Morning or evening workouts: a small edge for evening, and a lot of caveats
A meta-analysis of randomised trials in the Journal of Health, Population and Nutrition compared morning and evening exercise programmes. Both changed body composition. Evening showed modestly larger changes, but the authors say the evidence can't support firm advice.
Soma Labs2 min read
People who exercise often ask whether the time of day matters. A meta-analysis published on October 28 in the Journal of Health, Population and Nutrition pulled together randomised trials to look at one part of that question: body composition.
What was pooled
The authors, Sayevand, Khoshnoudi, Faraji Safar, Moradi, Zokaei, Karimy, Naghavi and Azizi, searched for randomised clinical trials published up to July 2026. They included trials in adults aged 18 or older that compared people exercising in the morning, people exercising in the evening, and, where available, control groups who didn't follow the programme.
They then combined the results for weight, body mass index, fat mass, fat percentage and lean tissue.
What the numbers showed
Both morning and evening exercise reduced weight, body mass index and fat mass compared with the control groups. That part is consistent with what most people would expect.
When morning and evening were compared directly, evening came out a little ahead. On the standardised measures the authors used, evening training went with larger reductions in weight (a standardised difference of 0.77), fat mass (0.58) and lean tissue (0.20). Fat percentage was 0.35 percentage points lower with evening training.
Note that last point. Evening training also went with a slightly larger drop in lean tissue, not only fat.
Why the authors hold back
The authors describe the evening advantage as modest, and they are clear that it doesn't add up to a recommendation.
They give three reasons. The trials differed a lot from one another, which shows up as high heterogeneity in the pooled results. The trials relied on bioelectrical impedance to measure body composition, rather than more precise body scans. And the trials controlled diet unevenly, so differences in eating could explain part of the gap.
The authors call for larger, standardised trials using more precise body composition scans and biomarker checks.
What it doesn't say
It doesn't say morning exercise is worse, or that anyone should move their workouts. Both timings changed body composition. The difference between them was small, and the evidence behind it is uneven.
Where Soma fits
The lesson we take is about measurement. When the instrument, the time of day and the conditions vary from one session to the next, small differences become hard to trust. That is true across a meta-analysis, and it is true for one person tracking themselves.
Soma is a general wellness product, not a medical device. It doesn't diagnose anything, and it doesn't measure fat mass or body composition. Soma Axon, the pod we are still building, uses the same light, cameras and stance every week, and shows each value with its margin of error, so a change over time is easier to trust. We wrote more about that in The same instrument, every week.
Sources, as of October 29, 2026: Sayevand, Khoshnoudi, Faraji Safar et al., Journal of Health, Population and Nutrition. This post describes research and isn't medical advice.