Cow Milk Fat Obesity pRevention Trial (CoMFORT)

Cow's milk is a dietary staple for children in North America. Though clinical guidelines suggest children transition from whole (3.25% fat) milk to reduced (1%) fat milk at age 2 years, recent epidemiological evidence supports a link between whole milk consumption and lower adiposity in children. The purpose of this trial is to determine which milk fat recommendation minimizes excess adiposity and optimizes child nutrition and development. CoMFORT will be a parallel group randomized controlled trial among children aged 2 to 4 years participating in the TARGet Kids! practice-based research network. Children will be randomized to receive one of two usual care nutritional recommendations: 1) a recommendation to consume whole milk, or 2) a recommendation to consume reduced (1%) fat milk. The primary outcome is Body Mass Index z-score (zBMI); secondary outcomes will be cognitive development (using the Ages and Stages Questionnaire), vitamin D stores (serum 25-hydroxyvitamin D), cardiometabolic health (glucose, hsCRP, non-HDL, LDL, triglyceride, HDL and total cholesterol, insulin, and diastolic and systolic blood pressure) and sugar sweetened beverage intake (measured by 24-hour dietary recall). Outcomes will be measured 24 months post-randomization and compared using ANCOVA, adjusting for baseline measures. This trial will contribute to nutrition policy for children in effort to reduce childhood obesity using a simple, inexpensive and scalable cow's milk fat intervention.

Children randomized to the whole milk recommendation will receive a recommendation a primary care recommendation to consume 500 mL of whole fat (3.25%) milk instead of transitioning to reduced fat (1%) milk at 2 years of age. The primary care physician will verbally make this recommendation during the recruitment well-child visit. Parents will also be reminded bi-monthly by phone calls made by a research assistant. Children in the whole milk recommendation group will be provided with the same age-appropriate nutritional recommendations as children in the reduced fat recommendation group as part of routine healthcare according to the Rourke Baby Record.

Children randomized to the reduced fat group will receive a primary care recommendation to transition from whole milk to 500 mL reduced fat (1%) milk daily once the child is two years of age (consistent with current guidelines). The physician will verbally make this recommendation during the recruitment well-child visit. Parents will also be reminded bi-monthly by phone calls made by a research assistant. Children who receive the reduced fat recommendation will be provided with the same age-appropriate nutritional recommendations as children who receive the whole fat recommendation as part of routine healthcare according to the Rourke Baby Record.

BMI calculated by weight (kg)/height (m^2); zBMI determined according to the World Health Organization guidelines

measured using the Early Development Instrument (EDI); children scoring at or below the 25th percentile of children in their province are considered at risk for continuing on the low achievement and health trajectory, and are more likely to fall behind in academic achievement in later grades

All costs, parameter estimates and ranges will be derived from study data and will be obtained using medical record extraction. Publicly available Ontario costing sources will be used to cost resource utilisation parameters.

Inclusion Criteria: healthy by parental report; 1.5 to 2.99 years of age involved in a TARGet Kids! academic pediatric or family medicine group. Exclusion Criteria: Prader-Willi syndrome or other syndrome associated with obesity severe development delay children who are from families without verbal communication in English or French failure to thrive (with zBMI values ≤ -2 are unlikely to benefit from obesity prevention) siblings of trial participants as families may share milk will not consume cow's milk by choice, lactose intolerance or allergy.

Vanderhout SM, Aglipay M, Birken C, Li P, O'Connor DL, Thorpe K, Constantin E, Davis MA, Feldman M, Ball GDC, Janus M, Juni P, Junker A, Laupacis A, L'Abbe M, Manson H, Moretti ME, Persaud N, Omand JA, Relton C, Wong P, Yamashiro H, Tavares E, Weir S, Maguire JL. Cow's Milk Fat Obesity pRevention Trial (CoMFORT): a primary care embedded randomised controlled trial protocol to determine the effect of cow's milk fat on child adiposity. BMJ Open. 2020 May 7;10(5):e035241. doi: 10.1136/bmjopen-2019-035241.