Differences In Muscle Mass May Explain The Obesity Paradox

A new study offers insight into the so-called 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, a new Northwestern Medicine study indicates.

The new research 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.

Lifespan Perspective

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. I get a lot of patients who ask, ‘Why do I need to lose weight, if research says I’m going to live longer?’ 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,”

said Dr. Sadiya Khan, an assistant professor of medicine at Northwestern University Feinberg School of Medicine and a Northwestern Medicine cardiologist.

Higher Risks For The Obese

 Risk of mortality by BMI category and muscle mass status, without and with adjustment for waist circumference.

Risk of mortality by BMI category and muscle mass status, without and with adjustment for waist circumference.
Credit: Abramowitz et al. CC-BY

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.

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 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.

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

Khan said.

No Healthy Obesity

Another new paper is calling for an end to the term “healthy obesity”, due to it being misleading and flawed. The focus should instead be on conducting more in-depth research to understand causes and consequences of varying health among people with the same BMI.

The term healthy obesity was first used in the 1980’s to describe obese individuals who were apparently healthy — for example they didn’t suffer with hypertension or diabetes.

Dr William Johnson, from the School of Sport, Exercise and Health Sciences at Loughborough University, emphasizes in the article that the construct of healthy obesity is limited. This is because categorizing a population using cut-offs (e.g., BMI > 30 kg/m2 and blood pressure < 140/90 mmHg) results in some normal weight and obese individuals being labelled healthy, when there are obviously health differences between the two groups.

“While the concept of healthy obesity is crude and problematic and may best be laid to rest, there is great opportunity for human biological investigation of the levels, causes, and consequences of heterogeneity in health among people with the same BMI,”

Johnson said.

With obesity at epidemic levels worldwide, such research could inform the development of more stratified disease prevention and intervention efforts targeted at individuals who have the highest risk.

Abramowitz MK, Hall CB, Amodu A, Sharma D, Androga L, Hawkins M
Muscle mass, BMI, and mortality among adults in the United States: A population-based cohort study
PLoS ONE 13(4): e0194697. https://doi.org/10.1371/journal.pone.0194697

William Johnson
Healthy obesity: time to give up the ghost?
Annals of Human Biology DOI: 10.1080/03014460.2018.1444789

Top Image: Sergio Bertazzo, Department of Materials, Imperial College London. CC BY. Density-dependent colour scanning electron micrograph of the surface of human heart (mitral valve) tissue displaying calcification in the form of spherical particles.