As overweight and obesity increase, so does risk of dying prematurely

July 13, 2016

Being overweight or obese is associated with a higher risk of dying prematurely than being normal weight—and the risk increases with additional pounds, according to a large international collaborative study led by researchers at the Harvard T.H. Chan School of Public Health and the University of Cambridge, UK. The findings contradict recent reports that suggest a survival advantage to being overweight—the so-called "obesity paradox."

The study will be published online on July 13, 2016 in The Lancet.

The of on chronic disease have been well documented. Recent studies suggesting otherwise have resulted in confusion among the public about what is a healthy weight. According to the authors of the new study, those prior studies had serious methodological limitations. One common problem is called reverse causation, in which a low is the result of underlying or preclinical illness rather than the cause. Another problem is confounding by smoking because smokers tend to weigh less than nonsmokers but have much higher mortality rates. "To obtain an unbiased relationship between BMI and mortality, it is essential to analyze individuals who never smoked and had no existing chronic diseases at the start of the study," said Frank Hu, professor of nutrition and epidemiology at Harvard Chan School and a co-leader of the collaboration. Hu stressed that doctors should continue to counsel patients regarding the deleterious effects of excess body weight, which include a higher risk of diabetes, cardiovascular disease, and cancer.

In order to provide more definitive evidence for the association of excess body weight with , researchers joined forces in 2013 to establish the Global BMI Mortality Collaboration, which involves over 500 investigators from over 300 global institutions.

"This international collaboration represents the largest and most rigorous effort so far to resolve the controversy regarding BMI and mortality," said Shilpa Bhupathiraju, research scientist in the Department of Nutrition at Harvard Chan School and co-lead author of the study.

For the new study, consortium researchers looked at data from more than 10.6 million participants from 239 large studies, conducted between 1970 and 2015, in 32 countries. A combined 1.6 million deaths were recorded across these studies, in which participants were followed for an average of 14 years. For the primary analyses, to address potential biases caused by smoking and preexisting diseases, the researchers excluded participants who were current or former smokers, those who had at the beginning of the study, and any who died in the first five years of follow-up, so that the group they analyzed included 4 million adults. They looked at participants' (BMI)—an indicator of body fat calculated by dividing a person's weight in kilograms by their height in meters squared (kg/m2).

The results showed that participants with BMI of 22.5-<25 kg/m2 (considered a healthy weight range) had the lowest mortality risk during the time they were followed. The risk of mortality increased significantly throughout the overweight range: a BMI of 25-<27.5 kg/m2 was associated with a 7% higher risk of mortality; a BMI of 27.5-<30 kg/m2 was associated with a 20% higher risk; a BMI of 30.0-<35.0 kg/m2 was associated with a 45% higher risk; a BMI of 35.0-<40.0 kg/m2 was associated with a 94% higher risk; and a BMI of 40.0-<60.0 kg/m2 was associated with a nearly three-fold risk. Every 5 units higher BMI above 25 kg/m2 was associated with about 31% higher risk of premature death. Participants who were underweight also had a higher mortality risk.

Looking at specific causes of death, the study found that, for each 5-unit increase in BMI above 25 kg/m2, the corresponding increases in risk were 49% for cardiovascular mortality, 38% for respiratory disease mortality, and 19% for cancer mortality. Researchers also found that the hazards of excess body weight were greater in younger than in older people and in men than in women.

Explore further: No evidence of survival advantage for type 2 diabetes patients who are overweight or obese

Related Stories

No evidence of survival advantage for type 2 diabetes patients who are overweight or obese

January 15, 2014
Being overweight or obese does not lead to improved survival among patients with type 2 diabetes. The large-scale study led by Harvard School of Public Health (HSPH) researchers refutes previous studies that have suggested ...

Obesity less dangerous than 40 years ago

May 10, 2016
New research from Denmark involving more than 100,000 individuals suggests that the excess risk of premature death associated with obesity has decreased over the past 40 years. All-cause mortality was higher in obese individuals ...

Heavy body shape across lifespan associated with highest mortality

May 4, 2016
People who are lean for life have the lowest mortality, while those with a heavy body shape from childhood up to middle age have the highest mortality, reveal findings of a large study published in The BMJ today.

Consuming probiotics promotes weight loss and reduces BMI

July 11, 2016
Consuming probiotics, so-called 'good bacteria', can reduce body weight and body mass index (BMI) according to a new meta-analysis published in the International Journal of Food Sciences and Nutrition.

Mortality risk of overweight and obesity similar for blacks, whites

October 8, 2014
A study from American Cancer Society researchers finds the increased risk of premature death associated with a higher body mass index (BMI) is similar for African Americans and whites, in contrast to previous, smaller studies ...

Low BMI and death after heart attack

April 19, 2016
Low body mass index increases risk mortality after acute myocardial infarction (AMI), even after adjustment for other health factors that affect body weight, according to a study this week in PLOS Medicine. Emily Bucholz, ...

Recommended for you

'Obesity paradox' not found when measuring new cases of cardiovascular disease

December 7, 2017
Although obesity is a well-known risk factor for getting cardiovascular disease, a controversial body of research suggests that obesity may actually be associated with improved survival among people who have cardiovascular ...

Harmful effects of being overweight underestimated

December 1, 2017
The harmful effects of being overweight have been underestimated, according to a new study that analysed body mass index (BMI), health and mortality data in around 60,000 parents and their children, to establish how obesity ...

More than half of US children will have obesity as adults if current trends continue

November 29, 2017
If current trends in child obesity continue, more than 57% of today's children in the U.S. will have obesity at age 35, according to a new study from Harvard T.H. Chan School of Public Health.

Exercise alone does not lead to weight loss in women—in the medium term

November 23, 2017
Knowing whether or not exercise causes people to lose weight is tricky. When people take up exercise, they often restrict their diet – consciously or unconsciously – and this can mask the effects of the exercise. In our ...

Mindfulness training shows promise for maintaining weight loss

November 23, 2017
Can mindfulness training help overweight people shed pounds and keep them off? McGill University researchers surveyed the growing body of studies investigating that question, and came away encouraged.

Shaming overweight kids only makes things worse

November 20, 2017
(HealthDay)—Overweight kids who are shamed or stigmatized are more likely to binge eat or isolate themselves than to make positive changes such as losing weight, a leading pediatricians' group says.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.