The researchers behind the study analyzed data from the US National Health and Nutrition Examination Survey (NHANES), creating a disease-simulation model to estimate the risk of adults of different body weight developing diabetes and cardiovascular disease.
From this, the researchers then calculated the extent to which overweight and obesity may contribute to both years of life lost and years of healthy life lost in American adults aged between 20 and 79 years old, in comparison to people of normal weight.
They found that people who were overweight (BMI 25-30 kg/m2) were estimated to lose up to 3 years of life, depending on age and gender. Individuals classed as obese (BMI 30-35 kg/m2) were calculated to lose up to 6 years, and people classed as very obese (BMI 35 kg/m2 or more) could lose up to 8 years of life.
According to the study, excess weight had the greatest impact on lost years of life among the young and dropped with increasing age.
Obesity can cause the loss of up to 19 'healthy life-years' As well as reducing life expectancy, carrying extra weight was also found to reduce "healthy life-years," which were defined in the study as years free of obesity-linked cardiovascular disease and diabetes.