Scientists accept that obesity can shorten a person's life span, but they have debated whether being overweight, the weight category between normal and obese, is also a health risk.
The World Health Organization states that more than 1.9 billion people -- about 39 percent of adults -- are overweight, defined as having a body mass index between 25 and 30. For example, a 5-foot-4 person who weighs 140 pounds has a healthy BMI of 24. Add five pounds and this individual would be considered overweight.
The new research, a four-continent effort involving 239 studies and data from 10.6 million people, is one of the largest studies to date.
The study analyzed participants who had never smoked, did not have chronic disease and were still alive five years after the research began. The study involved 385,879 deaths in 239 studies.
Overweight and obesity were strongly connected to coronary heart disease, stroke and respiratory disease death, and were moderately linked to cancer mortality. The findings were reflected in Europe, North America and East Asia.
The new results on overweight should be strong motivation for people to return to a healthy weight, the study authors stated.
Being underweight, according to the study, was associated with substantially higher respiratory disease mortality and somewhat higher death rates from coronary heart disease, stroke and cancer. These findings held true in Asia, Australia, New Zealand, Europe and North America.
The WHO states that about 95 million children -- mostly in less developed regions -- are underweight.
One of the study's limitations, like many other research papers in this arena, is the use of BMI as a surrogate for abdominal fat, which is thought play a central role in bringing about the negative consequences linked to obesity.
Using an accepted but imperfect measure, the study was able to find a connection between premature death and being overweight. The proportion of premature deaths that could be avoided with a healthy weight (between BMI 18.5 and 25) is about 1 in 5 in North America, 1 in 6 in Australia and New Zealand, 1 in 7 in Europe and 1 in 20 in East Asia.
In short, like smoking, the health problems associated with underweight, overweight and obesity are substantial but potentially preventable.
Source: The Lancet, July 13, 2016.
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