The antiviral immune defense may be adversely influenced by weight loss through a calorie restriction program in obese women.

Background: Obesity and weight loss are reported to be associated with immune function. This study aimed to investigate the changes in counts of lymphocytes involved in microbial defense during weight loss in obese women. Methods: This clinical trial involved 29 women with a body mass index (BMI) ≥ 30 kg/m2. The intervention group was prescribed a low-calorie diet (600 kcal lower than caloric requirement per day) plus Orlistat (120 mg three times daily). The control group received ad libitum diet. Anthropometric indices, obesity-related traits, and blood pressure were assessed every three weeks. Metabolic indices and plasma count of lymphocyte subpopulations (CD3, CD4, CD8, CD19, and CD16/56, as well as the ratio of CD4:CD8) were measured at baseline and after the intervention (after 10% weight loss). Results: After the weight loss, natural killer cells (CD16/56) decreased in the intervention group (P=0.014) even after adapting for all confounders. No significant changes were observed in other immune markers compared to the control group. Conclusions: Caloric restriction-induced weight loss might independently weaken the antiviral immune defense. Further clinical trials are warranted to better clarify the association between weight loss, calorie restriction, and immunity.