A new study of long-term follow-up from 10 population-based cohorts challenges the so-called obesity paradox , previous counterintuitive findings suggesting that patients with heart disease may live longer if they are overweight or obese. The study was published in JAMA Cardiology.

A study differs from previous studies in that they have included a lifespan perspective, they started to follow people before they developed heart disease," lead author, Sadiya Khan. They found that obese people live shorter lives, and while overweight people had similar length of life to those of a normal weight, they developed cardiovascular disease earlier than people with normal BMI.

When you take a population with any chronic condition you see a different picture which may not tell the truth. We also have to consider when the patient developed heart disease. By starting to follow people before they developed heart disease, these researchers have removed one of the biggest confounders.

The study analyzed individual-level data from 190,672 in-person examinations across 10 large prospective cohorts with an aggregate of 3.2 million years of follow-up. All of the participants were free of CVD at baseline and had objectively measured height and weight to assess BMI. Results showed that compared with individuals with a normal BMI (defined as a BMI of 18.5 to 24.9), lifetime risks for incident CVD were higher in people in the overweight (BMI, 25.0 to 29.9) and obese (BMI, 30.0 to 39.9) groups.

Compared with normal weight, overweight middle-aged men had a hazard ratio for incident CVD of 1.21; for overweight women, the hazard ratio was 1.32. Obese men had a hazard ratio for CVD of 1.67, and the corresponding figure for obese women was 1.85.

The researchers found the strongest association between BMI categories and heart failure (HF) compared with other subtypes of CVD, with a fivefold increase in incident HF in middle-aged men with morbid obesity, which they say "has particularly important implications for focusing on weight management strategies for HF prevention."

In terms of lifespan, normal weight middle-aged men lived 1.9 years longer than obese men and 6 years longer than those who were morbidly obese. Normal-weight men had longevity similar to that of overweight men. Normal-weight middle-aged women lived 1.4 years longer than overweight women, 3.4 years longer than obese women, and 6 years longer than morbidly obese women.

The researchers point out that "our findings suggest that earlier occurrence of CVD in those with obesity is most strongly associated with a greater proportion of life lived with CVD and shorter overall survival in adults aged 20 to 59 years at baseline."

Authors conclude that results provide critical perspective on the cardiovascular disease burden associated with overweight, highlight unhealthy years lived with increased cardiovascular morbidity, and challenge the prevalent view that overweight is associated with greater longevity compared with normal BMI.