How was the study conducted?
Led by author Prof. Sue Shapses of nutritional sciences at the Rutgers School of Environmental and Biological Sciences and co-author Anna Ogilvie, a doctoral student at the Department of Nutritional Sciences, the study was published in the peer-reviewed journal Obesity.
The researchers gathered data for over 20 years from 200 individuals between the ages of 24 and 75 in clinical trials at the university funded by the US National Institutes of Health. Their Body Mass Index classified them as either overweight or obese. As part of the study, they were told to follow a 500-calorie-deficit diet and attend nutrition counseling in order to lose weight over six months.
The researchers analyzed data from the trials and found that even minor increases in protein in people's diets from 18% to 20% have a measurable effect on the choices they make with regard to healthy eating.
“It’s somewhat remarkable that a self-selected, slightly higher protein intake during dieting is accompanied by higher intake of green vegetables, and reduced intake of refined grains and added sugar,” Shapses said. “But that’s precisely what we found.”
Impact on lean body mass, micronutrient intake
“The impact of self-selected dietary protein on diet quality has not been examined before, to our knowledge, like this.”Anna Ogilvie, Department of Nutritional Sciences, Rutgers School of Environmental and Biological Sciences
The researchers also concluded from the analysis that a moderately increased protein intake also decreases the loss of lean body mass.
Furthermore, Rutgers noted, weight loss regimens that include restrictions on calories are linked to a reduction in the consumption of healthy foods containing micronutrients including iron and zinc. Eating larger amounts of protein is associated with healthier outcomes, but the relationship between protein consumption and overall diet quality is not yet fully understood.
“The impact of self-selected dietary protein on diet quality has not been examined before, to our knowledge, like this,” said Ogilvie. “Exploring the connection between protein intake and diet quality is important because diet quality is often suboptimal in the US, and higher-protein weight loss diets are popular.”