A high-protein diet is tied to a higher metabolism, including 45% more storage of lean tissue, when compared with a low-protein diet, but that metabolism increase is not sustained after switching to a normal-protein diet, researchers reported at Obesity Week 2014.
Study author Elizabeth Frost, PhD candidate, Pennington Biomedical Research Center, Baton Rouge, Louisiana, said the findings suggest that the human body cannot be trained to maintain a higher metabolism by simply eating a high-protein diet.
Rather than conducting a weight-loss study, Frost and her colleagues focused on whether high-protein or low-protein diets might lead to less weight gain when consuming excess calories due to the ability of the body to burn extra energy as a result of the high-protein diet.
The researchers found that the study participants all gained similar amounts of weight, regardless of diet composition. However, there was a vast difference in how the body stored the excess calories. Those who consumed normal-protein and high-protein diets stored 45% of the excess calories as lean tissue or muscle mass, whereas those who on the low-protein diet stored 95% of the excess calories as fat.
The study was a randomized, controlled overfeeding trial of 16 healthy participants with varied amounts of protein (low, 5%; normal, 15%; and high, 25%) for 8 weeks while living in a metabolic ward. Diet-induced thermogenesis (DIT) — one of three components of energy expenditure — was measured over 4 hours by indirect calorimetry following meals.
Results showed that the area under the curve (AUC) for energy expenditure after overfeeding breakfast was significantly associated with grams of protein (P=.02), with AUC being significantly increased in the high-protein vs. low-protein diet groups (P=.05). Nevertheless, data also indicated that DIT in response to the normal-protein meal was not linked to prolonged exposure to high-protein intake (P=.16).
The researchers concluded that DIT is under acute regulation and is not involved in adaptive thermogenesis.
One mechanism for weight loss success with high-protein diets, like the Atkins Diet or the Ideal Protein Diet, could be due to an increase in the body’s natural process of metabolizing food for energy following meals, the researchers noted.
Steven R. Smith, MD, President of The Obesity Society, said in a press release that high-protein diets for weight loss or to build muscle mass can certainly be effective. However, he said this study suggests the diet composition must be maintained for dieters to continue to see and sustain results.
Adam Tsai, MD, who specializes in Internal Medicine at University of Colorado Hospital in Denver, said the study is rather unusual. Instead of putting the subjects on diets or restricting their intake, all of these subjects were overfed, he said, and this study may raise more questions than it answers.
“One important thing is that they are overeating. They are taking in more than their normal requirement and so you have to wonder how applicable it is to dieting and people trying to lose weight,” Dr. Tsai in an interview with Endocrinology Advisor.
- Frost E et al. Abstract T-3127-OR. Presented at: Obesity Week 2014; Nov. 2-7, 2014; Boston.