Childhood obesity remains a major health challenge, and effective interventions often require more than nutritional guidance and exercise plans. The structure of the day, family routines, school schedules, and holiday interruptions can affect how children eat, move, sleep, and spend screen time. In the Southern Hemisphere, summer vacation can reduce daily routines for an extended period of time, making it more difficult to maintain healthy habits. Seasonal patterns are discussed in international studies, but evidence from New Zealand is limited. Based on these challenges, more detailed research is needed to determine whether season of program entry influences outcomes of obesity interventions in children and adolescents.
Researchers from the University of Auckland, New Zealand Ministry of Health Te Whatu Ora Taranaki, Chiang Mai University, Curtin University and associated institutions reported the study conducted online on 6 February 2026 (DOI: 10.1007/s12519-025-01016-z). World Pediatric Journal. The researchers analyzed 397 children and adolescents enrolled in Whānau Pakari, a multidisciplinary community-based healthy lifestyle program in New Zealand, to examine whether the season of enrollment affected changes in BMI results during the first six months of the intervention.
This study used a combination of traditional statistical models and random forest analysis to examine outcomes for participants aged 3.7 to 16.8 years. Overall, 68% of patients had a lower BMI standard deviation score at 6 months, with a mean decrease of 0.16. However, the pattern changed when considering the season. Children entering summer, fall, and winter all experienced significant improvements in BMI, whereas children entering spring did not experience a significant decline. Compared to spring entrants, the decline in fall and winter entrants was greater, and summer entrants showed a similar trend. Researchers suggest spring participants may be at a disadvantage because the first six months of treatment include a long summer break from school. During this period, daily activities tend to decrease and efforts tend to be weaker. The program produced further broader benefits, including reduced sugary drink intake, increased physical activity, reduced screen time, and a modest increase in fruit and vegetable intake. Random forest modeling added another layer. Higher baseline BMI and younger age were the strongest predictors of improvement, but once lifestyle changes were included, the effect of season of entry was greater than any single reported behavior.
“This study illustrates a practical but often overlooked truth: timing determines the success of treatment,” the findings suggest. “Children who enter a program just before a long, unstructured break may face a very different path than those who start at a more stable time of the year. This means that poorer short-term outcomes do not necessarily reflect reduced motivation or poor program quality. Rather, they may reveal how strongly children’s health behaviors are tied to routines, supervision, and the daily structure provided by school terms.”
The impact goes beyond just one program in New Zealand. For clinicians, schools, and public health planners, the results of this study suggest that obesity interventions may work more effectively if timing is incorporated into the program design. Holiday-specific support, special contact during breaks, and longer follow-up periods may help prevent seasonal bias and improve the equity of results. The study also cautions against hastily determining the value of a program based on a single checkpoint every six months. Success in pediatric obesity care is not just about weight loss in the narrow sense of the term, but also about slowing unhealthy weight gain while supporting healthier lifestyles during growth.
sauce:
Chinese Academy of Sciences
Reference magazines:
Delike, Japanese government bonds, Others. (2026). Seasonal variation in BMI results after 6 months: A secondary analysis of a multidisciplinary healthy lifestyle program for obese children and adolescents. World Pediatric Journal. DOI: 10.1007/s12519-025-01016-z. https://link.springer.com/article/10.1007/s12519-025-01016-z
