Altered Postprandial Gastric and Autonomic Functions in Obese Subjects: 2010 Presidential Poster

Purpose: Obesity is an eating disorder but it is unclear whether the responses of gastric and autonomic functions to food ingestion are altered in obese. The aims of this study were to investigate gastric myoelectrical activity (GMA) and autonomic functions in obese subjects and to compare their responses to different meals with lean subjects. Methods: The study was performed in 12 healthy lean and 12 healthy obese subjects. GMA was measured using electrogastrography and autonomic functions were assessed using spectral analysis of heart rate variability derived from the electrocardiogram. The recordings were made in two sessions each composed of a 30-min fasting period and a 30-min period after a fatty soup or protein soup (160cal from fat or protein). Results: 1) The obese showed enhanced responses to both soups. The percentage of normal slow waves was reduced with the fatty soup in lean (73.9±5.3% vs. 59.7±6.0%, P<0.02) but not in obese (68.9±5.1% vs. 67.7±4.8%, P>0.3); The power of gastric slow waves was not altered with the protein soup in the lean but increased in the obese (34.3±2.9 dB vs. 30.8±2.5 dB, P<0.05). 2) Autonomic functions were altered in obese subjects in both fasting and fed states. The obese showed a reduced vagal activity (0.45±0.05 vs. 0.58±0.03, P<0.04), and increased sympathetic activity (0.55±0.05 vs. 0.42±0.03, P<0.04) and sympathovagal balance (1.59±0.27 vs. 0.78±0.10) in the fasting state, and a complete absence of normal postprandial autonomic responses to the test meal. Conclusion: The findings on gastric slow waves demonstrate that obese subjects are more receptive to fatty meals and more responsive to protein meals. Obese subjects have impaired autonomic functions in both fasting and fed states. The alterations in gastric and autonomic functions may contribute to eating disorders in obese subjects.