Will exercise make me gain weight?


As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)


Just when I thought I’d vanquished this beast (see the most recent Jockology column, “Statistics Canada says being overweight makes you live longer. Should I stop exercising?“), TIME magazine comes out with a cover story called “Why Exercise Won’t Make You Thin” that has been making waves. The author, John Cloud, sifts (somewhat selectively) through several decades of research, and reaches the following conclusion:

In short, it’s what you eat, not how hard you try to work it off, that matters more in losing weight. You should exercise to improve your health, but be warned: fiery spurts of vigorous exercise could lead to weight gain. I love how exercise makes me feel, but tomorrow I might skip the VersaClimber — and skip the blueberry bar that is my usual postexercise reward

The piece has already spawned numerous rebuttals (see this one from Obesity Panacea), along with complaints of misinterpretation from one of the scientists cited. My thoughts? The research he discusses isn’t actually that controversial. For instance, the idea that exercise will actually make you consume more calories than you burn off has been debated for years. (Here‘s a Jockology column I wrote on whether post-exercise eating negates the benefits of exercise.) There are lots of questions that scientists still haven’t nailed down about how diet and activity levels interact to influence health.

What’s way out of whack with Cloud’s article is the conclusion he draws. Somehow the fact that regular exercise doesn’t automatically cause people to lose large amounts of weight gets twisted into an attention-grabbing warning that exercise might actually cause you to gain weight. Where’s the evidence supporting this bold claim? Nowhere. Basically, it reads like the kind of story that has a “bold, counterintuitive” claim that was agreed on at an editorial meeting long before anyone actually did any research.