There are several studies that show that obese people are likely to outlive normal weight individuals. This is called the “obesity paradox” and researchers have tried to understand the reasons behind this. A new study disproves this theory and finds that obese and overweight people do not live longer than people who have a healthy body weight.
The study titled, “Association of Body Mass Index With Lifetime Risk of Cardiovascular Disease and Compression of Morbidity” was published yesterday (28th of February 2018) in the latest issue of the journal JAMA Cardiology.
The obesity paradox states that people who are overweight or obese and diagnosed with cardiovascular disease tend to live longer. This new study shows that overweight and obese people are diagnosed with heart disease at younger ages and they tend to live for a longer period of time with heart disease than normal weight individuals. Thus the number of years lived disease-free is much less among those who weigh more finds this study.
Dr. Sadiya Khan of Northwestern University's Feinberg School of Medicine and her team looked at data from Cardiovascular Disease Lifetime Risk Pooling Project and gathered information about 190,672 Americans free of cardiovascular disease at the start of the study. Their BMI or body mass index was recorded at least once and they were all followed up and tracked for 10 years providing the researchers with 3.2 million years of health data. A BMI of 25 to 29.9 is deemed overweight, that between 30 and 39.9 is obese and 40 or above is called morbid obesity. Next the team classified these individuals according to their age and weight.
They then noted that among people aged between 40 and 59 years, the overweight and obese individuals had a greater risk of getting heart attacks, stroke and congestive heart failure compared to those who had a healthy body weight. They found that among men of this age group 37% of those who were overweight, 47% of those who were obese and 65.4% of those who were morbidly obese developed some form of cardiovascular disease and related event during their follow up. In comparison, 32 percent men of same age with normal BMI suffered a cardiovascular event. Similarly for women of the same age, 27.9 percent overweight women, 38.8 percent obese women and 47.6 percent morbidly obese women developed a stroke, heart attack or heart failure during the study. The numbers were 21.5 percent among women with normal weight in the same age group.
The researchers then used statistics to account for various risk factors such as race, ethnicity, smoking status, age etc. and noted that higher BMI was still associated with a greater risk of cardiovascular events. Among middle aged men for example, the risk of heart attack was 18 percent higher for overweight men, 42 percent higher for obese men and 98 percent higher for morbidly obese men when compared to normal weight men. Similarly for women the risk was 42 percent for overweight, 75 percent for obese and 80 percent higher for morbidly obese women respectively compared to healthy weight women.
The most important finding from this study was that normal weight among middle aged adults lead to longer disease-free years of life. Morbidly obese men and women have a cardiovascular event 7.5 years and 7.1 years earlier than normal weight individuals respectively. Further middle aged men and women with normal body weights live 5.6 years and 2 years longer than morbidly obese men and women respectively. These numbers corroborate among younger and older populations as well.
The researchers write, “The obesity paradox … appears largely to be caused by earlier diagnosis of CVD (Cardiovascular disease)… Adults who were obese had an earlier onset of incident CVD, a greater proportion of life lived with CVD morbidity (unhealthy life years), and shorter overall survival compared with adults with normal BMI.” They concluded, “…obesity was associated with shorter longevity and significantly increased risk of cardiovascular morbidity and mortality compared with normal BMI.”