The study: Led by Dr. Edward Weiss, an associate professor of nutrition and dietetics, the team wanted to determine if calorie reduction would lower T3 levels in humans as previous studies had shown it does in rats and mice. To determine if the lowered levels of T3 were a result of calorie restriction and not decreases in fat mass in general, Weiss recruited volunteers to lose weight not only by restricting calories, but also through exercise alone. Study volunteers included sedentary, non-smoking, 50- to 60- year-old men and post-menopausal women with average or slightly above average body mass index values. They were in otherwise good health and did not have cardiovascular disease, diabetes, lung disease, uncontrolled hypertension or evidence of malignancy.
Volunteers were randomly assigned to one of three groups and followed for one year:
--A calorie-restriction group
--An exercise group
--A control group
Volunteers in the calorie restriction group lost weight by reducing their daily calorie intake by 300 to 500 calories per day. Volunteers in the exercise group maintained their regular diet and exercised regularly. Those in the control group made no changes to their lifestyle.
The results: Volunteers in both the calorie-restriction and exercise groups experienced similar changes of body fat mass. However, only volunteers in the calorie restriction group also experienced lower levels of the T3 thyroid hormone. Although a long-term study is still needed to determine if reducing T3 levels through calorie restriction does indeed slow the aging process, Weiss says cutting back on calories is a good idea. "There is plenty of evidence that calorie restriction can reduce your risks for many common diseases including cancer, diabetes and heart disease," Weiss said. "And you may live to be substantially older." When cutting calories, Weiss warns that it is imperative to maintain a healthy diet by eating nutrient-rich foods. What does it mean to cut out 500 calories? It's the equivalent of skipping dessert or eating a turkey sandwich instead of a Big Mac and fries.
But be warned! There are two possible complications:
1. Anorexia nervosa is a condition that is associated with calorie restriction that is far too severe and is accompanied by inadequate intakes of many nutrients. Consequently, it results in premature disease and even death, rather than improvements in health and a slowing of aging.
2. Because it also slows metabolism, calorie-restricted weight loss could make people more prone to weight gain over time. On the other hand, people who lose weight through exercise are not as likely to gain weight back if they quit exercising. The key to maintaining a healthy weight, Weiss says, is keeping a consistent diet and exercising regularly.
The study findings were published in the journal Rejuvenation Research.
