, Volume 48, Issue 7, pp 1258-1263
Date: 04 Jun 2005

The effect of insulin on cardiac autonomic balance predicts weight reduction after gastric bypass

Abstract

Aims/hypothesis

The aim of this study was to assess the predictive role of autonomic reactivity in body weight loss induced by gastric bypass.

Methods

A group of 22 morbidly obese subjects, who were due to undergo a gastric bypass, were submitted, before surgery, to a euglycaemic–hyperinsulinaemic clamp, during which a continuous recording of the ECG was performed. The effect of insulin on cardiac autonomic balance was evaluated by performing power spectral analysis of heart rate variability. The low-to-high frequency ratio was calculated before and during the clamp and its modifications were expressed as % delta low-to-high frequency ratio (%Δ L: H).

Results

Preoperative %Δ L: H showed a significant (p=0.0009, r 2=0.43), positive relationship to the reduction of body weight, measured 1 year after surgery and expressed as % excess weight loss (% EWL). Preoperative BMI was also significantly (p=0.0009, r 2=0.43) negatively related to the 12-month % EWL. In a multiple regression analysis, %Δ L: H remained a significant (p=0.003), independent predictor of body weight loss, even when preoperative BMI or age, % fat mass, insulinaemia and glucose disposal were taken into account.

Conclusions/interpretation

The best correction of excess body weight was achieved by those obese subjects who had a preserved capacity to shift their cardiac autonomic balance towards a sympathetic prevalence in response to an euglycaemic–hyperinsulinaemic clamp. Further studies are needed to elucidate the mechanisms through which the autonomic nervous system influences weight reduction.