This study reviewed data from 57 prospective studies involving 894,576 participants with the aim of assessing the associations between body mass index (BMI) and overall and cause-specific mortality. The studies were mainly conducted in North America and Western Europe. The average age of participants at enrolment was 46 years and 61% were male.
The study found that mortality was lowest in individuals with a BMI in the range of 22.5-25 kg/m2. Overall mortality increased by 30% for each additional 5 kg/m2 increase in BMI.
When mortality was analysed by specific causes a 5 kg/m2 increase in BMI was associated with a 40% increase in vascular mortality, 120% increase in diabetic mortality, 60% increase in renal mortality and 80% increase in hepatic mortality.
A press release issued by CTSU estimates that moderate obesity (BMI 30-35 kg/m2) reduces life expectancy by 3 years and severe obesity (BMI 40-50 kg/m2) by 10 years. A 10 year reduction in life expectancy is equivalent to that seen in lifelong smokers. It was also noted that the additional risks posed by smoking and high BMI were additive.
Action: Clinicians will find this research useful when communicating the risks of obesity to patients. These data show that a severely obese smoker is likely to have a reduction in life expectancy of 20 years.