Is Vitamin D 25-OH useful for weight loss?

The utility of vitamin D (25-OH) for weight loss is not supported by strong evidence. Observational studies link low vitamin D levels with higher body weight, but randomized controlled trials (RCTs) show no consistent causal effect of supplementation on weight reduction. Vitamin D is essential for bone health and immune function; deficiency may be a marker of obesity rather than a cause. The MyBody-X Nährstoff VitalCheck Basic includes 25-OH vitamin D as a screening marker – useful for detecting deficiency, not for weight loss. High-dose supplementation without medical guidance can be toxic (hypercalcemia). Evidence: human-moderate for association, but not for weight loss intervention. Sources: none specific in provided context. Caveat: commercial tests may overstate benefits.