Early protein intake and later obesity risk: which protein sources at which time points throughout infancy and childhood are important for body mass index and body fat percentage at 7 y of age?

BACKGROUND: A high early protein intake has been proposed to increase obesity risk.
OBJECTIVE: We examined whether a critical period of protein intake for later obesity may exist early in childhood and investigated the relation between protein intake from different sources and body mass index SD score and body fat percentage (BF%) at 7 y of age.
DESIGN: The study population included 203 participants of the Dortmund Nutritional and Longitudinally Designed Study with information on diet at 6 mo, 12 mo, 18-24 mo, 3-4 y, and 5-6 y. Life-course plots were constructed to assess when protein intake (% of energy) was associated with body mass index SD score and BF% at 7 y. Mean values were then compared among tertiles (T1-T3) of protein from different sources at the important time points.
RESULTS: The ages of 12 mo and 5-6 y were identified as critical ages at which higher total and animal, but not vegetable, protein intakes were positively related to later body fatness. In fully adjusted models, animal protein intake at 12 mo was associated with BF% at 7 y as follows [x (95% CI) BF%]: T1, 16.20 (15.23, 17.25); T2, 17.21 (16.24, 18.23); T3, 18.21 (17.12, 19.15); P for trend = 0.008. With respect to food groups, dairy, but not meat or cereal protein intake, at 12 mo was related to BF% at 7 y (P for trend = 0.07). Animal protein at 5-6 y yielded similar results (P for trend = 0.01), but food group associations were less consistent.
CONCLUSION: A higher animal, especially dairy, protein intake at 12 mo may be associated with an unfavorable body composition at 7 y. The age of 5-6 y might represent another critical period of protein intake for later obesity risk.