April 29th, 2017|Fat Loss, Nutrition|
The Evidence for Caloric Restriction - Myolean Fitness

So a few weeks ago, we published an infographic which showed that all weight loss diets work through caloric restriction and, consequently, through the resulting caloric deficit.

A few people objected to it, saying that body composition and health are not just about a caloric deficit but, rather, also about food quality.

Here’s the thing: WE AGREE 100%!

We’ve actually gone out of our way several times in a few articles to make this point crystal clear. We even mentioned it in the first article we ever published, where we talked about the “secret” to fat loss.

The Evidence for Caloric Restriction - How Diets Work - Myolean Fitness

So no disagreement there. For optimal health and body composition, things like macronutrient amounts, fiber intake, food quality, meal timing and so on are important.

This is, of course, why the majority of the calories in our custom-made sample meal plans, that are part of the online fitness coaching services we provide, come from minimally-processed, micronutrient-dense foods.

The above shouldn’t, however, distract us from the fact that for a net increase or decrease in the body’s energy stores to take place, an imbalance between energy intake (from food) and energy output (from activity) must happen.

Practically speaking, for fat loss to occur, caloric restriction has to take place (or at least an increase in energy expenditure without a concomitant increase in caloric intake).

This is something that is objectively true and which the entire scientific community agrees on, by the way.

Strangely enough, however, an obesity doctor (well, a nephrologist, in reality) seems to disagree.

A ranty post by Dr. Fung

So a few days after the above infographic was published, Dr. Jason Fung responded with a ranty post on his blog (which you can read here) essentially claiming that caloric restriction doesn’t work for weight loss in the long term.

Now, if you go through his entire article, you’ll notice that his argument essentially boils down to that caloric restriction doesn’t work for weight loss in the long term, despite people adhering to their diets. 

He even shares a couple of graphs from a few studies which show that, initially, weight loss occurs during calorically restricted diets, but then weight regain happens as weight slowly creeps back up during the months and years that follow.

Although Dr. Fung doesn’t offer an explanation as to why the weight is regained despite the subjects complying to their diets, he seems to suggest that this happens because of a decrease in energy expenditure.

Let’s not get ahead of ourselves, though. Let’s analyze Dr. Fung’s points one by one.

Changes in metabolic rate with caloric restriction

After the first paragraph, Dr. Fung goes on to talk about energy balance and the First Law of Thermodynamics, essentially agreeing that it always holds true.

He goes on to state that (and these are direct quotes, by the way):

  • “If you eat less calories, you will burn less. So there is no overall change in body fatness”

and that

  • “Basal metabolism may increase or decrease up to 40%.”

So are the above statements true?

Well, they are mostly inaccurate, although they have an ounce of truth to them. It’s true that caloric restriction results in a decrease in energy expenditure and that hypercaloric diets result in an increase in energy expenditure. However, the statement that the basal metabolism (i.e. BMR/RMR) may increase or decrease by up to 40% is not supported by any scientific research. 

So how much does BMR/RMR increase/decrease with over- and underfeeding?

With regards to overfeeding, the largest BMR increase that we have found in studies lasting at least 2 weeks (and after adjusting for weight gain) is around 17% – i.e. nowhere near the 40% that Dr. Fung claims. Moreover, this scientific research paper suggests that the average BMR increase with overfeeding to be around 10%.

What happens to our metabolic rate with caloric restriction (underfeeding) then?

From what we could find, the largest drop in RMR in weight-stable conditions (and after adjusting for weight loss) was seen in the Minnesota Starvation Experiment, which recorded a (drumroll…) 15% drop in metabolic rate. Yep, still nowhere near the 40% which Dr. Fung claims. It’s also worth noting that this was a semi-starvation study, where subjects were in a severe caloric deficit until they reached around 4% body fat.

So where did Dr. Fung go wrong in his calculations? 

Well, Dr. Fung probably failed to consider that reductions in metabolic rate should account for weight loss or gain, since a smaller body will burn fewer calories and a larger body will burn more. So, when weight loss occurs, the honest thing to do is to compare the new BMR to the predicted new BMR (based on the reduced body weight) and not to the old one (i.e. before weight loss had occurred).

On a relevant note, as you can see in the table below, science has a pretty good idea about how much different components of the human body contribute towards the metabolic rate.

Dr. Fung’s CRaP

In the next paragraph, Dr. Fung refers to the approach of caloric restriction for weight loss as CRaP (Caloric Reduction as Primary).

If you delve a little more into it by reading more articles on his blog, you’ll notice that he is, essentially, making a number of assumptions on what he thinks researchers and fitness professionals think, and then basing his arguments on that.

More specifically, Dr. Fung thinks that we think that:

  • a change in one side of the energy balance doesn’t cause a change in the other
  • food intake is not affected by hunger, hedonic, sociocultural and other variables
  • exercise (or TEA) is a major component of total energy expenditure
  • the endocrine system is not involved in the regulation of adipose tissue

In reality, however, no respected nutritionist, dietitian, or fitness professional thinks that the above issues relating to the CICO (calories in, calories out) model hold true.

Weight loss and long-term maintenance

Dr. Fung continues by asking the following question:

“So, where is the evidence that reducing calorie intake as the primary strategy results in long term meaningful weight loss?”

Okay, so let’s see what scientific evidence we have:

This 10-year observational study of 2886 men and women found that, after 10 years, average weight loss with caloric restriction and an increase in activity was around 50 pounds.

The researchers reported that “decreases in leisure-time physical activity, dietary restraint, and frequency of self-weighing and increases in the percentage of energy intake from fat and disinhibition were associated with greater weight regain.”

Essentially, weight loss success in the long term was found to be associated with staying active, controlling caloric intake, keeping track of body weight and not eating huge amounts of fat.

The authors also reported that “long-term weight-loss maintenance is possible and requires sustained behavior change”.

Truly ground-breaking stuff!

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Why do people regain lost weight?

Dr. Fung continues by presenting a couple of studies (along with a few graphs), which show that a large proportion of the weight lost by most subjects is regained in the years that follow.

Here’s the thing: we’re not saying that people always succeed in losing weight and keeping it off. Quite to the contrary. Most people seem to regain much of the lost weight after a few months and years.

Here’s where Dr. Fung is being brutally dishonest, however (or, at the very least, embarrassingly misinformed): He claims that, in those studies, weight regain happened despite subjects adhering to their diets.

Here are a couple of direct quotes from his article:

  • “In a pattern familiar to every person who has ever dieted, the weight starts to regain despite continued compliance to the diet”
  • “Also, it is important to note that women did, in fact, stick to their calorie reduced diet. Yet the weight regain still happened. BUT it wasn’t because of non compliance.”

This is where we strongly disagree with Dr. Fung, since a large body of scientific evidence clearly shows that weight regain happens exactly because of lower dietary adherence and poor compliance over time.

First and foremost, here is some research which compared different diets (Atkins, Ornish, Weight Watchers and Zone) and which found that adherence to caloric restriction (even when it’s self-reported) plummets over time.

Here’s one of our favorite quotes: “in the long run, sustained adherence to a diet rather than diet type was the key predictor of weight loss and cardiac risk factor reduction in our study.”

Here’s a table from the same study, showing that all diet interventions resulted in meaningful weight loss at the start, but weight regain slowly started to take place as the months passed, evidently because of lower dietary adherence.

Finally, here’s a graph from the same study showing that there is a statistically significant correlation between weight loss and dietary adherence.

Moreover, here’s a recent meta-analysis which compared weight loss between low and high carbohydrate diets (and included 7286 individuals) and found no significant weight loss differences between the diets after 12 months.

The researchers concluded that: “significant weight loss was observed with any low-carbohydrate or low-fat diet. Weight loss differences between individual named diets were small. This supports the practice of recommending any diet that a patient will adhere to in order to lose weight.”

Here are a few more of our favorite quotes from the study:

“These findings support recent recommendations for weight loss in that most calorie-reducing diets result in clinically important weight loss as long as the diet is maintained”


“because different diets are variably tolerated by individuals, the ideal diet is the one that is best adhered to by individuals so that they can stay on the diet as long as possible.”

Notice a common pattern there? Yep, dietary adherence TRUMPS everything else.

We won’t bore you with any more studies by the way. The above is a meta-analysis and is literally loaded with references you can check out yourself.

Conclusions and recommendations

So here are our conclusions and recommendations. Sadly, they are neither ground-breaking nor book-selling, but that’s life.

The focus of ANY weight loss intervention should be to create a caloric deficit with a diet that is:

  • composed primarily of minimally-processed, micronutrient dense foods
  • has enough protein to prevent losses in lean body mass
  • doesn’t create deficiencies in micronutrients
  • honors the individual’s personal preferences with regards to meal timing, food choice, and so on
  • can be adhered to in the long term
  • promotes a healthy relationship with food

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