Impedance change during intentional weight loss in Thai obese patients

Abstract

Background & aims: Longitudinal measurements of raw bioelectrical impedance analysis (BIA) parameters suggested a worsening of the nutritional status in obese patients during weight loss after bariatric surgery. The effects of weight reduction through dietary intervention on raw BIA parameters is rarely described. Methods: A retrospective observational study was conducted on obese patients who were in a weight-loss program. Dietary counseling, exercise, and lifestyle modification were suggested as the main approach to lose weight. Then longitudinal follow-up visits were scheduled every 1–3 months for up to 2 years. On each visit, body weight, waist, and hip circumferences were recorded along with BIA measurements. Repeated measures correlation (rrm) was used to assess the relationship between BIA-derived impedance and body weight. Results: A total of 116 obese patients were recruited. Participants had lost their weight from 113.47 ± 26.73 kg at the first visit to 103.69 ± 23.97 kg at the last visit (P < 0.001). A significant decrease of percentage of body fat was observed by −3.30 ± 4.33% from baseline. Total body water and fat-free mass were also significantly decreased. There was an increase in impedance from 483.55 ± 78.38 ohm at baseline to 496.11 ± 82.30 ohm at the last visit (P < 0.001). The rrm between impedance and body weight was −0.31 (95% CI −0.37 to −0.25, P < 0.001). Conclusions: Impedance had a significant negative correlation on body weight in obese patients during intentional weight loss, which might be due to decreased total body water and fat-free mass. Further study is required to explore the clinical meaning of these changes.