Blunted glucose-induced thermogenesis: a factor contributing to relapse of obesity.

It is well established that the long-term effect of weight-reducing diet therapies is disappointing, since the majority of those overweight regain their previous body weight regardless of the procedure used to maintain weight reduction. Glucose-Induced-Thermogenesis (GIT) was shown to be diminished in 55 obese patients particularly in the presence of insulin resistance (r = 0.44 p < 0.001) and in obese diabetic patients (3.7 +/- 0.7% vs 8.6 +/- 0.9% p < 0.001). After weight loss the combined effect of a decreased basal energy expenditure and an attenuation of GIT resulted in a postprandial energy expenditure which was markedly lower than in the overweight state (1.48 +/- 0.10 Kcal/min vs 1.15 +/- 0.05 Kcal/min p < 0.01). With six years evolution of obesity, GIT decreased significantly in non-diabetic obese (6.8 +/- 1.1% before and 4.1 +/- 0.8% after 6 years evolution p < 0.05) and was still blunted in the diabetic group (3.1 +/- 0.8% before and 2.1 +/- 0.7% after). The decrease in GIT was accompanied by reduction in glucose tolerance and insulin response. In conclusion, the decrease in GIT after weight loss and after six-years evolution of obesity, which accompanies the worsening of glucose tolerance and occurrence of diabetes, is a mechanism which may contribute to maintain the obese state by a reduction of energy expenditure.