In Pennington's study, 25 participants aged 18-35 spent 10-12 weeks living in a monitored metabolic unit.
During the first few weeks, participants were fed a normal diet after determining a daily caloric intake level that would not change their current weights. However, in the final eight weeks of the study, participants were overfed by 954 calories a day.
Study participants were assigned to one of three diets -- a low protein diet containing 5% of calories from protein, a normal protein diet containing 15% of calories from protein or a high protein diet containing 25% of calories from protein. Carbohydrate intake was the same among all diets.
Participants were given food that met their dietary requirements, monitored to ensure everything was eaten and discouraged from exercise.
The study found all participants gained weight over the three-month investigation period. Those assigned the low protein diet lost lean body mass, while the other two groups gained it.
Those in the low protein group gained less weight than the higher protein groups, but more of the excess calories were stored as fat.
According to the study, 90% of the extra energy in the low protein group was stored as fat, whereas 50% was stored as fat for the other diet groups.
George Bray, chief of Pennington's Division of Clinical Obesity and Metabolism and a researcher on the study, summarized the results saying, "In a controlled setting, the increase in body fat during overeating is determined by the excess caloric intake. Protein affects thermogenesis (energy expenditure) and gain of lean body mass, but not body fat."
Bray said he and the rest of the research team were interested in the subject because they wanted to investigate ideas from past studies.
"Some earlier research suggested that if you ate a low-protein diet you might ‘waste' calories. This is clearly not the case, but it was an interesting hypothesis to test," Bray said.
Vanessa Richard, Student Health Center dietitian, said gaining body fat is dangerous because it can increase risk for chronic diseases later in life.
One could be a normal weight, or even underweight, and still have an above-normal percentage of body fat, Richard said.
"Just because someone is thin doesn't mean their body is healthy on the inside," she said.
Richard said body weight is not an accurate measure, as it's impossible to determine if fat or muscle is being gained or lost. A body composition analysis is more accurate, she said. She recommends eating consistently throughout the day and "frontloading" calories, or eating a substantial breakfast in lieu of a large dinner.
Bray recommends consuming a diet comprising 15-18% of protein, with high fruit and vegetable intake and low-fat dairy products.
The results of this study will be reviewed when the Dietary Guidelines Panel reconvenes in 2015, Bray said. The results could possibly lead to an increase in the national recommended daily protein intake.
"I'd encourage people to take the ideas from this study and apply them to their daily lives, in combination with general balanced eating," Richard said.
From the February 9, 2012, Prepared Foods' Daily News.