Background Lifestyle intervention is effective in the prevention of type 2 diabetes in individuals with impaired glucose tolerance (IGT). It is currently unknown whether it has beneficial effects on metabolism to a similar extent, in individuals with normal glucose tolerance (NGT) compared to individuals with IGT.
Materials and methods Data from 181 subjects (133 with NGT and at risk for type 2 diabetes and 48 with IGT) who participated in the Tuebingen Lifestyle Intervention Program with increase in physical activity and decrease in caloric intake were included into this study. Body fat distribution was quantified by whole-body magnetic resonance (MR) tomography and liver fat and intramyocellular fat by 1H-MR spectroscopy. Insulin sensitivity was estimated from an oral glucose tolerance test (OGTT).
Results After 9 ± 2 months of follow-up, the diagnosis of IGT was reversed in 24 out of 48 individuals. Only 14 out of 133 participants with NGT developed IGT. Body weight decreased in both groups by 3% (both P < 0·0001). Two-hour glucose concentrations during an OGTT decreased in individuals with IGT (–14%, P < 0·0001) but not with NGT (+2%, P = 0·66). Insulin sensitivity increased both in individuals with IGT (+9%, P = 0·04) and NGT (+17%, P < 0·0001). Visceral fat (–8%, P = 0·006), liver fat (–28%, P < 0·0001) and intramyocellular fat (–15%, P = 0·006) decreased in participants with IGT. In participants with NGT these changes were significant for visceral fat (–16%, P < 0·0001) and liver fat (–35%, P < 0·0001).
Conclusions Moderate weight loss under a lifestyle intervention with reduction in total, visceral and ectopic fat and increase in insulin sensitivity improves glucose tolerance in individuals with IGT but not with NGT. In individuals with NGT, the beneficial effects of a lifestyle intervention on fat distribution and insulin sensitivity possibly prevent future deterioration in glucose tolerance.