The evolving burden of obesity in the US: a novel population-level system dynamics approach

The prevalence of obesity in US adults exceeds 40%. Trends suggest this epidemic will worsen. We developed a dynamic population-based model to forecast US obesity population dynamics from 2023-2060. We aimed to assess whole-system burden of obesity from multiple perspectives and explore the impacts of targeted interventions.

The model uses population dynamics and epidemiology in differential equations to describe populations in BMI- and age-compartments over time. Calibration used pre-2020 NHANES data. Holistic burden of excess BMI was calculated by multiplying prevalence with rates of associated outcomes. We quantified where intervention yields greatest value by simulating reductions in progression rates between BMI categories.

By 2060, we project US adult obesity (BMI ≥ 30 kg/m²) prevalence will increase to 50.5%. Direct obesity-attributable healthcare costs were estimated at $20.4tn cumulatively [2023-2060]. A 37% increase in obesity-related complications (ORCs) contributes to 79% and 35% more primary care contacts and hospitalizations per annum, respectively. A 73% rise in BMI-related mortality results in 31 m excess cumulative deaths. The cumulative cost of lost quality-of-life (QoL) may exceed $161.3tn. Reducing progression from overweight (25 kg/m² ≤ BMI < 30 kg/m²) to obesity class I (30 kg/m² ≤ BMI < 35 kg/m²) has the greatest impact on obesity prevalence, avoiding 25 m cases in 2060, with cumulative reductions of $1.21tn in direct medical costs, $3.1tn in indirect costs, 745 m ORCs, 132 m hospitalizations, 220,000 obesity-related deaths, and $12.5tn in lost QoL by 2060. Reducing progression from obesity class II (35 kg/m² ≤ BMI < 40 kg/m²) to obesity class III (BMI ≥ 40 kg/m²) is associated with marginally greater cumulative savings in direct medical costs but averts fewer deaths.

Our projections are based on data collected prior to large-scale uptake of anti-obesity medications. Modelling assumptions may present limitations.

Preventing obesity is preferable to managing prevalent obesity, with superior holistic benefits, especially if focused on younger people.