I have three DEXA scans on the same scanner at twelve-week intervals, fasted, same time of day.
I would like the mechanism, because I want to be able to reason about the cases nobody has written about.
I have tried to reason it out from first principles and got to two contradictory conclusions.
Can someone derive this rather than assert it?
The short version: cardiovascular exercise for health and maintenance, resistance training for composition, and diet for the deficit.
In this population, exercise capacity often improves quickly with weight loss, which makes the early weeks the wrong time to fix a long-term programme.
To be exact about it, non-exercise activity thermogenesis varies between individuals by hundreds of kilocalories a day and falls during energy restriction, which is a large and invisible term in the equation.
Cardiorespiratory fitness as an independent mortality predictor is established across multiple large prospective cohorts.
The caveat is that anyone with cardiovascular disease or significant deconditioning should get advice before beginning a programme.
Steps are the least-compensated expenditure. Add those first.
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Browse resultsAnswering this needs to distinguish exercise energy expenditure from total daily expenditure, which do not move together as much as they should.
Cardiorespiratory fitness measured as VO2 max is a stronger predictor of all-cause mortality than body-mass index in large cohorts, which reframes the objective entirely.
Put another way, fitness-tracker energy estimates for anything other than steady-state running are unreliable, often by thirty per cent or more, and treating them as measurements produces systematic overestimation.
Energy-expenditure compensation following exercise interventions is documented in doubly labelled water studies.
Tracker energy figures are estimates with wide error and should not be eaten back.
Fitness predicts outcomes independently of weight, which is reason enough on its own.
The relevant phenomenon is compensation: both behavioural and metabolic, and it erodes a meaningful fraction of the expenditure added.
Compensation is measurable: adding structured exercise typically yields substantially less than the predicted deficit, partly through increased intake and partly through reduced spontaneous movement elsewhere in the day.
Stated carefully, the weight-maintenance literature consistently finds high activity levels — often quoted around sixty minutes of moderate activity daily — among those who sustain a large loss.
Meta-analyses of exercise-only interventions report modest mean weight loss, generally under two kilograms, against much larger effects for dietary interventions.
Nothing here is medical advice.
Diet creates the deficit, exercise protects the composition and the maintenance. Different jobs.
edited 26 Mar 2026 by ruaidhri_o_shea — tightened the wording; no substantive change
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