What exercise is actually for

"If I train, can I eat more?" A little — and that is not what training is for.

The arithmetic of one session

An activity's energy cost is its MET value times body weight times time; the app uses the standard compendium for the MET values. A brisk 45-minute walk for an 85-kilogram person is roughly 230 kilocalories gross. Subtract what that person would have used anyway in an ordinary 45 minutes, and the extra is closer to 180. An hour of squash, one of the more demanding sports, is on the order of 650 gross and roughly 580 extra. A large muffin undoes the walk; a pizza undoes the squash. The daily energy calculator shows your own figures, and the app credits sessions at 85 percent of the estimate precisely because planned sessions turn out lighter than planned more often than not.

So exercise can contribute to a deficit, and for people who train a lot it contributes meaningfully. For most people it is a slow way to create one — hours a week for what a smaller portion achieves at every meal — and it comes with a well-documented tendency to eat a little more afterwards.

What it is strong at

Maintenance. People who keep weight off are, as a group, very active — about an hour a day in the registry of long-term maintainers. That is an association from a self-selected sample, but it is the most consistent one in the field, and the mechanism is straightforward: activity raises the level at which you maintain, which makes the maintenance diet less restrictive and more livable.
Composition. A deficit removes fat and lean tissue; resistance training and protein decide the split. This is the reason the strength page exists.
Everything that is not weight. Cardiovascular health, blood pressure, mood, sleep, function in old age — the public-health guidelines are written around these, not around the scale.

What the guidelines actually ask

For adults: a substantial amount of moderate activity every week — the guideline gives a weekly minute range rather than a daily rule — plus muscle-strengthening work on two or more days. Movement spread through the week counts; it does not have to be a "workout". More brings more benefit, up to a point that most people never reach.

What this page does not claim

That exercise is pointless for weight loss — it is a contribution, and for some people the decisive one. That "you can't outrun a bad diet" as a slogan — you can, it is just an expensive way to do it. Or that any figure above is yours: the MET method is a population standard, the guidelines are general guidance, and neither is an individual prescription.

In the app

Planned and completed sessions enter the day's energy model with their MET, minutes and your weight, credited at 85 percent, and change that day's target — not the week's. A recurring schedule keeps them in the plan without re-entering them.

Sources

Physical Activity Guidelines for Americans, 2nd ed. — official public-health guideline
Limitation: обща guidance; не индивидуална exercise prescription
2024 Adult Compendium of Physical Activities — systematic update / primary reference
Limitation: standard MET scoring; 202 rows са estimated; adult edition е 19–59 г.

cited, not reproduced
Wing RR, Phelan S, „Long-term weight loss maintenance“, Am J Clin Nutr 2005;82(1 Suppl):222S–225S — registry summary (National Weight Control Registry)
Limitation: самоизбран регистър, самоотчет; асоциации, не причини; „успелите“ не са представителна извадка

cited, not reproduced

Educational information, not medical advice. It does not replace a consultation with a doctor or a registered dietitian. Not for people under 18, during pregnancy or breastfeeding, or with a history of an eating disorder — talk to a professional first.