Apr. 5, 2001 CHAMPAIGN, Ill. — New research suggests a diet higher in protein and lower in carbohydrates than currently recommended may help people maintain desirable body weight and overall health.
For 30 years fad diets and various nutritional recommendations have come and gone, said Donald Layman, a professor of nutritional sciences at the University of Illinois. The result: Americans take in more calories than ever, obesity is at an all-time high, and heart disease rates equal those of the 1970s.
In addition, the Centers for Disease Control in Atlanta recently announced a 10 percent rise in the rates of cardiac deaths among 15- to 34-year-olds between 1989 and 1996, and that just 25 percent of Americans over age 18 met basic physical activity recommendations in the 1990s.
"The situation is one of the worst public health fiascos we've ever seen," said Layman, who also is a professor of internal medicine in the UI College of Medicine at Urbana-Champaign. "We may have fewer people dying from heart disease, but that's only because our medical recovery is better. We also are looking at an approaching onslaught of Type 2 diabetes. I think we have a very good reason to re-evaluate where we are at nutritionally."
Layman's research focuses on the relationship between exercise and nutrition, particularly what balance of food helps maintain sufficient muscle mass so a person can efficiently expend energy to maintain a healthy body. Portions of a recent study were to be released in early April during the annual meeting of the Federation of American Societies for Experimental Biology in Orlando, Fla.
For 10 weeks, 24 mid-life women all above ideal weight ate 1,700-calories-a-day diets. One group ate according to the USDA Food Guide Pyramid – 55 percent carbohydrates, 15 percent protein (or 68 grams per day) and 30 percent fat. The experimental group ate a modified daily diet of 40 percent carbohydrates, 30 percent protein (125 grams a day) and 30 percent fat.
The average weight loss of all the women was virtually identical (about 16 pounds). From there, however, there were startling differences for women who ate the higher protein diet. They lost 12.3 pounds of body fat and just 1.7 pounds of muscle mass, a 7-to-1 ratio. Those who stuck to the food pyramid diet lost 10.4 pounds of body fat and, more significantly, 3 pounds of muscle mass – a ratio of 3.5 to 1.
"The protein diet was twice as effective," Layman said. "Women eating the lower protein diet were less capable of burning calories at the end of the study as when they started it. We believe this is the effect of more protein, particularly the increased amount of leucine (an essential amino acid found in protein) in the diet." (Leucine's effect has been documented in several animal studies in Layman's lab).
The study also found higher levels of thyroid hormones among women who ate the protein diet, suggesting a higher rate of metabolism. Protein-eaters also experienced a significant decline of overall triglycerides (fat in the blood) and a slight rise in HDL (the desirable component of cholesterol).
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