Protein-Rich Diets and Weight Loss
New research explains for the first time how and why a moderately
high protein diet may be the best for losing weight. The new findings
suggest that eating more high quality protein will increase the
amount
of leucine, an amino acid, in the diet, helping a person maintain
muscle mass and reduce body fat during weight loss. Maintaining
muscle during weight loss efforts is essential because it helps the
body
burn more calories.
The findings of two related papers involving diets of increased
protein and reduced carbohydrates appear in the February issue
of the Journal
of Nutrition. The research was led by Donald K. Layman, Professor
of Nutrition in the Department of Food Science & Human Nutrition
at the University of Illinois at Urbana-Champaign.
Dr. Donald K. Layman, a Professor in the College of Medicine, tested
his hypothesis on 224 mid-life, overweight women who consumed diets
of 1,700 calories a day for 10 weeks. Physical activity of the participants
was held constant.
The control group ate according to the USDA Food Guide Pyramid. They
consumed approximately 0.36 grams of protein and 1.3 grams of carbohydrates
per pound of body weight per day. Study group participants increased
the amount of protein they ate daily to about 0.73 grams per pound
of body weight. And they reduced their intake of carbohydrates to
0.95 grams per pound of body weight.They also built their diets around
high
quality proteins, which provided the optimal level of leucine to
improve body composition. Leucine has been shown to be a regulator
of muscle,
which is important to maintain when losing weight. While the body
makes many other amino acids, it does not produce leucine. Leucine
is found
primarily in high quality protein foods such as beef, dairy products,
poultry, fish and eggs.
Dr. Layman cautions that it is a mistake to think about dietary protein
as a percent of calories. “What is important about my plan,” he
said, “is that protein needs are based on body weight and not
on a percent of the calories consumed.”
The study group’s daily diet consisted of 9 to 10 ounces of meat,
including at least seven beef meals per week, three servings of low-fat
milk or cheese and a minimum of five servings of vegetables. They also
included two servings of fruit and four servings of grains, pasta and
rice. The study group ate in accordance with the National Cholesterol
Education Program’s Step 1 heart-healthy guidelines.
Most of the public debate about diet continues to focus on the extremes
of very high (Atkins’ Plan) or very low (Ornish Plan) levels
of proteins. Dr. Layman’s plan falls within the protein range
recently recommended by the National Academy of Sciences Food and
Nutrition Board. The USDA Food Guide Pyramid falls at the low end
of the accepted
protein range.
In Dr. Layman’s study, both diet groups lost a similar amount
of weight about 16 pounds, but the study group lost more body fat
and less muscle mass than the control group. Those who followed the
moderately
high protein diet lost two pounds more of body fat, yet maintained
one pound more muscle mass than the control group.
The study challenges the conventional wisdom about the role of low-fat
foods in weight loss. Layman said, “Traditionally, people have
built a diet around low-fat foods, instead of high quality protein
foods. Study participants following the moderately high protein plan,
which I call the ‘Sensible Solution’ were twice as effective
in maintaining lean muscle mass,” he said. “Muscle helps
burn calories, but is often compromised during weight loss.”
Nutrition experts have long debated the virtues of many of the high
protein diets because of conventional concerns related to the consumption
of saturated fat and cholesterol. However, Layman said, the opposite
was true in his study. “The group following my diet lost fat,
maintained muscle and had an improvement in total blood cholesterol
level. Subjects found the eating plan easy to follow, allowing them
to enjoy foods from all food groups.”
Source: Condensed from a press release written by Jim Barlow, Life
Science Editor, University of Illinois 2/10/03
Spring 2003
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