CONTEXT: Brain-derived neurotrophic factor (BDNF) is a neurotrophin important for neuronal survival and synaptic plasticity that also plays a role in metabolic regulation (energy homeostasis and appetite control). Lower circulating BDNF levels have been associated with obesity, metabolic risk factors, and poorer cognitive and mental health outcomes, whereas higher levels are linked to more favorable profiles.
OBJECTIVE: In this study we sought to systematically evaluate the effects of dietary weight-loss interventions on circulating BDNF levels in adults with overweight or obesity.
DATA SOURCES: A comprehensive literature search of PubMed, Web of Science, Scopus, and Google Scholar was conducted from inception through April 2025 to identify clinical trials investigating dietary weight-loss or calorie-restriction interventions in adults with overweight or obesity that reported data regarding circulating BDNF outcomes.
DATA EXTRACTION: Eligible studies were clinical trials with interventions lasting ≥4 weeks to investigate circulating BDNF concentrations before and after dietary interventions that were conducted in adults (≥18 years old) with baseline overweight or obesity.
DATA ANALYSIS: This systematic review was conducted in accordance with Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 guidelines. Risk of bias was assessed using the Cochrane risk-of-bias tool. Data on study design, participant characteristics, dietary interventions, and BDNF outcomes were extracted and synthesized qualitatively. A summary table of the included studies was generated.
RESULTS: Fifteen clinical studies (n = 862 total participants) met inclusion criteria (11 randomized trials and 4 single-arm trials). Diet modalities included continuous calorie restriction (typically 20%-30% caloric deficit), intermittent fasting (eg, alternate-day fasting, time-restricted eating), ketogenic diets (KDs), Mediterranean-type diets, and other weight-loss diets. Duration of interventions ranged from 6 to 26 weeks. Responses to BDNF varied by intervention. In adults with overweight/obesity, weight-loss dietary interventions demonstrated heterogeneous effects on circulating BDNF. We categorized the included studies into 3 groups based on the effects of dietary weight loss on BDNF: increases, no significant change, or decreases. Approximately half of the studies showed no significant effect, while a few interventions showed a decrease. Intermittent fasting regimens and certain dietary patterns (eg, the Mediterranean-DASH [Dietary Approaches to Stop Hypertension] [MIND] diet, and the KD) tend to elevate BDNF levels, whereas continuous calorie restriction often shows no change, and very rapid weight loss may paradoxically reduce BDNF in some cases.
CONCLUSIONS: These findings suggest that diet-induced weight loss can influence neurotrophic status, potentially modulating brain health. However, results are inconsistent across studies. Overall, interventions involving intermittent calorie restriction, MIND, and/or KD, more frequently reported BDNF increases, whereas continuous calorie restriction produced mixed results.
