about what it is and what it entails. I would encourage you to read this article on it: https://www.myoleanfitness.com/cico-evidence-based-truth/
Maybe Dr. Fung claims to have debunked CICO in his book. However, he claims so in a “safe space” where other scientists can’t criticize his theories. In fact, at least 99% of the scientific community thinks very little of him, largely due to the fact that he seems to dismiss the energy balance equation which is essentially a rehash of the first law of thermodynamics.
I know that it can be confusing to see all the back-and-forth discussions between obesity experts on the internet and I understand that people are finding it hard to choose who to believe. If it’s any consolation, we are always open to discussion, so you can email us at any time to exchange ideas. 🙂
Thanks for the great article & discussion. I know that there should be a caloric dificit to lose weight on IF, however, i read that if you fast for longer than 12 hours, your body will start using the stored fat for energy, do you agree on that? the reason why i am trying IF now is to eat all my calories in one meal & reduce my carbs in that meal to 25% so that the body will burn this 25% during my fasting and will start burning the fat until i eat. So basically you can say that i am trying to lose fat not weight, or losing fat & maintaining muscles. Do you agree on my approach or you think that i am just wasting my time?
P. S. I am fast for the whole day then i workout fasted at around 7:00 PM then i have my one meal at around 10:00 pm.
Another question, do pre-workouts, multivitamins, fat burners, fish oil, contain calories that will cause the body to produce insulin?
Hello and thank you for your comment!
Okay, so the body doesn’t necessarily only burn fat when you fast longer than 12 hours. The body will burn fat even if you’re eating every 2 hours, provided that it’s receiving less energy than it’s expending, overall. This is reflected in the results of several studies which show that Intermittent Fasting without a caloric deficit (i.e. subjects overeat enough during feeding hours to compensate for the energy deficit) doesn’t result in fat loss. Similarly, research that has subjects eating up to 8 small meals per day reports significant fat loss, provided that a caloric deficit is in place.
Regarding losing fat while maintaining muscle (this will result in weight loss, by the way, since fat has weight), research suggests that this should be done by:
1. Going on a small-moderate, rather than large, deficit,
2. Getting enough protein (around 2 grams per kg of body weight),
3. Performing resistance training with sufficient intensity and volume.
As you can see, the above don’t include recommendations for meal frequency, which means that fat loss and muscle retention can be achieved with, or without, intermittent fasting. This has also been our experience with several of our clients (we have coached people doing a number of IF protocols and successfully got the super lean without muscle loss).
Regarding the supplements you’ve mentioned:
1. Pre workouts: most of these contain calories. Then again, most of them are also a waste of money, since they contain lots of fillers and some good, but underdosed ingredients.
2. Multivitamins: most multivitamin products don’t contain calories. However, the fat-soluble vitamins won’t be absorbed if you take them when fasting.
3. Fat burners: most fat burners don’t contain calories. However, most fat burners are a waste of money.
4. Fish oil: this contains 9 calories per gram.
Please note that insulin is also pretty irrelevant. We explain why in the article above! 🙂
I just popped in here to thank you for having such a scientific approach to this topic, I’m loving the way you’re dealing with the questions and sometimes their less than positive approaches to questioning things. Also, the amount of long answers with such an amount of information is incredible, Keep up the good work!!
Thanks Jaime!
Much appreciated! 🙂
Thank you for the article and for replying to all of the comments. I’ve learned a lot from just that. Do you have any recent articles or anything in the works? Lastly I’ve read a lot of articles suggesting to eating carbs around workouts is the best when on low carb type diets. After reading ur article I would assume that the only apparent benefit would be to increase performance and that nutrient “carb” timing doesnt matter as long as ur in a hypocaloric state when ur main goal is fatloss/muscle retention. So does eating carbs around workout have benefits outside of performance enhancement? Thanks in advance.
Hey Jay,
Thanks – I’m glad to know that the article and comment replies help! 🙂
Regarding your questions:
1. We don’t have anything in the works at the moment.
2. Eating carbs around workouts may help by improving performance and facilitating recovery. As far as I know, there aren’t any other potential benefits.
I just had to add my two cents worth. I speak as a 76 year old guy. When I was young – long, long ago in the Before Times – caloric consumption was tremendously lower than today. We had coffee – not lattes, cappuccinos or other thousand calorie sugar drinks with high octane coffee..
Supermarkets were filled with FOOD – real food. Look around a supermarket today and you will see that 75% of the store is filled with sugar-laden empty calories. Also called junk foods.
Ice cream was a treat – not a daily part of the diet. So was soda. Desserts were desserts not something to be consumed at every meal or INSTEAD OF MEALS.
I guess the message would be – eat as if you are poor. Eat only what you need. Eat for nutrition. Don’t eat for comfort because that turns into grazing which just adds hundreds, if not thousands, of extra, unused calories into your body each day.
Oh, and we moved around more. Office workers had to get up from their desks and actually WALK up or down stairs or to the other end of the building to transact business. We didn’t send emails and sit and wait for a response.
This is spot on! Thanks, Tony!
Accidentally ‘bucked up’ your Site; and I just couldN’T Stop READING ALL Posted here!!!
This ‘forum’ is EXCELLENT!!
And, YU, how yu Patiently ExPlain YOUR side of it all, the Science in it all; just Fascinating..
I do still believe however though, that there’s ‘something’ to that ‘Insulin’ thing (that a few of the folks here have so stated); and I do believe that other Hormone ‘Cortisol’, does have something to do with our Gut being Fat..
I know from all yu’ve explained here, it’s basically Calorie in LESS, than what Expelled out (to achieve that weight loss); but I just don’t know is that’s really ALL it is (shaking my head); as how would one then explain, why the Gut is so hard to loose/can’t loose; nuh matter how do Tummy exercise (the tiny pouch still there (that Fat is still there))??
Anyway, GREAT forum; GOOD Job!!!
Hi Deborah,
Thank you for your comment and for your kind words 🙂
Okay, so what seems to cause “stubborn” fat in some areas of the body (typically belly, love handles, butt, and thighs) is the:
1. High density of alpha-2 adregenic receptors
2. Lower blood flow to those areas
Together, the above make the body fat in those areas of the body more “stubborn”, which is why it’s the last to go (and why it’s so hard to get rid of).
P.S.: A negative energy balance is the primary determinant of changes in body mass, but calories are NOT the only thing that matters! Other things matter too if you care about optimizing health and body composition (e.g., food quality, food processing degree, macronutrient ratios, etc.)
Hope this helps! 🙂