Brain-Derived Neurotrophic Factor (BDNF)
BDNF is a growth factor in the brain that acts on the hypothalamus to reduce food intake; when its signalling is reduced, appetite rises and weight gain follows.
Plain English
Patient-Friendly Explanation
Brain-derived neurotrophic factor, usually shortened to BDNF, is a protein that helps nerve cells grow, survive and form new connections. It also has a second job that matters for weight: it acts on a part of the brain called the hypothalamus to reduce food intake. BDNF is produced in large amounts in the ventromedial hypothalamus, which is one of the brain regions that controls appetite, and the melanocortin system, which includes the receptor most closely linked to rare inherited obesity, controls how much BDNF is made there. When BDNF signalling is reduced, animals eat more and become obese, and infusing BDNF into the brain of mice that lack the melanocortin 4 receptor reduces their overeating and weight gain. The finding carries over to people. Individuals born with only one working copy of the BDNF gene, and rare families with a mutation in the BDNF receptor, both develop early overeating and obesity, which is why BDNF is considered part of the brain's normal appetite brake. BDNF also acts in the reward circuitry of the brain, where it influences how strongly highly palatable food is wanted. Physical activity raises BDNF, so exercise supports appetite regulation partly through this route. It is not a medicine or a test used in routine weight clinics, but it helps explain why appetite is a brain process rather than a simple matter of willpower.
Medical
Clinical Definition
Brain-derived neurotrophic factor is a neurotrophin that signals through the tropomyosin-related kinase B (TrkB) receptor and is highly expressed in the ventromedial hypothalamus, a key node in energy homeostasis. The melanocortin 4 receptor controls BDNF expression in the ventromedial hypothalamus, and central BDNF infusion attenuates hyperphagia and diet-induced weight gain in MC4R-deficient mice, placing BDNF downstream of the principal central appetite pathway. Global reduction of BDNF signalling causes hyperphagia and obesity in rodents, and in humans BDNF haploinsufficiency is associated with raised food intake and childhood-onset obesity, while a human TrkB mutation that prevents receptor autophosphorylation also produces obesity and hyperphagia. TrkB hypomorphs expressing roughly a quarter of normal full-length receptor are obese, confirming a dose-dependent relationship. In the ventral tegmental area, BDNF and TrkB influence hedonic feeding through the mesolimbic dopamine system, so the factor operates on both homeostatic and reward-driven eating. Energy status regulates BDNF and TrkB expression in the hypothalamus and hindbrain, and physical activity raises circulating BDNF. Measurement is a research tool rather than a clinical test, and no BDNF-directed therapy is approved for obesity.
Key Insight
Why It Matters
BDNF explains a clinically important idea: appetite is regulated by specific brain circuits, and rare single-gene defects in those circuits cause severe early obesity. It sits naturally alongside leptin, ghrelin and the melanocortin pathway in counselling patients, and it gives a biological basis for the appetite-control benefits of regular exercise, which raises BDNF. It is not a routine measurement and no treatment targets it yet.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: October 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
