Background

Body Mass Index (BMI) as a measure of overall health faces ongoing scrutiny, without established alternative measures. This study investigated whether defining obesity based on body fat percentage (BF%) could offer a more comprehensive identification of persistent obesity post-bariatric surgery.

Methods

This retrospective, single-center analysis focused on patients undergoing Laparoscopic Roux-en-Y gastric bypass or sleeve gastrectomy. Bioimpedance analysis (BIA) data, encompassing BF%, fat mass (FM), and fat-free mass (FFM), were collected pre- and post-operatively (baseline to 1-4 years). Inclusion criteria: age >= 20 years, >= 1 BIA collection >=1 year post-operatively. Exclusion criteriaRevisional bariatric surgery. Persistent obesity was defined as BMI >=30 kg/m2 or BF% >=30% for women or >=25% for men.

Results

Of the 7471 and 937 patients meeting inclusion criteria, 63% exhibited persistent obesity based on BMI at year 1 post-surgery, while 92% showed persistent obesity by BF%. This continued at years 2 and 3, with 59% and 65% experiencing persistent obesity based on BMI, respectively, compared to 90% and 94% using BF% (Table 1). FFM gradually declined over the entire follow-up period, while FM reached nadir at 20 months post-surgery, with a subsequent increase correlating with weight and BF% recurrence (Figure 1). Women experienced a greater rate of decline (12.5%) in FFM than men (3.7%) in the first 12 months (p<0.0001, Figure 1).

Conclusions

BMI underestimates the occurrence of obesity compared to body fat percentage. Weight regain following bariatric surgery primarily correlates with an increase in fat mass.