Study: Calorie restriction equal to exercise

Small study with interesting results.

Improvements in glucose tolerance and insulin action induced by
increasing energy expenditure or decreasing energy intake: a randomized
controlled trial

Am J Clin Nutr. 2006;84:1033-1042.

Background: Weight loss, through calorie restriction or increases in
energy expenditure via exercise, improves glucose tolerance and insulin
action. However, exercise-induced energy expenditure may further
improve glucoregulation through mechanisms independent of weight loss.

Objective: The objective was to assess the hypothesis that weight loss
through exercise-induced energy expenditure improves glucoregulation
and circulating factors involved in insulin action to a greater extent
than does similar weight loss through calorie restriction.

Design: Sedentary men and women aged 50-60 y with a body mass index
(kg/m2) of 23.5-29.9 were randomly assigned to 1 of 2 weight-loss
interventions [12 mo of exercise training (EX group; n = 18) or calorie
restriction (CR group; n = 18)] or to a healthy lifestyle (HL) control
group (n = 10). The insulin sensitivity index and areas under the curve
for glucose and insulin were assessed with an oral-glucose-tolerance
test. Adiponectin and tumor necrosis factor concentrations were
measured in fasting serum. Fat mass was measured by dual-energy X-ray
absorptiometry.

Results: Yearlong energy deficits were not significantly different
between the EX and CR groups, as evidenced by body weight and fat mass
changes. The insulin sensitivity index increased and the glucose and
insulin areas under the curve decreased in the EX and CR groups,
remained unchanged in the HL group, and did not differ significantly
between the EX and CR groups. Marginally significant increases in
adiponectin and decreases in the ratio of tumor necrosis factor to
adiponectin occurred in the EX and CR groups but not in the HL group.

Conclusions: Weight loss induced by exercise training or calorie
restriction improves glucose tolerance and insulin action in nonobese,
healthy, middle-aged men and women. However, it does **not** appear
that exercise training-induced weight loss results in greater
improvements than those that result from calorie restriction alone.