Spot Reduction: What One New Study Found
For decades, the fitness consensus has been that you cannot choose where your body loses fat. A 2023 randomized controlled trial published in Physiological Reports challenges that, at least in one narrow case. It matters because it reframes a question most people have asked about their own waistline: does ab work actually shrink the belly, or just strengthen what's underneath it.
The setup: matched effort, different targets
Researchers led by Mathias Forsberg Brobakken and colleagues recruited 16 overweight men and split them into two groups for ten weeks. One group ran on a treadmill. The other did the same running plus torso rotations and abdominal crunches, with total training energy expenditure matched between groups so neither side simply worked harder overall.
This design matters: it means any difference in outcomes can't be explained by one group just burning more calories. The only real variable was where the extra exercise volume was aimed.
What moved, and what didn't
Using DEXA scans, the researchers found trunk fat mass dropped significantly more in the ab-exercise group, 1170 grams (7 percent), compared to no measurable change in the running-only group. That's a between-group difference of 697 grams, or about 3 percent.
But total body fat and body weight fell by similar amounts in both groups. In other words, the ab-focused group didn't lose more fat overall, they appear to have lost it from a different place. The ab group also got noticeably stronger, with torso rotation strength up 39 percent and crunch strength up 36 percent, well ahead of the control group's gains.
Read this as a question, not an answer
Sixteen men is a small sample, and the intervention group trained roughly twice the volume of exercises targeting the trunk. That alone could account for part of the effect. This single result also sits against a much larger body of meta-analytic research that has consistently found no spot-reduction effect.
The honest read: this is a provocative outlier, not a settled finding. It's worth watching for replication in larger, more diverse samples before anyone treats it as a training rule.
What this means for your own numbers
If you're tracking your own body with Trainr, this study is a useful reminder of what to actually watch for. A single scan can't tell you whether crunches are reshaping your waist. A trend line, built from the same measurements taken consistently, can start to show whether your waist, chest, or arm measurements are moving independently of your overall body-fat estimate.
That's the real value of longitudinal tracking: it separates what you're hoping happened from what your numbers show did happen. Trainr builds a 3D scan from two phone photos and tracks waist, chest, arms, and an estimated body-fat trend over time, estimates, not diagnoses, but consistent ones you can compare month to month. The first scan is free.
Scan yourself — the first one is freeOne study hints your waist might listen to targeted work, but your trend line is still the only honest judge.
Trainr is a wellness tool, not a medical device. Measurements and body-composition figures are estimates for self-tracking; for medical questions, talk to a professional.