A study, published in Journal of Nutrition, randomly assigned 130 participants to follow a conventional food pyramid weight loss diet or a program known as the Layman's diet.

The Layman's diet, named after study co-author Donald Layman of the University of Illinois at Urbana-Champaign, prescribed approximately 30 percent of all calories from protein. Layman had previously found protein-rich weight-loss diets preserve muscle mass, help lower blood sugar and lipids and improve body composition.

"We substituted lean meats and low-fat milk, cheese, yogurt for some of the high-carbohydrate foods in the food-pyramid diet. Participants also ate five servings of vegetables and two to three servings of fruit each day," research leader Ellen Evans said in a statement.

The study found bone health declined over time in the group that followed the conventional higher-carbohydrate diet.

The researchers said the combination and/or interaction of dietary protein, calcium from dairy and the additional vitamin D in fortified dairy products appears to protect bone health during weight loss.

The research was funded by the Illinois Council on Food and Agricultural Research, the National Cattlemen's Beef Association, the Beef Board, Kraft Foods and the U.S. Department of Agriculture.