Milk fat intake, adiposity, and obesity in Canadian children: findings from the prospective Canadian CHILD Cohort Study

BACKGROUND: Guidelines in Canada, the United States, and other countries recommend that children switch from whole (3.25%) to reduced-fat milk after age 2 years to limit saturated fat intake and prevent obesity, despite these recommendations being derived primarily from adult studies. Emerging pediatric evidence challenges this approach, but prospective data in early school-aged children are scarce. OBJECTIVES: To test for cross-sectional and longitudinal associations of cow milk-fat content at age 5 years and adiposity indicators and obesity status among 5- and 8-year-old Canadian children. METHODS: We analyzed data from the CHILD Cohort Study, a national longitudinal prospective pregnancy cohort study. At age 5 years, caregivers reported the fat content of cow milk consumed (skim [0%], 1%, 2%, and whole [3.25%]). Anthropometric measures at ages 5 years (N = 2043) and 8 years (N = 1574) included body mass index (BMI) and waist-to-height ratio z-scores; and at age 8 years, fat mass percentage (measured by bioelectric impedance analysis) and obesity (defined using World Health Organization criteria and the new clinical obesity Lancet Commission definitions). Multivariable linear and logistic regression models were adjusted for sociodemographic, lifestyle, and other dietary factors. RESULTS: At age 5 years, most children consumed 2% (48.9%) or 3.25% (23.9%) fat from cow milk. Compared with skimmed cow milk, whole (3.25%) cow milk consumption was associated with lower BMI z-score at age 5 years [β: -0.34; 95% confidence interval (CI): -0.54, -0.13] and lower odds of living with obesity [odds ratio (OR): 0.22; 95% CI: 0.07, 0.67]. Whole cow milk consumption at 5 years was also inversely associated with BMI z-score (β: -0.42; 95% CI: -0.72, -0.11), waist-to-height ratio z-score (β: -0.35; 95% CI: -0.63, -0.07), fat mass (β: -1.58; 95% CI: -3.10, -0.06), obesity (OR: 0.31; 95% CI: 0.12, 0.80), and preclinical obesity (OR: 0.25; 95% CI: 0.09, 0.70) at age 8 years. CONCLUSIONS: Whole cow milk consumption at age 5 years was associated with lower adiposity and obesity indicators in middle childhood. These findings challenge current recommendations to limit milk fat in children and may inform future dietary guidelines.