Is the Ketogenic Diet the Holy Grail of Fat Loss? A Review of Recent Literature

Is the Ketogenic Diet the Holy Grail of Fat Loss? A Review of Recent Literature

In a world plagued with vanity and the race to look better than everyone else, we will stop at nothing to find the fastest and easiest method to get there. The topic today: diets—specifically, ketogenic diets vs conventional diets.

If you haven’t been living under a rock, you’ve most likely heard of this type of diet, which is also known as a low-carb diet. The low-carb and keto zealots will do everything in their power to convince you that there is no easier, better, and faster way to a slim body because in their mind, it’s a specific macronutrient that causes excess weight gain—carbohydrates.

Although this sounds like the new diet revolution, the idea isn’t new. Dr. Robert Atkins popularized the idea of a low-carb diet for weight loss in his bestselling diet book “The Atkins Diet”.

The idea is simple; when you cut carbohydrates from your diet and make up the rest in fat, your body has no choice but to use dietary and your own body fat for fuel. What happens when your body starts to use fat for fuel? You become a fat-burning machine—and fast! The ketogenic diet also purports to increase energy expenditure by 300-600 calories/day. If this is true, fat loss should theoretically, be effortless.

At least that’s what they say. From the title, you can expect that I’ll have the actual evidence to determine whether the Ketogenic diet is the be all end all when it comes to dieting or whether it’s just another extreme diet, with extreme promises of getting you extremely skinny. So, let’s begin.

In the study done by Hall et al in 2016 (PDF here), they examined the effects of a ketogenic diet on body composition and energy expenditure on overweight and obese men.

Study Protocol

The study had 17 participants between the ages of 18 and 50 with a BMI between 25 and 35 (obese and overweight) and admitted them to a metabolic ward for compliance reasons. The researchers wanted to make sure the participants ate the food that was provided to them to be as accurate as possible. Everyone was assigned 90 minutes of aerobic exercise and followed a diet that consisted of a higher carbohydrate intake aimed at mimicking the habitual diet of the modern world and a low-carb ketogenic diet. Protein was constant between the two diets.

Here is a snapshot of the calorie and macronutrient data:

 

 Results

Body Weight & Composition

The participants lost .8 ± .2 kg (or 1.76 lbs.) over the last 15 days of the higher carbohydrate diet with .5 ± .1 kg (or 1.1 lbs.) coming from actual body fat. This translated to a daily calorie deficit of 373 ± 97 calories/day. When the participants underwent the Ketogenic diet, they initially lost a rapid 1.6 ± .2 kg (or 3.52 lbs.) in the first 15 days (Holy cow!).

However, fat mass decreased by only .2 ± .1 kg (or .44 lbs.) over the last 15 days, with a total weight loss of 2.2 ± .3 kg (or 4.8 lbs.) over the entire 28-day period and a total of .5 ± .2 kg (or 1.1 lbs.) of actual body fat lost. This equated to a daily deficit of 242 ± 94 calories/day with the researchers concluding that it wasn’t significantly different vs. the higher carbohydrate diet.

Energy expenditure

Energy expenditure was measured using a metabolic chamber and doubly labeled water. On the last 2 weeks of the higher carb diet, the participants’ energy expenditure (measured using the chamber) was 2619 ± 93 calories/day which was a little less than what they were eating, which was 2739 ± 108 calories/day.

When measured using doubly labeled water, the participants’ energy expenditure was 2995 ± 45 calories/day which was greater than what was measured with the chamber (2619 ± 93 calories/day). Using the data from the doubly labeled water, researchers confirmed the daily deficit to be 251 ± 84 calories/day which is close to the deficit when calculated using the changes in body composition—which was 373 ± 97 calories/day. What’s important is that researchers concluded that the deficit was due to increased physical activity on non-chamber days which was evident because the participants’ hip accelerometers registered a 21% ± 4% increase in non-chamber days.

Energy expenditure, measured using the chamber for the ketogenic phase was 2676 ± 93 calories/day (a nonsignificant 57 ± 13 calories/day increase over the high carb diet). However, after adjusting for body weight changes that number was more like 100 calories/day (96 if you want to be precise) over the high carb diet. When measured using doubly labeled water, the values were 3146 ± 45 (151 ± 65 calories/day higher than the high carb diet). Win for Keto right? Not necessarily. In the table below, you can see that even though energy expenditure was greater on keto, you’ll notice that spontaneous physical activity (SPA) and Physical Activity of Exercise (PAE) on chamber days were greater on the higher carb diet. Which most likely explains the similar losses in bodyfat.

Additionally, even with greater energy expenditure and lower insulin secretion, the ketogenic diet also increased protein utilization by 1.5 grams/day vs the higher carb diet for the first week until day 11, with norepinephrine and adrenaline also being lower vs higher carb. Data is provided below:

Summary

Overall, researchers found no significant difference in fat loss when comparing a low-carb ketogenic diet vs a conventional higher carb diet. Although total weight loss was higher in the ketogenic diet than in a higher carb diet, 2.2 vs .8 kg respectively, actual body fat loss was the same at -.5 kg.

The ketogenic diet favored increased energy expenditure vs higher carb with a 100 calorie increase but was not significant. Further, even with increased energy expenditure vs higher carb, spontaneous physical activity (SPA) and physical activity of exercise (PAE) in chamber days were lower which negates any advantage in energy expenditure. Additionally, the ketogenic diet led to increased protein utilization vs higher carb by 1.5 grams/day for the first week that continued until the 11th day.

So, when you hear or read anything about the magical diet that works wonders in getting you the body you want, be skeptical. No diet will provide any shortcuts to the body of your dreams. The only thing necessary is a definitive plan and execution. Follow any diet you feel that you can be consistent with but understand that not one diet is better than the other. Consistency is key.

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