High-protein diet linked with sustained weight loss

By Joene Hendry

NEW YORK (Reuters Health) - Middle-aged women who followed a high-protein diet compared with those who followed a low-protein diet lost more weight over a 1-year study period, according to researchers from Australia.

"Whether this was actually due to the protein per se or the fact that those women best able to restrict calories chose high protein foods, is not known," lead investigator Dr. Peter M. Clifton of Adelaide University told Reuters Health.

Regardless of protein levels, Clifton added, "even small amounts of weight loss at 12 months were associated with considerable benefits in terms of lipids."

Overall, the women who lost weight had a 20-percent increase in high-density lipoprotein (HDL), the "good" cholesterol, report Clifton and colleagues at CSIRO Human Nutrition.

The researchers assessed the long-term impact of a high-protein diet on weight loss and weight maintenance in 72 obese but otherwise healthy women, an average of 49 years old. They began with an intensive 12-week weight loss diet, and continued on a similar diet for an additional 52 weeks.

The two diets were high-protein -- 34 percent of calories from protein - or high carbohydrate diet -- 64 percent from carbohydrates. Fat provided 20 percent of the calories in both diets, the investigators report in the American Journal of Clinical Nutrition.

After calculating protein levels from the diet records the participants kept over the entire 64-week study period, the researchers found those consuming the highest amount of protein per day averaged 6.5 kilograms (14.3 pounds) of weight loss. By contrast, women consuming the lowest amounts of protein averaged 3.4 kilograms (7.5 pounds) of weight loss.

However, compliance with the diets was poor over time. So, the researchers further examined dietary protein levels, weight and lipid levels in the group as a whole. They found that protein was still directly related to weight loss, but not with improved blood lipid values.

A higher protein diet appears to confer some weight loss benefit, the researchers conclude, while sustained weight loss provides health benefits, whether the diet is high-protein or high-carbohydrate.

SOURCE: The American Journal of Clinical Nutrition, January 2008.