B12 supplementation is given to people with demonstrated or likely B12 deficiency
The strongest published finding is from the foundational Biochemical Pharmacology study by Neelakantan et al.: in diet-induced obese mice, daily 5-Amino-1MQ administration produced reductions in body weight, white adipose tissue mass, and adipocyte size without any significant change in food intake
Many people are also genetically predisposed to having impaired B12 absorption
Furthermore, certain medications, such as some laxatives and drugs used to treat tuberculosis, can also cause this effect
Who Tends to Be B12 Deficient
It is caused by the caloric restriction and rapid weight loss, which trigger a shift of hair follicles from the growth phase to the resting and shedding phase