Evidence check: B12 in the context of Abnehmen

The claim that vitamin B12 directly promotes weight loss is poorly supported by evidence. B12 is essential for energy metabolism and red blood cell formation, but deficiency is rare in the general population – except in vegans, older adults, or those with absorption issues (e.g., after gastric bypass, Crohn's disease, or metformin use). In such cases, supplementation can correct fatigue and anemia, indirectly supporting physical activity and calorie expenditure. However, randomized controlled trials show no significant weight loss from B12 in non-deficient individuals. Many commercial 'metabolism boosters' rely on questionable lab tests (e.g., hair analysis) rather than clinically validated serum levels. The evidence for a weight-reducing effect is best rated as 'marketing' or 'unclear'. Routine B12 testing for weight loss is not recommended by professional guidelines. A balanced diet and medical evaluation for suspected deficiency are more appropriate.