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Keywords:

  • cardiovascular risk factors;
  • diet;
  • exercise;
  • glucose;
  • insulin

Objectives. To compare the single and joint effect of 1-year diet and exercise intervention on carbohydrate metabolism and associated coronary risk variables.

Design. Unmasked, randomized, 2×2 factorial intervention trial with 1-year duration for each participant.

Setting. The participants were recruited from a screening examination of 40-year-old persons in Oslo, Norway.

Subjects. Two hundred and nineteen sedentary men and women, with diastolic blood pressure 86–99 mmHg, HDL cholesterol <1.20 mmol L-1, triglycerides >1.4 mmol L-1, total cholesterol 5.20–7.74 mmol L-1 and BMI>24. Participants were randomly allocated to control (n=43), diet (n= 55), exercise (n=54) and diet+exercise (n=67).

Interventions. Exercise: supervised endurance exercise three times a week. Diet: reduce weight, increase the intake of fish and reduce total fat intake.

Main outcome measures. One-year changes in insulin and glucose before and after a standardized glucose load.

Results. As compared with controls fasting insulin in pmol L-1 decreased significantly in the combined diet and exercise group (3.9±6.2 versus -22.6±4.7 respectively, P=0.003). Insulin in pmol L-1 after glucose load decreased significantly in all intervention groups compared to controls (diet: -82.2± 49.9 P=0.02; exercise: -92.4±60.1 P=0.03; diet+exercise: -179.6±45.1 P=0.0004). Fasting glucose in mmol L-1 decreased significantly in the diet alone group (0.21±0.07 P=0.006) and in the diet+exercise group (-0.26±0.08 P=0.005). In a subgroup analysis of the good responders, the observed changes with respect to total cholesterol (-0.76 mmol L-1), HDL cholesterol (0.16 mmol L-1), triglycerides (-0.72 mmol L-1), systolic and diastolic blood pressure (-8.5/-6.8 mmHg) were all statistically significant compared to the control with P<0.001.

Conclusions. Exercise and diet intervention and in particular the combination of the two, were effective in improving carbohydrate metabolism. Associated risk factors were also affected in a beneficial direction.