Evidence check: B12 in the context of weight loss

Vitamin B12 is often marketed for weight loss, especially as an energy booster. However, scientific evidence is weak: in non-deficient individuals, B12 supplementation does not lead to significant weight loss. B12 is essential for energy metabolism, but extra intake does not increase basal metabolic rate. Some studies show an association between low B12 levels and obesity, but causality is unclear – obesity may cause low B12 due to poor diet rather than vice versa. Most claims are based on marketing or mechanistic reasoning. Caveat: B12 deficiency should be diagnosed and treated by a physician, but self-supplementation for weight loss is not evidence-based.