EFFECTS ON GLUCOSE-TOLERANCE, INSULIN-SECRETION, INSULIN-LIKE GROWTH-FACTOR-1 AND ITS BINDING-PROTEIN, IGFBP-1, IN A RANDOMIZED CONTROLLED DIET AND EXERCISE STUDY IN HEALTHY, MIDDLE-AGED MEN

Objectives. To study the effects of advice on diet, exercise and their combination on oral glucose tolerance (OGTT), insulin secretion, insulin-like growth factor-1 (IGF-1) and its binding protein, IGFBP-1. Design. A 6-month, randomized, controlled intervention study. Setting. Primary health care centres in Sollentuna, Stockholm and the Department of Medicine, Karolinska Hospital, Stockholm, Sweden. Subjects. One hundred and fifty-seven normoglycaemic healthy men, mean age 46 years, range 35-60 years, with slightly to moderately raised cardiovascular risk factors. Interventions. Advice on diet (D, n = 40), exercise (E, n = 39) a combination of both (DE, n = 39) and a control group (C, n = 39), Main outcome measures. An OGTT, insulin secretion, IGF-1 and its binding protein, IGFBP-1. Results. The number of pathological OGTTs in the intervention groups decreased from 42/118 to 33/118 whilst the number in the control group did not change. Easting insulin levels decreased in groups E and DE from 8.8-7.4 mU L(-1) (P < 0.01) and from 8.3-6.7 mU L(-1) (P < 0.01), respectively. Accordingly, the insulin area under the curve decreased from 5278 to 4828 (P < 0.05) in group E, and from 5482 to 4809 (P < 0.01) in group DE. IGF-1 only increased in group D. The most prominent changes were noted for IGEBP-1, which increased in all three intervention groups and to the highest degree in group DE (from 33.7-42.6 mu g L(-1), P < 0.001). Conclusions. A combination of increased exercise and improved diet, as well as increased exercise alone, favourably affect glucose and insulin homeostasis in middle-aged men with moderately elevated cardiovascular risk factors. The most marked changes were noted for IGFBP-1, possibly suggesting a decreased insulin secretion and an enhanced insulin sensitivity.