The evidence that fetal life and early infancy are "critical" or "sensitive" ages for later cardiometabolic disease is based on flawed methods for comparing different age periods. Moreover, most previous studies have limited their focus to weight gain, rather than growth in length/height or body mass index (BMI). We undertook a secondary analysis of PROBIT (1996-2010), a birth cohort study nested within a large cluster-randomized trial in the Republic of Belarus, with repeated measures of weight and length/height from birth to 11.5 years of age. We used mixed effects linear models to analyze associations of changes in standardized weight, length/height, and BMI during five age periods (conception to birth, birth to 3 months, 3 to 12 months, 12 months to 6.5 years, and 6.5 to 11.5 years) with fasting glucose, insulin, insulin resistance, β-cell function, and adiponectin at age 11.5 years. We observed strong associations between the metabolic markers and all three growth measures, with the largest magnitudes observed during the latest age period (6.5 to 11.5 years) and negligible associations during gestation and the first year of life. Later age-periods appear more "sensitive" than earlier periods to the adverse metabolic association of rapid growth in childhood.