Protein-rich diet boosts benefit of exercise

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Protein-rich diet boosts benefit of exercise

http://www.medicalnewstoday.com/medicalnews.php?newsid=29723

29 Aug 2005

Everyone knows that a good weight-loss program combines diet and

exercise, but a new University of Illinois study reports that

exercise is much more effective when it's coupled with a protein-rich

diet.

" There's an additive, interactive effect when a protein-rich diet is

combined with exercise. The two work together to correct body

composition; dieters lose more weight, and they lose fat, not

muscle, " said Layman, a U of I professor of food science and

human nutrition.

A higher-carbohydrate, lower-protein diet based on the USDA food

guide pyramid actually reduced the effectiveness of exercise, Layman

said.

Forty-eight adult women participated in Layman's 4-month study,

published in the August 2005 issue of the Journal of Nutrition. One

group ate a protein-rich diet designed to contain specific levels of

leucine, one of the essential amino acids. A second group consumed a

diet based on the food guide pyramid, which contained higher amounts

of carbohydrates.

Both groups consumed the same number of calories, but the first group

substituted high-quality protein foods, such as meats, dairy, eggs,

and nuts, for foods high in carbohydrates, such as breads, rice,

cereal, pasta, and potatoes.

" Both diets work because, when you restrict calories, you lose

weight. But the people on the higher-protein diet lost more weight.

Some people refer to this as the metabolic advantage of a protein-

rich diet, " said Layman.

The study included two levels of exercise. " For one group, we

recommended that they add walking to their lives. They usually walked

two to three times a week, less than 100 minutes of added exercise, "

the researcher said.

The other group was required to engage in five 30-minute walking

sessions and two 30-minute weightlifting sessions per week. In both

groups of dieters, the required exercise program helped spare lean

muscle tissue and target fat loss. But, in the protein-rich, high-

exercise group, Layman noted a statistically significant effect. That

group lost even more weight, and almost 100 percent of the weight

loss was fat, Layman said. In the high-carbohydrate, high-exercise

group, as much as 25 to 30 percent of the weight lost was muscle.

While this protein-rich diet works for everyone, it seems to be even

more effective for people who have high triglyceride levels and carry

excess weight in their midsection--a combination of health problems

known as Syndrome X.

" The protein-rich diet dramatically lowered triglycerides and had a

statistically significant effect on trunk fat, both risk factors

associated with heart disease, " he said. " Exercise helped dieters

lose an even greater percentage of body fat from the abdominal area. "

The protein-rich diet works so well because it contains a high level

of the amino acid leucine. Leucine, working together with insulin,

helps stimulate protein synthesis in muscle. " The diet works because

the extra protein reduces muscle loss while the low-carbohydrate

component gives you low insulin, allowing you to burn fat, " he said.

" We believe a diet based on the food guide pyramid actually does not

provide enough leucine for adults to maintain healthy muscles. The

average American diet contains 4 or 5 grams of leucine, but to get

the metabolic effects we're seeing, you need 9 or 10 grams, " he

noted.

To achieve that leucine level, the researcher recommended adding

dairy, meat, and eggs, all high-quality proteins, to the diet.

According to Layman, losing weight doesn't have to mean relying on

supplements to fill in nutritional gaps in your diet. " If you use a

high-quality protein approach to your diet, you can actually improve

the overall quality of your diet while losing weight, " he said.

Other researchers involved in the study are Ellen , I.

Baum, Seyler, Donna J. kson, and A. Boileau, all

of the University of Illinois. The study was funded by the Illinois

Council on Food and Agricultural Research (C-FAR), the National

Cattlemen's Beef Association, the Beef Board, and Kraft Foods.