The keto diet has been around for a long time. Still, recently its gaining popularity again, especially for weight loss purposes.
But is keto good for weight loss?
And while there is still a great deal to investigate and learn about ketogenic nutrition in the context of treatment and prevention of a variety of diseases, research on ketogenic diet for weight loss (aka fat loss) is quite clear.
The recent study by Hall et al. (2016), conducted in a metabolic chamber, demonstrated that ketogenic diets do not confer metabolic benefit or greater body fat loss than an isocaloric non-ketogenic diet with identical protein intake.
Ironically, this study was funded by the Nutrition Science Initiative (NuSI) to prove just the opposite, highlighting that the insulin-carbohydrate theory of obesity is true and that a ketogenic diet is a superior alternative in terms of fat loss.
Although this may be some sort of startling news for you, it’s now been 40 years since we learned how effective a ketogenic diet is in terms of fat loss compared to a non-ketogenic diet.
Ketogenic diet for weight loss: What science has taught us 40 years ago
Yes, you read that right.
It was the year 1976 when the first study examining the ketogenic diet with a non-ketogenic diet in a metabolic ward was published in the Journal of Clinical Investigation.
There was very little research in the field at that time, and there have been no studies examining the direct effects of a hypocaloric ketogenic diet on a hypocaloric non-ketogenic diet with respect to body composition in such a metabolic chamber setting.
But this was exactly what Mei-Uih Yang and Theodore Van Itallie of the Department of Medicine at the Institute of Human Nutrition at the Columbia University College of Physicians and Surgeons did.
The scientists recruited 6 male, overweight subjects, who studied them in a metabolic chamber for a period of 50 days. Participants completed one of the following three experimental schedules for 10 days each, with each phase preceded by a 5-day diet of 1,200 kcal (mixed diet).
- Ketogenic diet with 800 kcal per day.
- Non-ketogenic diet with 800 kcal per day.
- Hunger Diet (“Starvation Diet”).
Note: Since this article compares between a ketogenic diet and a non-ketogenic diet, we ignore all the starvation stuff. This does not affect the results and conclusions that can be drawn from it.
At the nutritional forms should be mentioned at this point that it was liquid food. The “meals” were served by the participants at four different times during the day: 8 am, 11 am, 1 pm and 6 pm.
The composition of the diet looked like this:
- 800 kcal
- 50g protein (25%)
- 62g fat (70%)
- 10g carbohydrates (5%)
- Non-ketogenic diet
Non keto diet:
- 800 kcal
- 50g protein (25%)
- 27g fat (30%)
- 90g carbs (45%)
The body composition was analyzed by the Energy-Nitrogen Balance method, which, essentially, uses a measurement to calculate an estimate of the change in body protein content and then provides an energy balance measurement to determine a change in body fat content.
As you can already see, this study has some strengths, including:
The participants spent the entire time (50 days) in the metabolic chamber and received prepared meals, which means that there can be no misrepresentation regarding food intake (a problem that occurs in “free-living” situations).
The ketogenic diet and non-ketogenic diet were isocaloric, i. the calorie content was exactly the same.
Protein intake was identical in both groups. This is an important aspect since protein has a very high thermal effect which, if not taken into account, can lead to distorted final results.
Researchers performed numerous measurements during the study, including those on nitrogen balance, energy balance, basal metabolic rate (BMR, ketone body concentration, etc.).
As one might expect, there were no statistically significant differences between the ketogenic diet and the non-ketogenic diet in terms of metabolic rate, nitrogen balance, and energy balance. However, there was, of course, a significant difference in the daily excretion amount of ketone bodies, with a higher rate found during the ketogenic diet.
Well, here are the results:
Both diets, both the ketogenic diet and the non-ketogenic diet, led to identical statistical changes in body composition, with the weight decreasing more during the ketogenic diet, which, the data suggests, is due to higher water loss (carbohydrates / Glycogen binds intracellular water Less glycogen = less stored water in the body = less weight, but this should not be confused with fat loss!).
To quote the authors:
“… the increment in weight loss exhibited during the ketogenic period. Rates of fat loss were not affected by the composition of the diet. “- Ying & Van Itallie, 1976
As you can see from the above graphics, both diets lead to an identical fat loss. The excretion of body water, however, was more pronounced in the ketogenic diet.
With the above study results in mind, you’re probably wondering which conclusion we get, right?
In the short term, it is almost certain that a ketogenic diet will not provide a metabolic advantage over a non-ketogenic diet and will not contribute to a higher level of fat loss. It is true, however, that the weight of a ketogenic diet decreases faster, which is simply related to a higher excretion rate of body water. However, this body water returns (is re-stored) when carbohydrates are reintroduced into the diet.
Of course, such a statement does not mean that ketogenic diets and diets are useless when it comes to losing weight and fat. It just means that ketogenic diets and low carb diets work just as well as other dietary approaches, as long as they help you to maintain a calorie deficit for a long time.
By the way: this applies to any nutritional intervention. Unless your dieting approach takes into account your personal preferences and is sustainable in the long run, you will not achieve groundbreaking results in terms of fat loss.
And that is also the take-home message of this article.
If you’re looking for sustainable fat loss, you should find a form of diet that you do not hate and that will help you eat fewer calories than you consume-ideally, the calories you get will come from minimally processed, micronutrient-rich foods.
And make sure you eat enough protein.
And train with weights.