Independent and additive effects of energy restriction and exercise on glucose and insulin concentrations in sedentary overweight men.
BACKGROUND
Overweight and inactivity are associated with impaired glucose tolerance, reduced insulin sensitivity, and diabetes. Few controlled trials have assessed the independent and combined effects of energy restriction and exercise on the prevention of these conditions.


OBJECTIVE
The objective was to evaluate the independent and additive effects of 16 wk of energy restriction and exercise on glucose and insulin concentrations.


METHODS
Sixty nonsmoking, overweight, sedentary men aged 20-50 y were randomly assigned to either maintain or restrict their energy intake (4186-6279 kJ/d). Within each of these arms, the subjects were further randomly assigned to either a light-intensity (control) or a vigorous-intensity exercise program for 30 min 3 times/wk.


RESULTS
Fifty-one subjects completed the study. Maximal oxygen uptake increased ( approximately 24%; P < 0.001) with vigorous but not with light exercise. Significant weight loss was observed with energy restriction (x: 10.12 kg; 95% CI: 8.02, 12.22 kg; P < 0.001) but not with exercise. Vigorous exercise reduced fasting glucose and glucose and insulin areas under the curve (AUCs) by 13% (P = 0.01) and 20% (P = 0.02), respectively. Exercise effects were independent of weight change. Energy restriction resulted in a 40% reduction in the insulin AUC (P = 0.01). Vigorous exercise and energy restriction were additive in reducing the insulin AUC.


CONCLUSIONS
Energy restriction and vigorous exercise independently and additively reduce glucose and insulin concentrations in response to an oral-glucose-tolerance test. Both of these lifestyle interventions provide a potent strategy that should be an integral part of any program to reduce the risk of impaired glucose tolerance, insulin resistance, and diabetes in overweight and sedentary persons.
School of Medicine and Pharmacology, University of Western Australia, Royal Perth Hospital, PO Box x2213, GPO Perth, Western Australia 6847, Australia. kaycox@cyllene.uwa.edu.au
Kay L
KL
Cox
Valerie
V
Burke
Alan R
AR
Morton
Lawrence J
LJ
Beilin
Ian B
IB
Puddey
D000328:Adult; D001786:Blood Glucose; D015992:Body Mass Index; D004032:Diet; D002149:Energy Intake; D015444:Exercise; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000628:therapy*; D010809:Physical Fitness
D001786:Blood Glucose; D007328:Insulin