BDNF levels in individuals with obesity and anxiety and/or depression symptoms who participated in a weight loss program

Abstract

Introduction. Depression, anxiety and obesity are highly prevalent conditions in Mexico with shared pathophysiological mechanisms. Regular physical exercise has been shown to be an effective non-pharmacological intervention in their treatment, due in part to Brain-Derived Neurotrophic Factor (BDNF), a protein secreted by contracting skeletal muscle and involved in neuroplasticity, cognition and mood regulation. Several studies have shown reduced serum levels of BDNF in people with obesity, anxiety or depression. However, it is not yet known how these levels are modulated under an exercise and diet program in individuals with these three conditions simultaneously. Objective. To quantify serum BDNF levels in obese individuals with and without symptoms of depression and anxiety before and after a 3-month weight-loss program (WLP) based on exercise and a low-calorie diet. Methodology. Blood samples were taken from 77 individuals diagnosed with obesity (BMI ≥ 30 kg/m²) after signing an informed consent form (INR 114/24), and data on body composition and symptoms of depression and anxiety were collected. Body composition was analyzed using bioelectrical impedance, and symptoms of depression and anxiety were assessed using the Beck Depression Inventory (BDI) and Anxiety Inventory (BAI). Based on the cut-off points of the BDI (≥10) and the BAI (≥6), the following groups were formed: the control group with obesity without symptoms of anxiety and depression before Cpre (n=54) and after Cpost (n=54) of the intervention and the group with symptoms before the WLP(Spre) (n=22), which was further subdivided according to persistence (S1post) (n=4) or improvement (S2post) (n=18) of symptoms after the intervention. Serum BDNF levels were determined by ELISA before and after the WLP. Statistical analysis included the Kolmogorov-Smirnov test for normality and Student's t-test, with a p-value ＜0.05 considered significant. Results. At the end of the WLP, all groups showed improvements in body composition (p < 0.001). BDNF levels did not change significantly in any of the groups. The group with symptoms of depression and/or anxiety before the WLP (Spre) had the lowest BDNF levels. Nevertheless, neither the persistence (S1post) nor the improvement (S2post) of symptoms was associated with significant changes in BDNF levels. Conclusions. The WLP improved body composition in individuals with obesity, but no significant changes in serum BDNF levels were observed, even in individuals with improvement in emotional symptoms.