Can B12 help with weight loss?

Vitamin B12 is essential for energy metabolism and red blood cell formation. A deficiency can cause fatigue and low energy, which might indirectly reduce physical activity and calorie expenditure. However, there is no strong scientific evidence that B12 supplementation alone leads to significant weight loss in people with normal B12 levels. Most claims are based on marketing or weak mechanistic reasoning. Even in deficiency, weight loss is not a primary outcome; rather, correcting deficiency improves overall vitality. For individuals without deficiency, taking B12 is unlikely to cause weight loss. A balanced diet and calorie control remain the key factors for weight management. Caution: High doses are generally safe but unnecessary. Evidence level: mechanistic/mixed; no robust clinical trials support weight loss claims.