There is a lot of debate about the potential health benefits of intermittent fasting. There is a certain group of people who have become extraordinarily passionate about this technique and now believe it to be an almost universal cure-all. With one of their most oft-cited claims being that intermittent fasting has special benefits for weight loss. I have previously addressed intermittent fasting here and here.
Weight loss is a big reason that leads most people to intermittent fasting. There is significant anecdotal evidence that intermittent fasting can help some people lose weight, the question is whether or not there is evidence of clinically or physiologically superior weight loss. This is also quite possibly the most difficult of the potential health benefits to unpack.
This study does show consistent weight loss among people using alternate day fasting. Alternate day fasting is where 25% of the maintenance calories are consumed every other day, with free feeding on the other day. However, it is important to remember that this was a very small study done on obese people. Interestingly though, almost all of the weight lost seems to have come from fat, with a negligible other mass loss. However, due to the small size of the study and the relatively short length it is hard to say with any degree of certainty that intermittent fasting contributed to their weight loss, especially since it was not controlled against a normal calorie restricted diet.
This study which used a more severe version of alternate day fasting in which every other day eating was not permitted also showed significant weight loss. But again we are plagued by small study size and the fact that it is not controlled against a calorie restricted diet so it is very difficult to attribute any changes to intermittent fasting. Also this study showed an increase in hunger for intermittent fasting.
In order to find one that controlled against other types of diets I found this study which found that the amount of weight loss was the same for intermittent fasting as it was for other interventions. Suggesting that there is no specific physiological benefit to intermittent fasting in terms of weight loss. This was also a slightly larger study which makes me feel more comfortable in trusting its results.
However, there are so many success stories with intermittent fasting that I still wondered if there might be some benefit that was getting lost based on the study design so I kept looking. This larger study on overweight women found that intermittent fasting did support greater weight loss than simple caloric restriction. Thus suggesting that perhaps there is some benefit to intermittent fasting.
However, this still did not seem to be a huge change. So I spent some more time going over studies and found this study and this study that both showed no significant difference and this study and this study that both concluded intermittent fasting may be a superior technique.
So basically my review of the literature has concluded that there may be an advantage to intermittent fasting. I know that is not a very satisfying answer but there is still enough contention for it to be impractical for me to make any conclusions. Which means that do not use intermittent fasting as some miraculous tool for weight loss. Use intermittent fasting if it works for you as a better method to control your caloric intake or for the psychological benefits I already discussed.
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