June 25, 2012 (Houston, Texas) — Although diet alone and in combination with exercise improves insulin sensitivity and other cardiometabolic risk factors in older obese adults, exercise alone shows no similar benefits, according to research presented here at ENDO 2012: the Endocrine Society 94th Annual Meeting.
The 1-year trial included 107 obese adults with an average age of about 70 years and an average body mass index of 37 who were randomly assigned to either a control group, a group that was managed with diet alone, a group that was managed with exercise alone, or a group that was managed with a combination of diet and exercise.
There were no significant differences between any of the groups at baseline in terms of cardiovascular disease or medications.
The diet group receive instructions to reduce caloric intake by about 500 to 700 calories per day. The patients were weighed weekly; they were also instructed to include 1 gram of high-quality protein per kilogram of body weight and to take a multivitamin with calcium.
Ninety-three participants (87%) completed the trial. The results showed that the insulin sensitivity index, measured using an oral glucose tolerance test, improved in 70% of participants in the diet group and in 86% of those in the diet plus exercise group, but improvements were not seen in the exercise only or control groups (P < .05 between groups).
Improvements were seen in the glucose and insulin area under the curves during the oral glucose tolerance test for the diet group (10%) and the diet plus exercise group (15% to 20%), but again, not in the exercise or control groups (P < .05 between groups).
The trend was consistent across a variety of cardiometabolic measures, with the diet and diet plus exercise groups showing decreases in systolic blood pressure (-9% and -10%, respectively ), diastolic blood pressure (-8% and -6%), waist circumference (-7% and -7%), abdominal visceral fat ( -25% and -33%), serum triglycerides (-26% and -27%), C-reactive protein (-27% and -27%), and tumor necrosis factor receptor (-7% and -9%), and an increase in adiponectin (21% and 33%).
None of the improvements were seen in the exercise only group or the control group.
In the diet group, body weight was decreased by about 10%, and in the diet plus exercise group, body weight loss was 9%, but there was no decrease in body weight in the exercise or control groups (P < .05 between groups).
One notable aspect of the improvements was that at the initial 6-month follow-up, the improvements in the combination of exercise and weight loss group were not yet apparent, said lead author Matthew Bouchonville, MD, assistant professor in the Department of Internal Medicine at the University of New Mexico, in Albuquerque.
"At 6 months, the diet and diet plus exercise groups looked the same, so it didn't appear that there was an effect from the exercise, and if we'd only looked at 6 months, we could have concluded that the inclusion of exercise did not help improve insulin sensitivity. However, after following them for 12 months, we actually did see a continued improvement of about 70% above baseline insulin sensitivity, which was not seen in the diet group during the weight maintenance period of the study," he said.
"So this is a novel finding in this population and suggests a distinct complementary effect of exercise, but only in the setting of prerequisite weight loss."
Although the adverse health effects of obesity are well known, there is debate over the appropriate treatment approach for older adults.
In a study recently published in the New England Journal of Medicine, the authors reported that a combination of weight loss and exercise provided greater improvement in physical function than either intervention alone for older adults.
The new study underscores the fact that those benefits extend to insulin sensitivity, Dr. Bouchonville said.
"Whereas at baseline there was no significant between-group difference, there were differences at 6 and 12 months. This was driven by a reduction in the prevalence of metabolic syndrome in the diet intervention and the diet plus exercise groups, in which cases we saw a reduction of greater than 50% in metabolic syndrome prevalence."
"This lends support to the recommendation of lifestyle interventions directed at this population that incorporate both diet-induced weight loss as well as exercise," Dr. Bouchonville concluded.
Dr. Bouchonville has disclosed no relevant financial relationships.
ENDO 2012: The Endocrine Society 94th Annual Meeting. Abstract #S18-1. Presented June 23, 2012.
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