Exercise is the best way to lose weight
Short answerNot the way you think
On this page
Not the way you think. Exercise burns calories, but your body makes up about 28% of what extra activity burns, and a clear loss from exercise alone took more than about 4 hours a week. Food sets the pace on the scale. Exercise does its best work keeping weight off and keeping muscle.
What we’d do
Change what you eat to lose the weight, and keep exercising for everything else. Lift twice a week while you lose, so more of it comes off as fat, and walk most days, since that’s what the people who keep weight off tend to do. Don’t eat back the calories your watch shows. And if the scale is slow, keep going anyway, because your health is changing even when your weight isn’t.
If you remember three things
- The body takes some back. In 1,754 adults, only about 72% of the extra calories burned in activity showed up as extra calories burned that day.
- The guideline dose is a modest loss. 150 to 250 minutes a week prevented gain and gave only modest loss, in the ACSM’s 2009 review.
- Exercise shines after the loss. More than 250 minutes a week went with keeping weight off.
Why it sounds true
Gyms sell it every January, and the machines back them up with a running calorie count. Weight loss shows are built on workouts. And it’s half right, since exercise does burn calories, so it seems like burning more should mean losing more. Then the scale barely moves after a month of hard work, and people decide either that exercise doesn’t work or that something is wrong with them, and neither is the case.
A picture from daily life
Think of paying off a credit card by working overtime while you keep spending the same. You’ll get there, but part of the extra pay goes to taxes, and it’s slow. Spending less gets you there faster, and the overtime helps you stay there.
Exercise is the overtime. It works, the body takes a cut, and food is the spending that decides most of the speed.
What the studies found
The body’s quiet cut
1,754 adults living normal lives, measured with doubly labeled water. Careau and colleagues, Current Biology, 2021
When people were more active, their resting burn dipped to make up for it. On average the body compensated for 28% of the extra activity calories, and more in people with more bodyfat.
People measured once, so nobody knows yet which comes first, the fat or the compensation.
How much it takes
The American College of Sports Medicine position stand, 2009
150 to 250 minutes a week of moderate activity prevented weight gain and gave “only modest weight loss”. More than 250 minutes, just over 4 hours, went with clinically significant loss.
With a moderate diet added, 150 to 250 minutes did improve the loss.
Exercise alone, done right
141 young adults with overweight or obesity, 10 months. Midwest Exercise Trial 2, 2013
Supervised sessions sized to burn 400 or 600 calories, five days a week, with no change in diet. People lost 4% to 6% of their weight, about 8.6 and 11.5 pounds. Controls gained about a pound.
The results count people who did at least 90% of their sessions, under supervision.
Exercise alone can take weight off, at a dose most people don’t do, and more slowly than they hope. Part of the gap between hope and result is the body’s cut, and part is the number on the screen, which is an estimate. How far a watch’s calories can be off, and why eating them back stalls people, are on tdee.guide: Is your watch right about calories? and Eat back your exercise calories.
Where the myth has a point
Exercise is part of losing weight, and a big part of keeping it off. In the ACSM’s review, after a loss, more than 250 minutes a week of activity went with keeping it off, in studies that followed people over time, though no good randomized trial had tested it yet. Lifting “does not enhance weight loss but may increase fat-free mass and increase loss of fat mass”, which means more of what comes off is fat. And the same review found that exercise “without weight loss improves health risk”. The best way to lose weight is mostly food. The best way to keep it off, and stay strong while you do, includes a lot of moving. What exercise can do for your weight.
3 sources
- Careau V and others, Energy compensation and adiposity in humans, Current Biology, 2021europepmc.org
- Donnelly JE and others, American College of Sports Medicine position stand: appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults, Medicine and Science in Sports and Exercise, 2009europepmc.org
- Donnelly JE and others, Aerobic exercise alone results in clinically significant weight loss for men and women: Midwest Exercise Trial 2, Obesity, 2013europepmc.org
