What can exercise do for your weight?
On this page
Less for the scale than it feels like, and a lot for keeping weight off and keeping muscle. In 1,754 adults, the body made up about 28% of the calories that extra activity burned. A clear loss from exercise alone took more than about 4 hours a week.
This is where most people quit. They start exercising to lose weight, the treadmill says they burned a lot, and after a month of hard work the scale has barely moved. So they decide exercise doesn’t work for them, and they stop, and they lose everything else it was doing too. Others eat back what their watch says they burned and wonder why nothing changes. Exercise takes weight off slowly, and it does a lot of other things well.
What we’d do
Let food set the pace on the scale, and use exercise for the jobs it’s great at. Lift twice a week while you lose weight, so more of what comes off is fat. Walk most days, since the people who keep weight off tend to move a lot. Don’t eat back the calories your watch shows. And judge your exercise by how you feel, your strength and your waist, never only by the scale.
If you remember three things
- The body takes some of it back. Only about 72% of the extra calories burned in activity showed up as extra calories burned that day.
- The guideline dose gives only a modest loss. 150 to 250 minutes a week stopped weight gain, and more than 250 went with a clear loss.
- Keeping it off is where exercise shines. People who kept weight off tended to move more than 250 minutes a week.
Why does the scale move less than the treadmill says?
In 2021, a team of researchers pooled the largest set of measurements ever collected of how many calories adults burn in a day, using a lab method called doubly labeled water, in 1,754 people living normal lives. They compared each person’s total burn with their resting burn and their activity. When people were more active, their resting burn dipped a little to compensate. On average, the body made up 28% of the extra activity calories, so “only 72% of the extra calories we burn from additional activity translates into extra calories burned that day.”
The size of that compensation varied a lot between people, and it was bigger in people with more bodyfat. Nobody knows yet whether that’s because people who compensate more tend to gain fat, or because the body compensates more as it gains fat.
That’s before the second problem, which is that the burn on the screen is an estimate. How far a watch’s calorie number can be off is on tdee.guide, and why eating it back stalls people is in Eat back your exercise calories.
A picture from daily life
Think of a raise at work. You get an extra $100 a week, and about $72 of it shows up in your paycheck after tax. You’re better off, and it’s still less than the number in the offer letter.
Exercise works like that. You do burn more, and you keep most of it. The body takes the rest back, and that’s why the scale moves slower than the screen promised.
How much exercise does it take to lose weight?
More than most people do. In 2009 the American College of Sports Medicine reviewed a decade of studies. Its position stand found that 150 to 250 minutes a week of moderate activity was enough to prevent weight gain but would “provide only modest weight loss”. More than 250 minutes a week, just over 4 hours, went with clinically significant weight loss. With a moderate diet on top, 150 to 250 minutes did improve the loss.
Exercise alone, at a big dose
141 young adults with overweight or obesity, average age 23, 10 months. Donnelly and colleagues, Obesity, 2013 (Midwest Exercise Trial 2)
Supervised sessions sized to burn 400 or 600 calories, five days a week, with no change to what they ate. People who did their sessions lost about 8.6 and 11.5 pounds (3.9 and 5.2 kg), 4% to 6% of their weight. The control group gained about a pound.
The results count people who did at least 90% of their sessions, five days a week under supervision for ten months.
The review behind the guideline
The ACSM position stand on weight loss and regain, 2009
150 to 250 minutes a week prevented gain and gave a modest loss. More than 250 minutes went with a clear loss. After a loss, more than 250 minutes a week went with keeping it off.
”No evidence from well-designed randomized controlled trials” exists yet for preventing regain.
A big, steady dose of exercise does take weight off on its own, and it’s slower than most people hope. The calorie side is tdee.guide’s subject, and fat loss in full is on bodyfat.guide.
What exercise is great at
- Keeping weight off. In studies that followed people after a loss, more than 250 minutes a week of activity went with keeping it off, though nobody has tested it in a good randomized trial.
- Keeping muscle while you lose. Lifting “does not enhance weight loss but may increase fat-free mass and increase loss of fat mass”, in the ACSM’s words, which is the trade you want when you’re losing weight. Why lift if you already walk?
- Your health, whatever the scale says. The same review found that endurance exercise or lifting “without weight loss improves health risk”.
Is cardio or lifting better for weight loss?
They do different jobs, and bodyfat.guide has the trials that compared them for fat loss in Is cardio or lifting better for fat loss? On a GLP-1, put strength first, since part of what you lose can be muscle. How should I exercise on a GLP-1?
Doesn’t that mean exercise doesn’t work for weight?
The case against
The loss is small for the work. At the guideline’s 150 minutes the loss was modest, and the body takes back about 28% of the extra burn.
The case for
It works at a bigger dose, and it holds the loss. Five supervised sessions a week took off 4% to 6% of weight with no diet at all. People who kept weight off moved more than 250 minutes a week. And the health benefits came regardless of the scale.
What we still don’t know
Whether moving more keeps weight off, or people who keep it off just move more, hasn’t been settled by a randomized trial. The compensation figure is an average across people measured once, not the same people followed before and after starting exercise.
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
