The study was published in the New England Journal of Medicine. Researchers from the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) study found similar weight loss after six months and two years among participants assigned to four diets that differed in their proportions of these three major nutrients.
For the study, 811 overweight and obese adults aged 30 to 70 years (38% male) were assigned to 1 of 4 diets and asked to record their food intake in a diary or an online tool that showed how intake compared with goals. Group diet counselling sessions were held at least twice per month throughout the two years of the study, and individual sessions were held every eight weeks.
The nutrient compositions of the four diets were: (1) 20% fat, 15% protein, 65% carbohydrate; (2) 20% fat, 25% protein, 55% carbohydrate; (3) 40% fat, 15% protein, 45% carbohydrate; or (4) 40% fat, 25% protein, 35% carbohydrate. The diets all used the same calorie reduction goals and were low in saturated fat and cholesterol while high in dietary fibre.
Participants were given personalised calorie goals (1200-2400 calories per day), which reduced their overall caloric intake as compared with their daily energy requirement. All participants were asked to do moderate-intensity physical activity for at least 90 minutes per week. Participants did not have diabetes or severe heart disease but could have had other risk factors, such as hypertension or high cholesterol.
On average, participants lost 6.5 kg at six months and maintained a 4.5 kg loss at two years. Participants also reduced their waistlines by the end of the study. Craving, fullness, hunger, and diet satisfaction were all similar across the four diets.
All diets improved risk factors for cardiovascular disease at both six months and two years in ways consistent with previous studies. Improved risk factors included reduced levels of triglycerides, low-density lipoprotein cholesterol, lowered blood pressure, and increased high-density lipoprotein cholesterol. All diets decreased the presence of metabolic syndrome.
Previous studies have shown that a loss of 5% to 10% of body weight will help reduce risk factors for heart disease and other medical conditions. In the current study, 15% of patients achieved a 10% weight loss after two years.
While the design of the study called for physical activity targets to be set at 90 minutes per week, many people need more physical activity in order to achieve their weight loss goals.
