Relationship between sex of parent and child on weight loss and maintenance in a family-based obesity treatment program

Objective: To determine if the sex of the participating parent/child pair is a contributing factor in initial weight loss and maintenance within a family-based obesity treatment program. Design: A 2-year family-based obesity treatment program targeting one overweight parent and one overweight child. Subjects: One overweight parent (body mass index (BMI) >= 25) and child (>= 85th BMI percentile) from 164 families. Measurements: Parameters of body weight, including height, weight, BMI, z-BMI, percent overweight (BOV) at baseline and at 6-, 12- and 24-month follow-up time points. Results: Children within the opposite-sex dyads had greater weight loss (P < 0.01) at 6- and 12- month time points compared with children in the same-sex dyads. Parents within opposite-sex dyads had significantly greater weight loss at 24 months (P < 0.05) compared with those in the same-sex dyads. When individual dyads were examined, the change in child z-BMI after 6 months was greater for the mother-son dyad as compared to the mother-daughter and father-son (P < 0.05). For parent z-BMI, the mother-daughter dyad consistently exhibited the poorest results. At 6- and 12- month time points, parents in the mother daughter dyad lost significantly less weight than parents in all other dyads (P < 0.05), and at 24 months, parents in the mother daughter dyad lost less weight than parents in the opposite-sex dyads (P < 0.05). Conclusion: These data reveal that child-parent sex interactions can strongly influence the outcome of obesity treatment when both parent and child are the target for weight loss. The reasons that underlie this effect remain to be determined.