Impact of the national steps challenge physical activity programme on obesity and type 2 diabetes prevalence in Singapore to 2050: simulation-based forecasting analysis.

Background: The National Steps Challenge (NSC) is a physical activity intervention that has enrolled over 2.1 million people in Singapore across 9 years. The impacts of this intervention on current and future obesity, and type 2 diabetes mellitus (T2DM) prevalence are currently unknown. Here, we estimate population-level impacts and explore future scenarios in how physical activity interventions could mitigate rising obesity and T2DM burdens. Methods: Using a microsimulation model of 7.9 million Singapore residents and NSC participation data, we modelled the associated effects of physical activity on BMI trajectories and T2DM prevalence across the Singaporean population from 1990 to 2050 by ethnicity, sex, age, and body-mass-index subgroups. We then simulated five programme scenarios, ranging from no NSC to full population-wide deployment, projecting estimated future prevalences. Findings: Without the NSC, total obesity prevalence was projected to rise from 13.6% (total n = 261,675) in 1990 to 32.4% (total n = 1,189,081) by 2050, and T2DM from 5.8% (total n = 111,597) to 16.0% (total n = 587,200). Based on current recruitment and programme retention rates, relative to the No NSC, total obesity and T2DM prevalence could be lowered by 4.8% (1.5%-8.1%; n = 179,380) and 1.2% (0.3%-2.8%; n = 36,407), respectively, by 2050. These reductions are estimated to vary substantially by ethnicity and sex, and programme scenario. Interpretation: Physical activity programmes such as the NSC can help mitigate rising obesity and T2DM prevalence when implemented at the population level, as seen in Singapore. However, their success depends on robust digital infrastructure and sustained incentivisation to enhance long-term impact. Funding: This research was supported by the Population Health Metrics and Analytics project, the Ministry of Health.