Purdue UniversityIndividuals who are overweight usually prefer diets that are rich in proteins. However experts from the Purdue University reveal that postmenopausal women consuming diets based on higher protein intake need to be alert of lower bone density. Scientists examined information gathered from two controlled diet analyses.

In the first analysis they lowered daily diets by 750 calories in order to attain one-and-one-half-pound weight loss every week for a period of 12 weeks. Participants enlisted for the study were aged between 43 and 80. Among these women, fifteen received meat-free diets with protein from vegetarian, diary and egg sources. This intake comprised 18 percent of every woman’s energy intake. This intake however was compared to the suggested dietary allowance of 0.36 grams of protein per pound of body weight each day.

Wayne W. Campbell, professor of foods and nutrition shares, “We know that when overweight, postmenopausal women reduce their energy intake to successfully lose weight, they can lose less lean body mass when they consume higher amounts of protein and include lean meats, such as pork loins, ham, beef and chicken, in their diet. However, we also found that these older women lost bone mineral density faster than women who consumed normal protein diets that did not contain any meats. This finding is of concern for this age group that is susceptible to osteoporosis.”

The diets for other 13 women consisted 30 percent of energy from protein whereas 40 percent of the protein was consumed from lean pork, namely loin and ham and 60 percent of protein was consumed from vegetarian, diary and egg sources. Experts observed that women on an average lost 19 pounds, however those consuming diets rich in protein and meat lost bone mineral density.

Campbell reveals, “Purposeful, moderate weight loss is an effective way for overweight postmenopausal women to improve their health and well-being. However, research shows that older women are at risk of losing bone when they lose weight, and our findings highlight that amount and sources of protein are important to consider when choosing a weight-loss diet. Each individual needs to evaluate, or consult with a dietitian about how to achieve and sustain a healthy body weight and body composition, including muscle and bone.”

The second analysis included 43 postmenopausal women who consumed a 1,250 calorie diet for a period of nine weeks. All participants enlisted for the analysis consumed the same 1000 calorie vegetarian diet. However 15 women received 250 calories from chicken breast meat, 14 women consumed 250 calories from beef tenderloin and another 14 women consumed 250 calories from short bread cookies and sugar coated chocolates. The other 11 women formed the control group. Experts observed the same findings that women lost weight but lost bone mineral density as compared to the control group.

Campbell elucidates, “The impact of dietary protein on bone remains controversial, and information about dietary protein and bone from studies with weight-stable subjects might not be applicable to weight loss. We know that bone is constantly forming and breaking down, and how fast these two processes occur determines the density of your bones. We don’t have the data at this time to know the mechanisms involved with these changes in bone density. It is also important to note that these two studies were relatively short, nine to 12 weeks, so studies to evaluate how protein intakes impact body composition and bone beyond the period of active weight loss would be helpful.”

Experts measured the bone mineral density with the help of a dual-energy X-ray absorptiometer. They however feel that additional analysis is required to understand how various amounts and sources of protein affect the bone when people lose weight.

The findings are published online in the Journal of Gerontology: Medical Sciences and will be printed in September.