Obese older adults can reduce their chance of developing the metabolic syndrome by losing weight through dieting alone, but adding exercise to a weight loss program has even more benefit, a new study finds. The results, to be presented Saturday at The Endocrine Society's 94th Annual Meeting in Houston, show that a combination of diet-induced weight loss and frequent exercise almost doubled the improvement in insulin sensitivity compared with dieting alone.
The metabolic syndrome is a cluster of metabolic problems that raise the risk of Type 2 diabetes and heart disease: abdominal obesity as shown by a large waist circumference, disturbed lipids (low HDL or "good" cholesterol and high triglycerides), high blood pressure and high blood glucose (blood sugar). Although it is known that weight loss can reduce these risk factors, the most appropriate lifestyle treatment for obesity in older adults has been controversial, said the presenting author, Matthew Bouchonville, MD.
"It was not clear from prior studies in obese elderly adults whether the beneficial effects of diet and exercise are distinct from each other or have additive effects," said Bouchonville, an assistant professor at the University of Mexico Health Sciences Center and the New Mexico Veterans Affairs (VA) Health Care System in Albuquerque.
The researchers investigated the independent and combined effects of diet-induced weight loss and regular exercise in a one-year randomized controlled clinical trial, funded by the National Institute on Aging. They randomly assigned 107 obese adults ages 65 and older to one of four groups: weight management using a calorie-restricted diet, exercise (three times a week for 90 minutes each) without dieting, combined dieting with exercise, and controls (no diet or exercise).
The primary outcome analyzed was the degree of change in the insulin sensitivity index. Insulin sensitivity is the body's ability to successfully clear glucose from the bloodstream and is often impaired in obese people. This index was measured from the oral glucose tolerance test, a blood test for diabetes after the patient drinks a sugary drink.
Other measures obtained included those for the components of the metabolic syndrome as well as C-reactive protein, a measure of inflammation. Research has linked chronic inflammation to diabetes and heart disease.