Summary: In 195 adults with obesity, an 8-week low-calorie diet was followed by a comparable rise in serum 25-hydroxyvitamin D in both women (+12 nmol/L, 95% CI 9-15) and men (+13 nmol/L, 95% CI 8-17; P < .001 for both). A sex difference emerged only during 52 weeks of weight-loss maintenance: a further increase in 25(OH)D accompanied continued weight loss in women (+14 nmol/L, 95% CI 6-22; P = .001) but not in men, and lower baseline vitamin D tracked with successful maintenance in women alone.
PICO Summary
| Element | Detail |
|---|---|
| Population | 195 adults with obesity (BMI 32-43 kg/m2), Denmark; secondary analysis of a 52-week placebo-controlled weight-loss-maintenance RCT (NCT04122716). |
| Intervention | 8-week low-calorie-diet weight loss, then 52-week maintenance with liraglutide, exercise, or both. Exposure of interest: degree of weight loss/regain and sex. |
| Comparison | Within-person baseline versus post-diet values; women with further weight loss versus women regaining weight; women versus men. |
| Outcome | Serum 25(OH)D rose after the low-calorie diet in women (+12 nmol/L, 95% CI 9-15) and men (+13 nmol/L, 95% CI 8-17), P < .001 for both. At week 52, women with further weight loss gained +14 nmol/L (95% CI 6-22; P = .001) versus women regaining weight; no such effect in men. Women maintaining weight loss had lower baseline 25(OH)D (54 nmol/L, SD 19) than women regaining (70 nmol/L, SD 25; P < .001). No NNT or ARR reported (continuous outcome, secondary analysis). |
Expert Commentary
The verdict is that this is a credible, well-powered secondary analysis whose central message is narrower than its title may suggest. Diet-induced weight loss raised serum 25(OH)D similarly in both sexes, so the headline finding is shared, not female-specific. What differed was the maintenance phase, where continued weight loss and a low baseline vitamin D level were associated with rising 25(OH)D and successful maintenance in women but not men. The principal limitation is that these sex-specific signals derive from non-randomised comparisons within a trial designed for a different primary endpoint; weight regain was not allocated, so confounding and reverse causation cannot be excluded and the findings should be read as hypothesis-generating rather than confirmed. Can I use this with my patients? Not yet as a reason to alter vitamin D management, though it reasonably reinforces measuring 25(OH)D in women with obesity entering a structured weight-loss programme and watching how it tracks with adherence. Readers should note the parent trial involved liraglutide and that several authors are affiliated with a foundation-funded metabolic research centre, which warrants the usual caution. Future work should test prospectively whether low baseline vitamin D genuinely predicts maintenance, and whether the sex difference reflects fat-mass redistribution or a true metabolic divergence.
References
Holt R, Holt J, Jorsal MJ, Sandsdal RM, Jensen SBK, Byberg S, et al. Weight Loss Induces Changes in Vitamin D Status in Women With Obesity But Not in Men: A Randomized Clinical Trial. J Clin Endocrinol Metab. 2025;110(8):2215-2224. doi:10.1210/clinem/dgae775
