The studies, presented at the Experimental Biology 2004
meeting in Washington, showed that short, simple workouts could
have significant effects if done consistently.A team at Baylor University in Texas reported on studies that looked at 160 overweight and sedentary women.
They took part in a commercial health and weight loss program known as Curves, which encourages 30-minute workouts three days a week and also a low-calorie diet plentiful in protein and certain vegetables.
"We found it to be highly effective in promoting weight loss with no adverse side effects, especially among participants who followed the high-protein, low-carb, low-fat diet," said Richard Kreider, an exercise expert who led the study.
The women in the study did the workouts for 14 weeks, Kreider told the conference on Wednesday.
"Following 10 weeks of dieting and exercising to lose weight and raise their metabolic rate, study participants were able to eat as much as 2,600 calories a day and maintain their weight loss," Kreider said.
"These women also lost fat, increased the proportion of muscle to body weight, gained strength, and made medically significant improvements in blood pressure, resting heart rate and aerobic fitness."
A Canadian team tested a different, home-based resistance program on middle-aged and elderly volunteers and found they got not only stronger muscles, but also a stronger immune system.
Jennifer DiPenta, Dr. Julia Green-Johnson and colleagues at Acadia University in Nova Scotia studied 10 men and 12 women aged 54 to 82.
The participants followed a 30-minute, three-day-a-week schedule but used stretchy tubes and resistance balls at home to work their muscles for 11 months.
Blood tests showed their bodies produced higher levels of natural killer cells, one line of defense against infection. They did not lose weight on the program but lowered their cholesterol, DiPenta told the conference on Monday.
The sustained exercise may be the key, they said, because earlier studies using shorter periods of up to three months did not find such marked changes.
"It was gratifying to see the improvement in these older people in ways that should enable them to maintain their health and independence with advancing age," Green-Johnson said.