Life style changes improve insulin resistance in hyperinsulinaemic subjects: a one-year intervention study of hypertensives and normotensives in Dalby.

OBJECTIVE

Insulin resistance and hyperinsulinaemia are, in some prospective studies, linked to an increased cardiovascular risk, at least in men. We tested the hypothesis that hyperinsulinaemia may be reduced by non-pharmacological methods independently of other cardiovascular risk factors.

DESIGN

In a non-pharmacological intervention study for 1 year three groups of subjects (hypertensives as well as normotensives) were selected after stratification for insulin level at baseline. Half of the hyperinsulinaemic subjects were randomly assigned to active intervention with physical exercise and dietary regulation (HI-A group), the other half were followed passively during the study period (HI-P group). Normo-insulinaemics and hypo(low)-insulinaemics also underwent active intervention (NI-A and LI-A groups, respectively).

SETTING

Primary health care in Sweden.

RESULTS

During the 1-year follow-up subjects in the HI-A group reduced their weight, waist:hip ratio and systolic and diastolic blood pressure, as well as their low:high-density lipoprotein (LDL:HDL)-cholesterol ratio. Glucose levels before and during an oral glucose tolerance test did not change. However, plasma insulin and plasma-C-peptide decreased both in the fasting state and after 1 and 2 h of oral glucose tolerance testing. This decrease was independent of the previously mentioned reduction in weight, waist:hip ratio, blood pressure and LDL:HDL-cholesterol ratio. No reduction in insulin levels was seen in the HI-P, NI-A or LI-A groups, but in the HI-P group there was a slight decrease in fasting plasma-C-peptide levels. In the HI-A group dietary improvements were observed during the study period, with a reduction in energy intake, fat consumption and cholesterol intake. Fibre intake was increased. No major changes were seen in the HI-P group.

CONCLUSIONS

We conclude that in hypertensive and normotensive subjects with hyperinsulinaemia insulin levels can be reduced by active non-pharmacological treatment for 1 year without altering glucose tolerance. This shows that insulin resistance may be lowered by non-pharmacological treatment, which may be of considerable importance, and not only for hypertensives.