**Background:** Childhood overweight and obesity affect nearly 1 in 5 (18%) school-age children globally, with rising prevalence in nearly all regions. Obesity is increasingly understood as a complex, 'wicked' challenge requiring whole systems approaches that address multifactorial drivers across sectors. While such approaches have been promoted for over a decade, questions remain about operationalization. Brighton and Hove, UK, has been recognized for lower child obesity rates than most UK cities and innovative food approaches, including being the first UK city to receive a Gold Sustainable Food Cities award in 2021. This study examines the processes behind Brighton's success to inform other municipalities.
**Methods:** The study employed a mixed-methods approach including: (1) a background review of literature and data on childhood obesity prevalence, social determinants, and policy environments in Brighton over the past ten years; (2) twelve key informant interviews (KIIs) involving thirteen participants conducted virtually between November 2020 and March 2021, lasting 45-90 minutes each. Interviewees included public health team members (n=3), NHS children's health/early years staff (n=2), community-based organization representatives (n=4), and broader local authority team members (n=3). Data were analyzed using the Baker et al. (2018) framework on political commitment to nutrition, with coding performed in NVivo 12. Findings were validated through sharing a chronology of events with participants and a virtual validation event with 14 stakeholders in September 2021.
**Key Results:** Data from the National Child Measurement Programme (NCMP) show that Brighton's childhood obesity rates have been consistently below national and regional (South East) averages from 2006-2019. Reception-age (4-5 years) rates fell below national average since 2012-13, while year 6 (10-11 years) rates have been consistently below national average and declined between 2009-10 and 2012/13 during a period when the national trend was rising. However, from 2014-2019, obesity in the most deprived quintiles was twice as high as the least deprived (25.8% vs. 12.8% among year 6 children), with an inequalities gap larger than the national average. In Moulsecoomb and Bevendean, overweight and obesity among reception-age children was 30.4% (2016-17 to 2018-19), significantly higher than the national average of 22.5%, compared to just 12.5% in affluent Preston Park. Ethnic disparities exist: among year 6 children, obesity prevalence was 12.5% for white children, 19.7% for Asian children, and 25.5% for Black children. Brighton ranks 5th nationally for breastfeeding at 72.3% (any breastfeeding at 6-8 weeks) vs. 48% England average, with exclusive breastfeeding at 55.5% (highest in England). In 2018, 69% of primary school pupils aged 8-11 ate five or more portions of fruit/vegetables daily, while only 31% met recommended physical activity levels. Key success factors identified included: a supportive local political context with cross-party consensus; strong partnership working facilitated by the Brighton & Hove Food Partnership and the Healthy Weight Program Board (formed 2013); long-term commitment to early years interventions (15+ years of breastfeeding promotion); community-tailored approaches responsive to local needs; effective use of data for targeting; and external frame resonance through campaigns like Sugar Smart. Challenges included: difficulty engaging families in weight management services due to stigma; low GP referral rates; limited reach to secondary schools; funding constraints from a decade of austerity policies; and persistent inequalities in deprived areas where food environments offer fewer healthy options and physical infrastructure is poorly maintained.
**Clinical Implications:** This case study demonstrates that a whole systems approach combining cross-sectoral governance, political commitment, community engagement, and targeted interventions can achieve population-level improvements in childhood obesity, even within a challenging national policy context of austerity. The findings suggest that success requires: devolved authority enabling local innovation; sustained political commitment across administrations; strong partnership brokering by non-governmental organizations; strategic use of data for targeting deprived areas; and long-term investment in early years interventions. However, the persistent and widening inequalities gap—with obesity rates in deprived areas double those in affluent areas—highlights that whole systems approaches must explicitly address upstream social determinants including income, housing, and employment. The COVID-19 pandemic exacerbated these challenges, with food bank usage in March 2021 remaining almost four times higher than July 2019 (1,825 families per week vs. 420). National-level recommendations from stakeholders include banning junk food advertising to children, reinstating the national infant feeding survey, and implementing current food strategy recommendations, while local recommendations emphasize co-production with communities, targeting secondary school food environments, and embedding healthy weight principles in planning and transport policy.