Anthropometric and Body Composition Changes After Bariatric Surgery—The Effect of Sex, Age, and Type of Surgery

The rise in obesity and its associated health problems increases the need for therapeutic approaches such as bariatric surgery. Therefore, this study aims to explore the changes in the anthropometric and body composition characteristics of patients undergoing bariatric surgery. A retrospective longitudinal study was conducted in subjects ≥ 18 y who underwent bariatric surgery and attended one nutrition appointment before and after surgery. Information on their sex, age, weight, fat mass (kg and %), fat-free mass (kg and %), and skeletal muscle mass, obtained using bioelectrical impedance, and on their waist circumferences was collected. Their BMIs and skeletal muscle mass indexes were calculated. The differences in the anthropometric and body composition parameters between pre- and post-surgery were also calculated. The participants were grouped by sex, age groups (18–44 y and 45–69), and type of surgery (Roux-en-Y gastric bypass and gastric sleeve). The variables are presented as n (%) and as means (SDs) or medians (interquartile ranges). Student’s t-test and the Mann–Whitney test were employed (p < 0.05). The sample consisted of 57 subjects (aged 18–69 years; 75% women). Between the pre- and post-surgical periods (63 (42) days), their weight (mean: 103.0 (SD: 16.3) kg vs. 91.2 (14.2) kg, p < 0.001); BMIs (37.9 (4.2) kg/m2 vs. 33.6 (4.1) kg/m2, p < 0.001); waist circumferences (116.2 (12.4) cm vs. 105.7 (12.3) cm, p < 0.001); % fat mass (45.5 (6.0) vs. 41.0 (8.0), p < 0.001); skeletal muscle mass (32.8 (7.4) kg vs. 30.3 (6.5) kg, p < 0.001); and skeletal muscle mass indexes (12.0 (1.8) kg/m2 vs. 11.1 (1.7) kg/m2, p < 0.001) decreased; meanwhile, their % fat-free mass increased (54.7 (6.0) vs. 59.0 (8.0), p < 0.001). Most of these changes occurred regardless of sex, age, or type of surgery. Shortly after bariatric surgery, patients show a better nutritional status and body composition.