The Problem with Intermittent Fasting


Intermittent fasting (IF) is becoming more and more popular as a weight loss tool. It's less of a diet and more of an eating schedule. There are many ways to do IF and lots of things to consider before starting. (That's where a Naturopathic Doctor can help.)

First, the big question: Does it work for weight loss?

The short answer is yes.

The long answer is more complicated, as is the case with any diet. Most diets result in weight loss (Mediterranean and Paleolithic diets, for example) as long as they are hypo-caloric  - in other words, you eat fewer calories than you burn. IF has the advantage of simplicity: you don't have to follow a strict regiment of do and do-not eat foods, just do and do-not eat time periods. 

These time periods can be broken up many different ways, one of them is alternate day fasting. It's exactly what it sounds like, you eat for one day, and fast for the next. For example, your last meal would be Monday at lunch, and you wouldn't eat again until Tuesday at lunch. One of the more aggressive IF protocols. A lot of this time is spent sleeping, so it's not as bad as it sounds. And that's exactly the schedule used in the following study.

This study had participants follow an alternate day fasting program for 6 weeks [6]. They measured all aspects of the participants intake before and after implementing the IF protocol: from protein, carbs, and fat to vitamin, mineral, and total calories. Participants ate 33% less total calories for the 6 weeks compared to their normal diet. So it comes as no surprise that every measure also came in lower. But did this have any effect on performance?

They found the participants had a lower heart rate during the same level of exercise, a decrease in total energy expenditure, and lower blood lactate (the cause of that burning feeling in your legs). The authors concluded that this was evidence of a performance enhancement. They also reported a 4.4% decrease in body weight and a 15% decrease in body fat mass. That’s good. But there was also a somewhat worrisome result: an almost 3% decrease in muscle mass.  This was likely a result of the reduced protein intake.

So the conclusion? IF might deliver some real benefits, but take precautions: consider taking a multi-vitamin and make sure you are getting enough protein from a wide variety of sources while following an IF regimen.