The Problem with Intermittent Fasting

Intermittent fasting has played a role in helping millions of people lose weight. It is a way of eating that many people feel fits their busy lifestyle, which makes it fairly easy to stay on track. However, there is one main drawback to dieting this way and it is the main reason I try to keep most of my clients and athletes away from this type of diet.


Intermittent fasting works by limiting the amount of time you have to eat. There are several methods to carry out intermittent fasting, with the 16:8 and 5:2 methods being most popular. The 16:8 method allows for 8 hours and eating and 16 hours of fasting everyday while the 5:2 method allows you to eat regularly for 5 days of the week and 2 days of the week you only eat 500-600 calories per day.


The problem is that to build and preserve muscle, we need a steady supply of foods. In a recent study, the 5:2 method was compared to a steady diet. Total calorie intake was similar over a weeks’ time between both diet groups. After 12 weeks, both groups lost the same amount of fat, however, the steady diet group was able to put on muscle on their diet.


Most research shows that if you want to optimize muscle gain or preserve muscle on a diet, you need to be eating around 25 grams of quality protein every 3-5 hours. Our bodies are always breaking down proteins no matter what, and we need to offset that breakdown by increasing what is called protein synthesis (protein building). If we go more than 5 hours without that protein, our body will likely be breaking down more protein than it is building. If we eat our protein every 3-5 hours, we should be building more protein than we are breaking down.


Intermittent fasting causes us to go too long between feeding times and spending too much time breaking down more protein than we are building. Intermittent fasting is also a great way to keep our eating under control and lose/ keep weight off. So, should you try intermittent fasting? If your only goal is to lose weight, go for it. But you want to lose weight while building or keeping muscle mass, there are better options out there.



Chris Still

BS Exercise Science

CSCS, USAW

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