New Evidence Backs More Dietary Protein to Control Weight

Laird Harrison

June 16, 2015

SAN DIEGO — Adding more protein might help control weight in people older than 45 years, a new study suggests.

"We're seeing improvements in body weight and body fat percentage," researcher Ann Brown, from Florida State University in Tallahassee, told Medscape Medical News.

The study provides evidence that the Institute of Medicine's Dietary Reference Intake for Estimated Average Requirements for protein in older people should be increased, she said.

Brown presented the results here at the American College of Sports Medicine 62nd Annual Meeting.

Previous research has suggested that high-protein diets can reduce obesity, but results on body composition have been mixed, the researchers report.

In their study, Brown and her colleagues analyzed data from the Boston Puerto Rican Health Study (BPRHS), an ongoing study of 960 people of Puerto Rican descent who are 45 to 75 years of age and live in the Boston area.

Health complications from obesity are particularly common in Hispanic Americans, they explain.

For the 690 women in the sample, average age was 60 years and mean body mass index (BMI) was 32 kg/m². For the 296 men, average age was 59 years and mean BMI was 30 kg/m².

After adjustment for the total amount of energy consumed, participants who consumed the highest proportion of protein in their diets had lower BMIs, smaller waist circumferences, and higher muscle-to-fat ratios.

Table: Variables by Tertile of Protein Consumption

Variable Least Protein Medium Protein Most Protein
Women      
   n 191 236 255
   Protein as % of total energy 15.9 17.1 19.1
   Daily protein consumption, g/kg body weight 1.2 0.9 0.9
   BMI, kg/m² 36.1 33.5 29.9
   Waist circumference, cm 109.5 104.5 97.8
   Lean mass, % 50.4 51.9 54.3
Men      
   n 126 81 61
   Protein as % of total energy 16.5 17.3 19.9
   Daily protein consumption, g/kg body weight 1.4 0.9 0.9
   BMI, kg/m² 31.8 28.9 28.0
   Waist circumference, cm 108.4 101.3 98.9
   Lean mass, % 64.5 67.2 69.2

Protein makes a person feel more satisfied than carbohydrates, said Brown. "Simply because they are feeling more full, they are eating less."

In adults, the Dietary Reference Intake for protein is 0.66 g/kg of body weight per day. In this study, daily protein consumption ranged from 0.9 to 1.4 g/kg.

A recommendation of 1.1 to 1.2 g/kg daily might produce better health effects, Brown said. Protein generally doesn't cause harmful effects below about 4 g/kg per day, she added.

According to Nancy Clark, RD, who is a sports nutritionist in Boston, most people in her field agree that 1.0 to 1.5 g/kg per day would be "an appropriate range" for older people. "As people grow older, their protein needs increase," she explained.

But changing the Dietary Reference Intake values is difficult; "it gets into politics," she pointed out. "If you change the protein requirements, that changes all kinds of lunch programs and food assistance programs."

So far, it hasn't been a high priority because most people eat more protein than the current recommendation, she said.

Rather than focusing on a daily value, she said she would rather make sure that "people have protein at each of their meals so the muscles have a constant supply of amino acids, and therefore a constant supply of tools to repair and build and prevent frailty with age."

Ms Brown and Ms Clark have disclosed no relevant financial relationships.

American College of Sports Medicine (ACSM) 62nd Annual Meeting: Abstract 407. Presented May 27, 2015.

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