Impact of overweight, obesity and severe obesity on life expectancy of Australian adults

Background/objectives: Adult obesity has been shown to substantially heighten the risk of adverse health outcomes but its impact on life expectancy (LE) has not been quantified in Australia. Our aim is to estimate reductions in LE and years of life lost (YLL) associated with overweight and obesity, relative to those at a healthy weight for Australian adults aged 20-69 years. Subjects/methods: We used a microsimulation model of obesity progression in Australia that integrates annual change in BMI based on age and sex, with Australian life-table data and published relative risk of all-cause mortality for different BMI categories. Remaining LE and YLL compared to healthy weight were estimated using 10-year cohorts, by sex. A nationally representative sample of 12,091 adults aged 20-69 from the 2014/15 Australian National Health Survey were used to represent the input population of 14.9 million. Results: Estimated remaining years of LE for healthy weight men and women aged 20-29 years was approximately 57.0 (95% CI 56.7-57.4) and 59.7 (95% CI 59.4-60.0) years, respectively. YLL associated with being overweight at baseline was approximately 3.3 years. For those obese and severely obese the loss in LE was predicted to be 5.6-7.6 years and 8.1-10.3 years for men and women aged 20-29 years, respectively. Across men and women, excess BMI in the adult population is responsible for approximately 36.3 million YLLs. Men stand to lose 27.7% more life years compared to women. Conclusions: Overweight and obesity is associated with premature mortality at all ages, for both men and women. Adults aged 20-39 years with severe obesity will experience the largest YLL, relative to healthy weight. More needs to be done in Australia to establish a coherent, sustained, cost-effective strategy to prevent overweight and obesity, particularly for men in early adulthood.