Malnutrition in its many forms remains a world-wide epidemic. In the United States, more than 60 percent of adults are classified as overweight or obese, whereas third-world nations are struggling with under-nutrition and insufficient food supplies. A new study provides scientific insight that may benefit development of public health policy to influence healthy weight gain.
The study, published January 4 in the Journal of the American Medical Association (JAMA), examines the impact of diets containing varying amounts of protein on weight gain, body composition, and energy expenditure. The research, led by Sanford-Burnham’s Steven R. Smith, M.D. and George Bray, M.D., Pennington Biomedical Research Center, found that total calories account for increases in body fat, while increasing the percent of dietary protein during overfeeding led to more lean body mass storage. This work appears to be the first to analyze the impact of dietary protein during overfeeding and provides guidance on dietary composition for healthy weight gain.
Consuming a high protein/low calorie diet for weight loss has been a well-known, yet controversial method of dieting. Protein in the diet may raise resting energy expenditure, effectively burning calories. The study’s investigators were intrigued by this principle and decided to look at the impact of varying levels of protein during overconsumption to better understand metabolic changes that occur during obesity.
“A large number of studies have been performed to understand the role of protein to help dieters. Our work addresses the possibility that protein is important to help prevent weight gain through increased calorie burning,” explained Dr. Smith, scientific director of the Florida Hospital – Sanford-Burnham Translational Research Institute for Metabolism and Diabetes (TRI).
Participants lived in an inpatient unit for 10 to 12 weeks. Initially, test subjects consumed a weight stabilizing diet while their energy expenditure was measured. Subsequently, they were fed diets with 40 percent higher energy value with either five percent (low), 15 percent (normal), or 25 percent (high) of calories from protein. Body composition was measured biweekly using a whole body scanner. Body fat increased similarly in all three protein diets. Resting energy expenditure and body protein increased significantly with the normal and high protein diets. While the low protein diet resulted in less total weight gain, all of the weight was deposited as fat. In contrast, weight gain on the mid- and high-level protein diets included increased lean body mass.
The study is remarkable for its duration and number of participants, having evaluated 25 participants for 24 hours per day during a 10-week inpatient period. The authors believe that this is the first study to analyze the impact of three levels of dietary protein during overfeeding and one of a few to calculate both resting and total energy expenditure.
“As obesity develops, metabolic changes occur that reflect the differences in the way that individuals process food. The next phase of research will evaluate the mechanisms that account for the increased energy burned,” said Dr. Smith. “Understanding how the body increases calorie burning will provide insight into novel ways to rev up metabolism as a way to treat metabolic diseases, such as obesity, diabetes, and cardiovascular diseases.”
Orlando’s soon-to-open TRI, a collaboration between Sanford-Burnham and Florida Hospital, will enable this kind of cutting-edge clinical research in metabolism. The new facility will house clinic space, testing rooms, a 3T MRI scanner, a DEXA scan, calorimetry rooms to measure energy metabolism, and a biorepository. These and other technologies will help researchers understand the metabolic origins of obesity and diabetes. The TRI is expected to open in early 2012.
Bray, G., Smith, S., de Jonge, L., Xie, H., Rood, J., Martin, C., Most, M., Brock, C., Mancuso, S., & Redman, L. (2012). Effect of Dietary Protein Content on Weight Gain, Energy Expenditure, and Body Composition During Overeating: A Randomized Controlled Trial JAMA: The Journal of the American Medical Association, 307 (1), 47-55 DOI: 10.1001/jama.2011.1918