The study by Switkowski et al. (1) published in this journal showed that early childhood protein intake may contribute to programming lean mass and insulin-like growth factor I (IGF-I) around the time of puberty in boys but not to adiposity development, and it concludes that these results do not support previous findings that protein intake in early childhood programs adiposity development in well-nourished children. The authors stress that inconsistencies may be due to differences in the timing of exposure. The studies showing associations between high protein intake and later fatness development were often conducted in children younger than age 2 y at the time of exposure (2–5). In a systematic literature review, Hörnell et al. (6) concluded that higher protein intake in infancy and early childhood was convincingly associated with increased growth and higher BMI in childhood and that the first 2 y of life were likely to be most sensitive to high protein intake. Following similar observations, a review by Michaelsen and Greer (7) concluded that it seems prudent to avoid a high protein intake during the first 2 y of life.