IMPORTANCE OF GLUCAGON AS A DETERMINANT OF RESTING METABOLIC-RATE AND GLUCOSE-INDUCED THERMOGENESIS IN OBESE WOMEN

The long-term results of dietary treatment for obesity are often very poor. To predict the effect of a hypocaloric diet, it may be important to consider factors that could influence energy expenditure, especially those altered in obesity. Elevated plasma levels of glucagon are associated with obesity. In this study, the relationship of glucagon to resting metabolic rate (RMR) and glucose-induced thermogenesis (GIT) has been investigated. RMR and GIT, after ingesting 100 g glucose, were measured by indirect calorimetry in 25 obese premenopausal women (body mass index [BMI], 37.2 ± 4.7 kg · m-2). RMR was significantly related to fat-free mass (FFM) (r = .50, P < .005). A significant relation could be found between RMR and fasting glucagon levels (r = .36, P < .05). Plasma glucose and insulin levels were not predictive for RMR. Mean GIT increased with increasing waist-hip circumference ratio (WHR) (r = .71, P < 0.0001), confirming previous findings of our group. No relation was found between GIT and glucagon levels, neither in the basal state nor after glucose. The only important metabolic determinant was area under the curve (AUC) for glucose (r = .45, P < .01), suggesting a higher GIT in obese women with impaired glucose intolerance. This suggests that the control of energy metabolism by the concentration of glucagon may be more important in the fasting state than after a meal. Plasma glucagon concentration should be considered in the evaluation of RMR. © 1991.