This article was first published in The Montreal Gazette.
When it comes to medical news, the past seven months have been dedicated (for understandable reasons) almost entirely to COVID-19 coverage. When a virus kills more than one million people worldwide, there is good reason why it should be discussed and analyzed in such detail. But there was recently a non-COVID story that slipped under the radar and addresses one of the most frequent questions I used to get before “the event.” A recent study examined whether intermittent fasting helps people lose weight any better than a regular diet. It will amaze many to hear that it does not.
Intermittent fasting has become extremely popular in recent years. It is trendy and the preferred diet strategy of many celebrities who swear by its benefits. For the uninitiated, the basic premise is that you eat nothing (or very little), but only at specific times.
There are many variants of intermittent fasting. Some involve an alternating schedule where you diet one day and then eat normally on the next. There is the 5:2 diet where you would eat normally for five days per week and then eat very little on the other two. Unfortunately, studies testing alternate day fasting and the 5:2 diet have not shown it to be any better than other diets.
Undeterred by these setbacks, new versions of intermittent fasting have gained popularity. Rather than alternate between “feeding” and “fasting” on a daily schedule, these new versions of intermittent fasting tell you to stop eating only for certain hours of the day. The most popular versions usually involve 12 or 16-hour fasts, where you eat as much as you want during the prescribed time and fast for the rest of the day.
However, while a 16-hour fast sounds impressive, it is worth remembering that you are asleep during much of this time. For example, a 16-hour fast may tell you to eat whatever you like between noon and 8 p.m. and then eat nothing from 8 p.m. until lunchtime the following day. But you will be sleeping for much of that time, and most people do not usually eat much past 8 p.m. anyway. In reality, the only real change with this type of diet is that people are asked to skip breakfast, only eat their first meal of the day at lunchtime and, of course, to skip night-time snacks.
While the 16-hour fast is currently trendy, it is really just skipping breakfast by another name. A recent paper in JAMA Internal Medicine compared this type of time-restricted eating to a regular three-meal-a-day schedule and found no difference in weight loss after three months. Indeed, weight loss was relatively modest and was on average less than one kilogram in both groups.
Many people have told me that they have packed on some extra pounds during this pandemic. This is quite understandable, given that people are doing less and staying home more. It may be tempting to try one of the many diets you can see advertised on TV or online. But when it comes to intermittent fasting, it does not seem to be any better (or worse) than any other diet.
In fact, all diets seem to be equally effective (or ineffective depending on your point of view) and most ultimately fail because people abandon diets that are too hard to maintain long term. Diets will work if they get you to eat less throughout the day, regardless of the mechanism. Whether you do it seems to be more important than how you do it, and the best diet is ultimately the one you can stick with.