Gastric secretion in massive obesity. Evidence for abnormal response to vagal stimulation.

Studies in animals and man suggest involvement of the vagal nerve in the pathophysiology of massive obesity. An abnormal vagal response pattern has been found in the obese rat, but corresponding functional studies in obese man are nonexistent. The gastric acid secretion was therefore examined in 13 nondiabetic grossly obese patients (average body weight 120 kg) and compared to 16 age-matched controls of normal body weight. The gastric acid response to modified sham feeding was significantly (P less than 0.05) reduced in obese patients, being on average 60% of the control output. The obese patients had a higher maximal gastric acid response to graded intravenous pentagastrin, 36.6 +/- 2.9 mmol/hr, compared to 27.1 +/- 2.4 mmol/hr in controls (P less than 0.05). In addition, the patients seemed to need less pentagastrin to reach a secretory plateau. Basal acid secretion rates were similar in obese and control groups. Plasma gastrin and blood glucose were not significantly different in obese patients and controls, but patients had significantly elevated plasma insulin levels. The change of plasma insulin during the sham-feeding procedure correlated with the magnitude of the secretory response in obese and control subjects. The reduced gastric acid response to vagal stimulation in the absence of impaired parietal cell function in obese patients is indicative of an association between massive obesity and altered vagal function in man.