Calories, Not Protein, Count in Fat Gain

Medpage link

By Kristina Fiore, Staff Writer, MedPage Today Published: January 03, 2012 Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner

Eating too much guarantees that your body will pack on the fat, regardless of how much protein you consume, researchers found. Patients who ate a low-protein diet gained less weight overall than those who ate a normal- or high-protein diet, but they all experienced a similar increase in fat mass when they overate by about 1,000 calories a day, George Bray, MD, of Pennington Biomedical Research Center in Baton Rouge, La., and colleagues reported in the Jan. 4 issue of the Journal of the American Medical Association. "Fat storage was exactly the same with all three levels of protein," Bray told The JAMA Report. "Protein, on the other hand, had no effect on storage of fat, but it did affect weight gain." Some work has suggested that eating a diet high or low in protein could maintain body weight through its potential effects on metabolism; eating too little could spare lean body mass while eating too much could add lean body mass. Action Points   This study found that eating too much guarantees that your body will pack on the fat, regardless of how much protein you consume. All patients gained weight in the study, but those in the low-protein group gained less than those who ate normal or high levels of protein. So Bray and colleagues assessed 25 patients -- 16 males, 9 females -- ages 18 to 35 with a body mass index (BMI) between 19 and 30 who lived in-clinic for the duration of the study. They first had a weight-stabilizing diet, followed by randomization to diets consisting of 5%, 15%, or 25% energy from protein. During this phase, patients overate for eight weeks, increasing their overall energy intake by about 40%, or an additional 954 kcal per day. Bray and colleagues found that all patients gained weight, but those in the low-protein group gained less than those who ate normal or high levels of protein (3.16 kg versus 6.05 kg and 6.51 kg, respectively, P=0.002). Yet those in the low-protein group gained less lean body mass than those in the normal or high protein groups (0.7 kg versus 2.87 kg and 3.18 kg, P<0.001), largely accounting for the differences in weight gain. And the overall increase in fat mass was similar between groups, rising about 3.51 kg from baseline, they reported. They also found that resting and total energy expenditure rose among those who had normal- or high-protein diets, but it didn't change in the low-protein group. Lona Sandon, MEd, RD, of the University of Texas Southwestern Medical Center, who was not involved in the study, said in an email to MedPage Today and ABC News that the findings "confirm what other research has confirmed -- calories count" when it comes to obesity. "A low-protein diet may mean you weigh less, but might cause higher levels of body fat," Sandon said. "Those that ate the low-protein diet gained less weight overall, but the weight they gained was mostly body fat. Excess body fat is related to metabolic syndrome and other health issues even if you are of normal or slightly overweight." Sandon also noted that the increased gain in muscle mass among those on the normal- and high-protein diets likely accounts for the increase in resting energy expenditure. "We also know from other research that protein has a higher thermic effect on food," he said in the email. "Higher protein intake requires more calories to digest, absorb, and metabolize compared to carbohydrate or fat. This may partly explain the increased calorie expenditure in the normal-to-high-protein groups." Bray cautioned that the study was limited because the majority of patients were male and black, and the findings may lack generalizability, but still concluded that "protein does influence what happens to your lean body muscle mass during the course of any dietary intervention, so there's an important value to eating protein, but it doesn't influence your storage of calories." In an accompanying comment, Zhaoping Li, MD, PhD, and David Heber, MD, PhD, of the University of California Los Angeles, said the study demonstrates "how low-protein foods with hidden sugars or fats may be contributing to the obesity epidemic." "When individuals consume excess carbohydrates out of proportion to protein, the body may gain less weight than when protein is consumed in adequate amounts," they wrote. "Clinicians should consider assessing a patient's overall fatness rather than simply measuring body weight or body mass index, and concentrate on the potential complications of excess fat accumulation." The study was supported by the U.S. Department of Agriculture. Bray reported relationships with Abbott, Takeda, Medifast, Herbalife, Global Direction in Medicine. Co-authors reported relationships with Bristol-Myers Squibb, Eli Lilly, Elcelyx, Merck, Phillips, Catapult Health, and Domain & Associates. The editorialists reported no conflicts of interest. This article was developed in collaboration with ABC News.

Primary source: Journal of the American Medical Association Source reference: Bray GA, et al "Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating" JAMA 2012; 307(1): 47-55. Additional source: Journal of the American Medical Association Source reference: Li Z, Heber D "Overeating and Overweight" JAMA 2012; 307(1): 86-87.   Consuming Excess Calories May Lead To Fat Gain Regardless Of Source. The Wall Street Journal  (1/4, D3, Winslow, Subscription Publication) reports a study  published in the Jan. 4 issue of the Journal of the American Medical Association suggesting that a person's total calorie intake, regardless of the nutritional source of the calories, determines how much fat accumulates in the body.         Bloomberg News  (1/4, Cortez) reports that in the study, 25 healthy participants were "divided into three groups getting a low-protein, high- protein or normal protein diet, with the same calories," and all were given "an extra 1,000 calories a day." Researchers found that participants "getting just five percent of their calories from protein gained significantly less weight than those given more protein, adding 3 kilograms (6.6 pounds), compared with 6 kilograms (13 pounds)," but "low-protein eaters gained just as much fat, and lost lean body mass," compared to high-protein eaters. Researchers concluded that "the results suggest the obesity epidemic may be worse than is currently known because those with lower body weight may have undetected layers of fat that can harm their health."         The Los Angeles Times  (1/4, Stein) "Booster Shots" blog explains, "The normal and high protein groups also saw a substantial increase in their resting energy expenditure -- how many calories the body burns while at rest." This increase in "resting energy expenditure" was not seen for the low protein group.         The Boston Globe  (1/4, Kotz) "Daily Dose" blog details, "In the low-protein group, the body siphoned off 95 percent of the excess calories to pad the body with more fat, burning off five percent as heat while shedding muscle due to a lack of protein. In the higher protein groups, the body used 50 percent of the extra calories for fat while burning off 40 percent as heat and depositing 10 percent into new muscle." In addition, an accompanying editorial  notes, "The study underscores the limitations of relying solely on a bathroom scale to monitor weight over time, especially as the body ages and begins to shed muscle and accumulate fat. ... People can be at a healthy weight on the outside with a high percentage of body fat on the inside and that can lead to many health problems."         Noting an alternative explanation for the weight gain, the ABC News  (1/4, Carollo) "Medical Unit" blog reports, "Dr. Eric Westman, associate professor of medicine at Duke University School of Medicine in Durham, NC, and co-author of 'The New Atkins for a New You,' said the carbohydrate content of the participants' diets could have caused the gains in fat, not the protein. 'Carbohydrates were not manipulated in this study, so you can't say they didn't contribute to the gains,' he said."         According to MedPage Today  (1/4, Fiore), a researcher not affiliated with the study explained, "We also know from other research that protein has a higher thermic effect on food. ... Higher protein intake requires more calories to digest, absorb, and metabolize compared to carbohydrate or fat. This may partly explain the increased calorie expenditure in the normal-to-high-protein groups." Also covering the story are CNN  /Health.com (1/4, Harding), HealthDay  (1/4, Mann) and Reuters  (1/4).