Aims: To examine the effect of weight loss on insulin sensitivity and beta-cell function in severely obese subjects of varying glycaemic control.
Patients and methods: Subjects were 254 (F:M 209:45) patients having adjustable gastric banding for severe obesity, with paired biochemical data from before operation and at 1-year follow up. The homeostatic model assessment method was used to calculate insulin sensitivity (HOMA%S) and beta-cell function (HOMA%B). Subjects were grouped by diabetic status and by pre-weight loss HbA1c.
Results: Initial mean (sd) weight and body mass index were 128 (26) kg and 46.2 (7.7) kg/m2, respectively, and at 1-year were 101 (22) kg and 36.4 (6.7) kg/m2. The percentage of excess weight lost (%EWL) was 44.3 (14)%. HOMA%S improved from 37.5 (16)% presurgery to 62 (25)% (P < 0.001). %EWL was the only predictor of HOMA%S improvement (r = 0.28, P < 0.001). Subjects with normal fasting glucose, impaired fasting glucose and Type 2 diabetes had a fall, no change and increase in HOMA%B, respectively. The improvement in HOMA%B in subjects with diabetes (n = 39) was inversely related to the time with diabetes (r = -0.36, P = 0.02). In non-diabetic subjects the HOMA%S-HOMA%B relationship was favourably altered with weight loss, so that for any given HOMA%S there was an increase in HOMA%B (f = 11.8, P = 0.001). This improvement in HOMA%B was positively related to %EWL (r = 0.25, P = 0.019).
Discussion: There are beneficial changes in both insulin sensitivity and beta-cell function with weight loss. Modern laparoscopic obesity surgery may have an important early role in the management of Type 2 diabetes in obese subjects.