Effect of dietary protein on body composition and insulin resistance using a pig model of the child and adolescent

There has been an increase in the incidence of obesity and related metabolic disorders in children and adolescents, so effective dietary and exercise interventions are needed. Over the past decade, there has been growing scientific evidence and public acceptance of the role that dietary protein plays in regulation of satiety, feed intake and obesity-related disorders. Dietary protein appears to suppress food intake and delay the return of hunger more than fats or carbohydrates in a manner not due to energy content alone. Some protein sources, particularly dairy, contain specific peptides or proteins that may elicit direct effects upon satiety. Therefore, the aim of the present study was to investigate the role of level and type of dietary protein using the pig to model the important growth and developmental stages of human life. Increasing dietary protein intake reduced feed intake and fat and weight gain with the response being most pronounced in pigs consuming diets containing soy protein isolate (SPI) rather than whey protein isolate (WPI). However, in female pigs consuming diets rich in SPI from infancy to adolescence, there was a catch-up growth that resulted in increased food intake and weight and fat gain. Insulin sensitivity was negatively related to the rate of fat deposition and was improved in pigs consuming WPI compared with SPI. While high-protein diets may decrease calcium balance and bone strength, it appears that these effects are attenuated by WPI. These findings suggest that high-protein diets may reduce hunger and food intake, thereby reducing fat deposition and improving insulin sensitivity.