Researchers examined trends in carbohydrate, fat and protein intakes in adults and their association with energy intake (calories) by tracking intake over time using data from the National Health and Nutrition Examination Survey (NHANES) — a program of studies designed to assess the health and nutritional status of adults and children in the United States.
One of the most striking findings was the consistently strong and negative association with increasing percentage calories from protein and daily energy intake across all three body mass index categories (normal weight, overweight and obese) in both NHANES I, 1971-75, and NHANES 2005–2006, according to the study.
This finding may surprise many as it contradicts the belief that the rise in obesity has been caused by increased caloric intake due to the overconsumption of protein-based foods.
Research showed that in NHANES 2005–2006, a 1% increase in the percentage of energy from protein was associated with a decrease in energy intake (calories) of 32 kcal (substituted for carbohydrates) or 51 kcal (substituted for fat). Similar findings were seen across all body mass index categories, in men and women, and in NHANES I.
“This finding is all the more interesting given the exclusion of individuals following any type of special diet [such as low-carbohydrate or high-protein diets] and supports human experimental data in obese individuals that a high-protein diet can be more effective at increasing satiety, reducing hunger and energy intake, and achieving greater weight loss,” the researchers said. “The decrease in energy intake was greater if protein was substituted for fat, but the effect was still substantial when protein was substituted for carbohydrates.”
They added a shift toward more carbohydrates during the years examined was associated with an overall increase in energy intake and an increase in obesity prevalence, and concluded, “Dietary interventions to combat the obesity epidemic should focus on reducing total energy intake, perhaps by substituting protein intake in place of both carbohydrate and fat intake.”