Slashing the number of calories rats consume throughout life is proving to avert age-related loss of brain function. It's well-known that life-long calorie restriction--the laboratory equivalent of fasting--dramatically prolongs life in laboratory animals. In this study, the brain cells of inactive old rats responded to specific chemical signals like those of young rats when they were served only 63 percent of the calories they would normally have eaten. Normally, the receptors for these chemicals, called muscarinic receptors, decline in mid-life. This leads to a loss of memory and some motor functions dependent on these receptors. But in the calorie-restricted rats, these receptors functioned 25 percent better than in a control group that got all the food they wanted. The finding is in line with studies by others showing that calorie restriction throughout life spares dopamine receptors, which control movement and decline dramatically with aging.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
James A. Joseph, (617) 556-3178

Women over 50 would benefit from visiting the gym regularly to strengthen thigh and torso muscles, and thus prevent osteoporosis and related fractures. A year-long study of women aged 50 to 70 shows that strength training can preserve bone density and prevent losses in muscle strength, balance and physical activity. Such losses lead to falls--the greatest risk factor for fractures in the elderly. Twenty of the 39 volunteers strengthened muscles in the abdomen, the upper and lower back, the front and back of thighs and the buttocks on pneumatic equipment for just 40 minutes twice a week. Meanwhile, a control group of 19 women continued their normal lifestyle. At the end of the year, the trained group had gained one percent more bone density at the hip and spine compared to a 2.5 percent loss in the control group. They also increased strength in the trained muscles ranging from about 35 to 76 percent above the control group. Their balance improved 14 percent. And their spontaneous physical activity--excluding the training sessions--increased by an average 27 percent, whereas it decreased in the control group by nearly as much. The researchers are now testing the effectiveness of comparable exercises they developed that can be done at home with simple, low-cost leg weights and dumbbells.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Miriam E. Nelson, (617) 556-3094

As people age, they lose the automatic ability to regulate appetite and weight, according to a study of both young and older men. The findings help to explain two trends: People tend to gain weight and double body fat during middle age, then lose weight and body mass after age 65. These trends contribute to middle-age obesity and elderly malnutition. In the study, nine older men kept on the extra pounds gained during three weeks of eating about 1,000 calories more than their normal intake each day. Ten young men, however, automatically ate less and dropped back to their normal weight over the following six weeks. In fact, much of the weight-loss occurred during the first 10 days after overeating, even though all volunteers were instructed to eat normally and not try to lose weight. Older men don't bounce back from undereating, either. After three weeks of eating about 800 calories less than usual, they didn't automatically increase their intake. The young men gained back more than they lost in the six-week follow-up despite the request to eat normally. The findings are the first direct evidence of an age-related loss of appetite control.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Susan Roberts, (617) 556-3237

A high-intensity strength training program can be an effective way for older people to maintain their weight while eating more. And it can reduce body fat, according to a study of 12 men and women in their late 50s, 60s and 70s. The volunteers lived at a USDA center during the three-month study so researchers could account for all of the calories they consumed, as well as measure how many calories they burned. Three times a week, the volunteers exercised muscles in the upper leg, upper torso and arms at 80 percent of the maximum weight each could lift at a given session. After 12 weeks, they were eating an average 15 percent more calories just to maintain their starting weight, while losing an average four pounds of body fat. One-third of those extra calories were burned during the resistance exercises themselves. Another one-third were needed to fuel an increase in the people's resting metabolic rate--the energy needed to keep the leaner body functioning while at rest. The research demonstrates the benefits of resistance training in helping older people balance calories burned with calories consumed while losing body fat and maintaining strength for daily activities.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA
Wayne W. Campbell, (814) 865-3453, now at the Noll Physiological Research Center, Pennsylvania State University, University Park, PA

Last Updated: December 13, 1996
Return to: Quarterly Report Table of Contents