For obese seniors, dieting and exercise together are more effective at improving physical performance and reducing frailty than either alone.
The research, by a team at Washington University School of Medicine in St. Louis, is reported March 31 in The New England Journal of Medicine.
Older adults who are obese face severe health risks, including high blood pressure, heart disease and diabetes, which can be compounded by a lack of mobility.
"We wanted to tease apart the effects of dieting and exercise in older people who are obese," says principal investigator Dennis T. Villareal, MD, adjunct associate professor of medicine at Washington University School of Medicine in St. Louis. "In older adults, obesity exacerbates declines in physical performance and leads to frailty, impaired quality of life and increases in nursing home admissions. Given the increasing prevalence of obesity even among older people, it is important to find ways to combat the problem and help seniors remain healthier and more independent."
In this study, Villareal and his colleagues evaluated the effects of dieting and exercise in more than 100 obese seniors over a one-year period. Although weight loss alone and exercise alone improved physical function by about 12 percent and 15 percent, respectively, neither was as effective as diet and exercise together, which improved physical performance by 21 percent.
The investigators used the Physical Performance Test, a test that evaluates an individual's ability to perform tasks, such as walking 50 feet, putting on and removing a coat, standing up from a chair, picking up a penny, climbing a flight of stairs and lifting a book.
In addition, the researchers evaluated peak oxygen consumption during exertion with treadmill walking. On that test, obese elderly people who both dieted and exercised improved 17 percent from their baseline. The diet-only group showed a 10 percent gain, and the exercise-only group improved about 8 percent.
All subjects in the study were over 65, with some as old as 85 when the study began. Their average age was about 70. Volunteers were randomly assigned to one of four groups. One set of seniors was placed on a low-calorie diet to help them lose weight. Members of a second group attended exercise sessions three times a week, doing balance work, resistance training and aerobic exercise. A third group combined both the low-calorie diet and the exercise. The last group made no changes in diet or exercise habits.
All subjects had medically significant obesity, defined as having a body mass index (BMI) of 30 or more. BMI measures the relationship between a person's height and weight.
At the study's outset, participants had evidence of frailty and impaired physical function based on their Physical Performance Test and on measures of their peak aerobic capacity using an exercise stress test and a questionnaire about their physical function.
Villareal and his team also surveyed study subjects about their quality of life, and again, those in the combined diet-exercise group had the biggest improvements. Their scores improved by 15 percent, compared to 14 percent in the diet-only group and 10 percent in the exercise-only group. By every measure, strength, balance and gait all showed the most consistent improvement in the diet-exercise group.