Growth patterns early in life could exert a long-term impact on overweight and obesity development. Among all potential manipulative factors, infant diet is one of the most influential and could affect growth and subsequent health status during adolescence and adulthood. Dietary protein, as an important macronutrient in infants' diet, has been of special interest to researchers. Compared with human milk, infant formula tends to have a higher protein content and is associated with greater weight gain and later-in-life obesity risk. However, the effect of protein from other sources on infant growth trajectories during complementary feeding is not clear. Emerging research suggests that meat protein during early complementary feeding promotes linear growth while not increasing risk of overweight compared with dairy protein; and the gut microbiota might be a mediator between protein quality and growth trajectories. This review addresses the current knowledge of protein intake from birth to 24 months and its relationship with growth and risk of overweight.
Keywords: complementary feeding; growth; protein; the gut microbiome.