Intermittent Fasting Can Help You Lose Weight, But Science Says Not For the Reason You Might Think

I have a friend who swears by intermittent fasting for weight lossand weight maintenance. He often cites James Clement, author of The Switch: Ignite Your Metabolism with Intermittent Fasting, Protein Cycling, and Ketowho argues that your body functions best when you allow it to toggle between an “on” and “off” state. To my friend, and to many, the window itself is the trigger: limit the number of hours per day within which you eat, and your metabolism will shift in your weight loss favor.

Or not, as research shows.

In a meta-analysis of multiple studies published by the College of Family Physicians of Canadapeople who adopted intermittent fasting did lose weight… because they also cut the number of calories they consumed.

Makes sense: following a time-restricted eating regimen tends to mean you’ll eat less than you intend. If your eating window is only four hours, it’s hard to wolf down as much food as you would over a more normal ten- or twelve-hour eating window. (My eating “window” is more like a double door, opening around 6 a.m. and closing around 9 p.m.)

The real weight loss power of intermittent fasting? Stick to the regimen, and you very possibly could wind up eating less than you intend.

Research backs that up. A study published in Science Translational Medicine found that participants on an intermittent fasting plan unintentionally consumed 200 less calories per day. (In simple terms, if your plan is to take in no more than 1,800 calories per day, in the event you may only consume 1,600.)

Bottom line? Intermittent fasting alone — toggling from “off” to “on” — doesn’t trigger a metabolic weight loss switch. Intermittent fasting creates a constraint that can result in eating less, which will then trigger weight loss. (Research also shows how many meals you eat a day doesn’t matter; what matters is the total calories you consume, and burn.)