The ketogenic diet is in the spotlight again, both in the research community and in discussions among the general public.
While there is still much to study and learn regarding the use of ketogenic diets for the treatment or prevention of various diseases, the research is pretty clear on how effective they are for fat loss.
After all, the results of the recent metabolic ward study by Hall et al did show that ketogenic diets don’t seem to provide a metabolic advantage or result in a higher rate of fat loss when compared to isocaloric non-ketogenic diets with equal amounts of protein.
Funnily enough, by the way, the study was funded by the Nutrition Science Initiative (NuSI) for the exact purpose of proving that the insulin-carbohydrate theory of obesity holds true and that a ketogenic diet is superior for fat loss.
Well, Gary Taubes, if you are reading this: HA! In your face!
The study above, according to the majority of the scientific community, put the final nail in the coffin of the insulin-carbohydrate theory of obesity.
However, although this may come to you as a surprise, it’s been a little over 40 years since we first got a pretty good indication about how well a ketogenic diet works for fat loss and about how it compares to a non-ketogenic diet.
The ketogenic diet metabolic ward study of 1976
Yep, you read that right.
It was in 1976 when the first metabolic ward study which compared ketogenic to non-ketogenic diets was published in the Journal of Clinical Investigation.
At the time, little research existed on the topic and there were no other studies that directly compared the effects of a hypocaloric ketogenic diet to a hypocaloric non-ketogenic diet on body composition in a metabolic ward setting.
This was exactly what Mei-Uih Yang and Theodore VanItallie from the Department of Medicine and Institute of Human Nutrition of the Columbia University’s College of Physicians and Surgeons set out to investigate.
What the researchers did
The researchers used six obese male subjects, which they studied in a metabolic ward setting for 50 days. The subjects completed 10 days of the following three experimental schedules, each preceded by a 5-day 1200-calorie mixed diet:
- 800-calorie ketogenic diet
- 800-calorie non-ketogenic diet
- starvation diet
Note: Since this article is about comparing a ketogenic diet to a non-ketogenic one, we will simply not deal at all with the starvation schedule – this doesn’t affect the results or conclusions in any way.
With regards to the diets, they were all liquid-based diets and were served to the subjects in four isocaloric feedings at 8:00 am, 11:00 am, 1:00 pm and 6:00 pm.
The composition of the diets was as follows:
- 800 calories
- 50 grams of protein (25%),
- 62 grams of fat (70%) and
- 10 grams of carbohydrates (5%).
- 800 calories
- 50 grams of protein (25%),
- 27 grams of fat (30%) and
- 90 grams of carbohydrates (45%)
Body composition was assessed using the energy-nitrogen balance method, which, essentially, uses the measurement of nitrogen balance to estimate changes in body protein content and then uses energy balance measurements to estimate changes in body fat.
As you can see, the study’s methodology has a few extremely important strong points, including the following:
- The subjects spent the entire 50 days in a metabolic ward and had their meals prepared for them, which means that misreporting of food intake is not a concern as with most free-living studies.
- The ketogenic diet and non-ketogenic diet were isocaloric – their caloric content was the same.
- The protein intake was matched between groups – this is vital, since protein has a high thermic effect which, if not taken into consideration, will distort the results.
A number of things were measured during the study, including nitrogen balance, energy balance, BMR, ketone levels and so on.
As you would expect, there were no statistically significant differences between the ketogenic diet and the non-ketogenic diet for BMR, nitrogen balance or energy balance. There was, of course, a significant difference in the daily excretion rates of ketone bodies, with higher rates observed for the ketogenic diet condition.
Weight loss and body composition
However, what we (and, presumably, you) are mainly concerned about is the weight loss and body composition results, right?
Well, here they are.
Both the ketogenic diet and the non-ketogenic diet resulted in statistically identical changes in body composition, although the ketogenic diet caused more weight loss which, according to the data, was entirely attributed to water weight loss.
To quote the authors:
“…the increment in weight loss exhibited during the ketogenic diet period was due solely to excretion of excess water. Rates of fat loss were not significantly affected by the composition of the diet.”
As you can see in the figure above, both the ketogenic diet and the non ketogenic diet caused the exact same rate of fat loss – however, the ketogenic diet just resulted in a bigger drop in water weight.
If these results sound familiar, that’s because they are identical to the results that Dr Kevin Hall and his colleagues got in their recent metabolic ward study which we mentioned at the start of this article!
Yep, we have had a metabolic ward study since 1976 which compared a ketogenic diet to a non-ketogenic diet while controlling for caloric intake and protein intake and showed absolutely no differences in fat loss.
Beating a dead horse (which insulin didn’t kill)
So, if the research has refuted the insulin-carbohydrate theory of obesity, why are we still beating that dead horse 40-something years later?
Well, it could be because some people are actually making money by having you believe that insulin is the enemy and that they can protect you from it by selling you stuff (we don’t want to point fingers here and the images below of Jason Fung, Gary Taubes and Peter Attia have nothing to do with this).
Conclusions and recommendations
So, with the results of the studies above in mind, what can we conclude?
In our opinion, it’s pretty safe to say that, at least in the short term, a ketogenic diet doesn’t provide a metabolic advantage over a non-ketogenic diet, nor does it result in increased rates of fat loss. It does, however, result in more initial weight loss because of water excretion.
The above, of course, certainly doesn’t mean that ketogenics diet are useless for weight loss. It just means that ketogenic and low carb diets work as well as other dietary approaches for weight loss, provided that they help you achieve a caloric deficit consistently over time.
This goes for any dietary intervention, by the way. Unless your fat loss diet respects your personal preferences and is sustainable in the long term, it won’t result in permanent fat loss.
And that’s pretty much the take home message.
If you want sustainable weight loss, find a diet which you don’t hate and which helps you eat fewer calories than you expend consistently over time, preferably with the majority of your calories coming from minimally-processed, micronutrient-dense foods.
And get enough protein.
And lift weights.
And share this post.