Can Folsäure help with weight loss?

Folic acid (vitamin B9) is essential for one-carbon metabolism and DNA synthesis, and some mechanistic research suggests it may influence lipid metabolism and energy balance. However, there is no robust human evidence that folic acid supplementation directly causes weight loss. Observational studies show mixed associations between folate status and body weight, but these are confounded by diet and lifestyle. Randomized controlled trials have not demonstrated a significant effect of folic acid on weight reduction in generally healthy populations. The evidence is primarily mechanistic (cell/animal studies) and does not support using folic acid as a weight-loss aid. In individuals with a confirmed deficiency, correcting folate levels may improve metabolic health, but the impact on weight is modest at best. Over-the-counter folic acid is safe within recommended doses (400–800 µg/day), but high doses can mask B12 deficiency. Direct-to-consumer genetic tests that claim to personalize folic acid intake for weight loss are largely marketing-driven; the effect of common MTHFR variants on weight is small and not clinically actionable. For sustainable weight loss, focus on diet, exercise, and behavioral changes rather than single supplements.