The age at which body mass index (BMI) increases after its nadir in childhood, adiposity rebound (AR), is a critical period for the development of obesity. Children with early AR are at substantially increased risk of adult obesity. Few studies have examined the factors that influence the timing of the AR. The aims of this study were to test for influences on the timing of the AR, and to test the hypothesis that early AR is promoted by high-protein intake.Longitudinal cohort study of 889 children representative of the United Kingdom, followed from birth to 5 years.We tested for differences in dietary intake, parental BMI, socioeconomic status, and childhood BMI between 3 groups of children characterized by the following: very early AR (at or before 43 months), early AR (from 49 but before 61 months), and later AR (after 61 months).There was no evidence of associations between dietary protein intake, or any other dietary variable, and timing of the AR. Children with very early AR and early AR had parents with significantly higher BMI, and were significantly more likely to have at least 1 obese parent.This study does not support the hypothesis that early AR is promoted by high-protein intake. None of the dietary variables tested were significantly associated with timing of the AR, and timing of AR was not associated with socioeconomic status. Parental obesity was associated with an earlier AR.