What Exercise Can and Can't Do for Your Weight
It's not the fastest way to lose weight, but it's one of the best ways to keep it off, and possibly the best thing you can do for your health overall.
The short version
- Exercise alone usually produces modest weight loss. Food changes usually do more of the work.
- It's strongly linked with keeping weight off, and it protects muscle while you're losing.
- The target for adults is 150 to 300 minutes of moderate activity a week, plus strength training twice a week.
- Exercise improves your health even if the scale doesn't budge.
Why it's slower than you'd think
A 30-minute brisk walk burns about 100 to 200 calories, depending on your size. That's about a slice of toast with peanut butter. Your body also partly compensates: you might feel hungrier, or move less for the rest of the day. So exercise alone tends to produce a small weight loss, usually only a few pounds unless the amount is high.
That doesn't make it less worthwhile. It just means weight probably isn't the best thing to judge it by.
What it does brilliantly
- Helps keep weight off. Regular activity is among the strongest predictors of maintaining weight loss.
- Protects muscle while dieting. In a trial of older adults on a diet, those who combined aerobic and resistance exercise improved physical function the most, and they kept more muscle and bone than those who only did aerobic exercise.
- Lowers disease risk. Heart disease, stroke, type 2 diabetes, several cancers, depression and dementia.
- Improves your blood sugar and blood pressure. Often within days to weeks, and even without weight loss.
- Improves your sleep and mood. Which makes everything else easier.
How much?
| Goal | Amount a week |
|---|---|
| Baseline health | 150 to 300 min moderate, or 75 to 150 min vigorous, plus 2 days of strength training |
| Modest weight loss | About 150 to 250 min of moderate activity |
| Bigger weight loss, or keeping it off | About 250 to 300+ min of moderate activity |
Moderate means you can talk but can't sing, as in a brisk walk. Vigorous means you can say only a few words at a time.
These are targets, not entry requirements. Going from nothing to a 10-minute walk a day is the biggest health jump you can make.
Cardio or weights?
You want both, for different reasons:
- Cardio (walking, cycling, swimming) burns more calories in the moment, and helps your heart.
- Strength training preserves muscle, strengthens bones, and keeps you capable as you age.
If you're a beginner and can only do one, start with whichever you'll actually do. Walking is a great default. Add strength training as soon as you can.
Common traps
- Eating it back. A workout can feel like it earned you a muffin, and that muffin may be bigger than the workout. Fitness trackers often overestimate your burn, too.
- Doing too much too soon. Injury sets you back for weeks. Build slowly.
- Using it as punishment. Exercising to make up for food tends to backfire. Move because of what it gives you.
- Hating what you do. You'll be more consistent with something you enjoy. Dancing, hiking, swimming and playing with your kids all count.
Sources
- CDC: Physical Activity Guidelines for Adults
- CDC: Benefits of Physical Activity
- Donnelly et al., Med Sci Sports Exerc (2009): ACSM position stand on physical activity and weight
- Swift et al., Prog Cardiovasc Dis (2014): Exercise and physical activity in weight loss and maintenance
- Villareal et al., NEJM (2017): Aerobic or resistance exercise, or both, in dieting older adults
This guide is general information, not medical advice. Please check with a clinician before making big changes, especially if you have a health condition, take medication, or are pregnant. Read the full disclaimer.
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