There was an interesting study done back in the mid 1970’s. The study may not be possible today since there may now be ethical issues about starving people. We seem to have a fear of fasting that fails to take into account our human history of long fasts and famines.
|Diet/Intervention||Weight Loss||Water Loss||Fat Loss||Protein Loss|
|Ketogenic Diet||466 g/day||61.20%||35.00%||3.80%|
|Mixed diet||278 g/day||37.10%||59.50%||3.40%|
|Weight Loss||Water Loss||Fat Loss||Protein Loss|
|Ketogenic Diet||466.6 g/day||285.6||163.3||17.7|
|Mixed diet||277.9 g/day||103.1||165.4||9.4|
Ketogenic vs Mixed Diet
Once again the Ketogenic diet is shown to be more effective at weight loss than a mixed diet. However, the different is almost entirely made up of a much larger water loss on the keto diet than on the mixed diet. Looking at the grams per day of fat loss (the only thing that really matters in weight loss) the keto diet and the mixed diet are almost identical. Protein losses were equivalent on both the Keto and Mixed diets so there’s not much of an advantage to either. In the case of Keto vs Mixed it might just come down to which diet is easier to comply with and Keto wins that hands down for most people.
Fasting vs Ketogenic Diet
The results here show that a person can lose more weight fasting than they can even with either a ketogenic or a mixed diet. After all, they are eating nothing while fasting. Fasting produced almost three times the weight loss of the mixed diet. And when it comes to fat loss, fasting also wins hands down with a 1/3 greater amount of fat lost.
However, protein losses while fasting are almost twice those of the ketogenic diet on a percentage basis. The loss of 50g of Protein a day is almost two ounces of protein per day. That could be a significant amount for someone and is not a great preservation of Lean Body Mass.
The answer here may be found in the subjects themselves. They were six grossly obese males. The mean weight was 140 kg (308 lbs). They were great subjects for fasting since they had more than enough fat mass to support a ten day fast.
Fasting was slightly better about not having as much water loss as the Keto diet but Fasting was not as effective for weight loss as a percentage of weight lost.
What Does This Study Say About Fasting?
- Fasting produces the quickest weight loss of any of these three methods.
- Over 60% of the weight lost during a fast was water weight. This was the same for the Ketogenic diet. A mixed diet with carbohydrates is better at holding onto water. Much, it not all, of water weight is quickly regained after leaving the any diet.
- Fasting does not spare Protein as well as the Ketogenic diet. In fact, it is about twice as bad at preserving Protein.