When University of Colorado at Boulder researchers came out with a study in 1998 showing older adults who exercise regularly burn more calories at rest than their sedentary counterparts, it was good news for the active older generation.
Now comes some not so good news.
A new CU-Boulder study has shown that active older adults who slowed down their physical activity showed significant drops in their resting metabolism in less than a week, even though they had reduced their caloric intake accordingly. Such a metabolic slowdown can set the stage for weight gain and associated problems like increased risks for cardiovascular disease and other metabolic diseases like diabetes, said postdoctoral researcher Christopher Bell.
"This is further evidence of the importance of exercise for older people," said Bell of CU-Boulder's department of kinesiology and applied physiology who headed up the study. "Declines in the resting metabolic rate increase the challenge of weight maintenance and most likely contribute to the high prevalence of age-associated obesity and higher incidences of related diseases."
Bell presented a paper on the findings at the Experimental Biology Meeting held in Orlando in early April. Co-authors on the study included CU graduate student Danielle Day, CU postdoctoral researcher Demetra Christou, Colorado State University researcher Kris Osterberg, CSU Professor Christopher Melby and CU-Boulder Professors Douglas Seals and Pamela Jones.
For the study, the researchers monitored seven healthy male and three healthy female adults between 62 and 67 years of age who exercised regularly and had less than 25 percent body fat. The researchers restricted the subjects' exercise by the equivalent of 400 calories a day and restricted their caloric intake by roughly the same amount.
In less than a week, the resting metabolic rate declined significantly, from an average of 1,248 calories on day one to 1,155 calories on day five.
"Older people who grow sedentary must continually restrict their caloric intake in order to maintain healthy weight, a change that eventually may limit their ability to achieve recommended daily allowances of vitamins and nutrients," said Bell.
Studies on active and inactive young adults in their 20s and 30s show much smaller differences in metabolic rate, said Bell. Although CU-Boulder researchers have not studied the effects of regular exercise and caloric intake on metabolic rate in active and sedentary adults in their 40s and 50s, Bell predicted the metabolic differences would fall somewhere in the middle between older and younger study subjects.
"In a word, the message is exercise," said Bell. "It is important at any age to exercise and eat nutritious foods in order to stay healthy."