'Obesity paradox' debunked

A new study debunks the "obesity paradox," a counterintuitive finding that showed people who have been diagnosed with cardiovascular disease live longer if they are overweight or obese compared with people who are normal weight at the time of diagnosis.

Obese people live shorter lives and have a greater proportion of life with cardiovascular disease, reports a new Northwestern Medicine study.

The paper will be published Feb. 28 in JAMA Cardiology.

The new study shows similar longevity between normal weight and overweight people, but a higher risk for those who are overweight of developing cardiovascular disease during their lifespan and more years spent with cardiovascular disease.

This is the first study to provide a lifespan perspective on the risks of developing cardiovascular disease and dying after a diagnosis of cardiovascular disease for normal weight, overweight and obese individuals.

"The obesity paradox caused a lot of confusion and potential damage because we know there are cardiovascular and non-cardiovascular risks associated with obesity," said Dr. Sadiya Khan, an assistant professor of medicine at Northwestern University Feinberg School of Medicine and a Northwestern Medicine cardiologist.

"I get a lot of patients who ask, 'Why do I need to lose weight, if research says I'm going to live longer?''' Khan said. "I tell them losing weight doesn't just reduce the risk of developing heart disease, but other diseases like cancer. Our data show you will live longer and healthier at a normal weight."

Obesity is defined as having a Body Mass Index (BMI) of 30 to 39.9; overweight is 25 to 29.9. BMI is a person's weight divided by the square of his or her height. An overweight individual, who is 5'4" and weighs 160 pounds, for example, would be considered overweight; a 5'4" person who weights 190 pounds is considered obese.

Higher odds of a stroke, heart attack, heart failure or dying from heart disease, according to the study:

• The likelihood of having a stroke, heart attack, heart failure or cardiovascular death in overweight middle-aged men 40 to 59 years old was 21 percent higher than in normal weight men. The odds were 32 percent higher in overweight women than normal weight women.
• The likelihood of having a stroke, heart attack, heart failure or cardiovascular death in obese middle-aged men 40 to 59 years old was 67 percent higher than in normal weight men. The odds were 85 percent higher in obese women than normal weight women.
• Normal weight middle-aged men also lived 1.9 years longer than obese men and six years longer than morbidly obese. Normal weight men had similar longevity to overweight men.
• Normal weight middle-aged women lived 1.4 years longer than overweight women, 3.4 years longer than obese women and six years longer than morbidly obese women.

"A healthy weight promotes healthy longevity or longer healthspan in addition to lifespan, so that greater years lived are also healthier years lived," Khan said. "It's about having a much better quality of life."

The study examined 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 cardiovascular disease at baseline and had objectively measured height and weight to assess BMI. Over follow-up, researchers assessed for cardiovascular disease overall and by type, including coronary heart disease, stroke, heart failure and cardiovascular death, as well as non-cardiovascular death.

Other Northwestern authors include Dr. Donald Lloyd-Jones, senior author, and co-authors Dr. Hongyan Ning, Dr. John T. Wilkins, Norrina Allen, Mercedes Carnethon, and Dr. Ranya N. Sweis.

The study was supported by grants R21 HL085375 F32 HL129695 from the National Institutes of Health/National Heart, Lung, and Blood Institute.