Space & Innovation

Could Body Mass Index Predict How Long You'll Live?

Having a BMI in the overweight range may be linked with the lowest risk of dying, new research suggests.

Body mass index (BMI) is a common measure of body fat, but new research shows that having a BMI in the "normal weight" range is not always the healthiest for every person. In fact, for many people, having a BMI in the overweight range may be linked with the lowest risk of dying over a 13-year period, the research suggests.

Researchers looked at data on about 400,000 people in the U.S. who were ages 50 to 71 at the start of the study, in 1995. The researchers followed up with them through 2009, and about 112,000 people in the study had died by then. The findings showed that the "best" BMI for the people in the study in terms of their lifespan was 26, on average.

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A person's BMI is calculated based on their height and weight. Usually, a BMI below 18.5 is considered underweight, from 18.5 to 24.9 is considered normal weight, from 25 to 29.9 is considered overweight, and 30 and over is considered obese.

But these categories lump together people who actually have quite different BMIs, said study author Howard Karloff, a computer scientist formerly with Yahoo Labs and AT&T Labs, who worked on the new study because of his expertise in crunching large sets of data with numerous interacting variables. In the usual BMI categories, people with body weights that differ by 20 percent may be grouped together, Karloff said. [9 Healthy Habits You Can Do in 1 Minute (Or Less)]

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Previous studies have suggested that BMI is not a perfect way to measure a person's health. For example, researchers reported in 2015 that colorectal cancer patients with a BMI higher than 25 lived longer than those with a BMI under 25. Another study, published in 2011, showed that people with a BMI of 26 to 29 were more likely to survive after having surgery than people with a BMI of 23 or less.

In the new study, the researchers examined how BMI might relate to people's risk of dying. But instead of considering people's BMIs in the usual categories (of normal weight, overweight and so on), the researchers used the individuals' BMI numbers.

For each person in the study, the researchers looked at a dozen factors that could influence their risk of dying during a given period, including their age, race, education level, alcohol consumption, marital status and exercise level. The researchers calculated each person's "personalized optimal BMI," which is the BMI that, based on these variables, would be associated with the lowest relative risk of death for that person.

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The findings showed that any individual's "optimal" BMI depends on his or her own features, and that a "one-size-fits-all" recommendation about what BMI people should strive for may not be best, Karloff said.

"We were able to generate personalized recommendations that, according to our model ... are more accurate than the uniform recommendations given by the CDC [Centers for Disease Control and Prevention]," Karloff told Live Science.

Dr. Rexford Ahima, a professor of medicine at the University of Pennsylvania Perelman School of Medicine who was not involved in the study, said that"Body mass allows to compare relative weights of people across populations, but was never intended to be used as a healthy tool."

A person's BMI is "just a measure of fatness," Ahima told Live Science. "It says nothing about your risk of developing any disease or dying."

The study was published online Jan. 8 in the journal Obesity.

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Article first appeared on LiveScience.

June 28, 2012 --

Today the Supreme Court upheld the 2010 health care law in a dramatic victory for President Barack Obama. The lead up to today's decision has prompted debate between opponents and supporters of the Patient Protection and Affordable Care Act two years ago. Take a look at how we got to the health care system we have in place today.

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Prior to the 20th century, nothing even close to what could be called a health care system existed in the United States. Although the Civil War had led to some medical breakthroughs in terms of surgical techniques and pain management, medical knowledge, techniques and treatment availability at the time left little hope that patients would actually recover from severe ailments. As NPR's Alex Blumberg and Adam Davidson point out, medical treatments may have been downright medieval at the time, consisting of potions. But at least it was cheap. "In 1900, the average American spent $5 a year on health care ($100 in today's money)," they note in their report.

How the Civil War Changed Modern Medicine

In 1912, Theodore Roosevelt was the first presidential candidate to get behind the idea of a national health insurance plan. Roosevelt ultimately didn't win election that year. Proponents of government-provided health care tried to press the issue through state initiatives, only to see their efforts fail in 16 states. Roosevelt's plan may have certainly been ahead of its time, particularly since there weren't that many services that doctors could actually provide patients during that era.

At the same time, however, developments within the medical community changed the face of the industry. The horrors of World War I led to advances in the areas of wound care, sanitation, pain management and more, according to an article published in the Journal of the Royal Society of Medicine. Hospitals in the United States began to widely adopt the practice of using antiseptics to sanitize their facilities, preventing the possibility of medical personnel or patients becoming exposed to infection. That decade also saw the introduction of the first employer group insurance contracts (though not specifically for health insurance) as well as the first physician service and industrial health plans.

In 1928, Alexander Fleming made one of the most important discoveries in the history of medicine: penicillin, a life-saving drug used to treat countless millions. It would be decades, however, before penicillin would be mass-produced. Fleming's discovery was the signature achievement in an era that saw medical treatment become more effective, and, as a result, expensive. The Great Depression also fueled concerns about affordability of medical treatment as millions of Americans suddenly found themselves out of work. In 1929, Baylor Hospital provided the first group health insurance plan in the United States through an agreement with Dallas-area teachers. The plan was the forerunner of Blue Cross. The effort wasn't just meant to be in the best interests of patients, but also the hospitals. Patient facilities saw more empty beds as fewer patients during the Great Depression could afford treatment without participating in these collective prepaid health insurance plans.

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As part of his push to create a social safety net for Americans during the Great Depression, President Franklin D. Roosevelt advocated the passage of national health insurance. Roosevelt pushed ahead with efforts to pass Social Security first, a bill which intentionally omitted any mention of medical care to ensure its passage. Harry Truman attempted to carry on Roosevelt's legacy in 1945 by calling on Congress to create such a program. His efforts failed, partly due to criticism by the American Medical Association (AMA), who called the plan "socialized medicine." In this photo taken in 1937, First Lady Eleanor Roosevelt examines a chart of enrollment of health care insurance plans.

Like its predecessor, World War II would lead to new medical advancements, including the widespread adoption of antibiotics and the use of ultrasound. The war would also have a similar effect in terms of the spread of employer-sponsored health plans. Because the nation was in a state of emergency and had a legally mandated wage freeze as a result, employers had to attract workers to assist the war effort by providing them with benefits, including health insurance. Tax laws passed between 1943 and 1945 also gave breaks to employers who provided insurance to their employees, which gave businesses all the more incentive to offer coverage. Following the war, employer-sponsored health insurance became common. In 1951, around 77 million Americans had some kind of coverage, according to an insurance industry trade group. That era also saw one of the most celebrated medical achievements in history: Jonas Salk's polio vaccine.

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Although health insurance was widely available to employed Americans in the mid-20th century, the unemployed and the elderly were often excluded from these plans. President John F. Kennedy campaigned on the issue of insuring these groups. President Lyndon B. Johnson succeeded where Kennedy left off, securing the passage of a bill through Congress creating Medicare and Medicaid. At the bill-signing ceremony, shown here, Johnson presented former president Truman with the nation's first Medicare card. Within the medical industry itself, an increasing number of doctors began specializing in certain fields of medicine rather than acting as general physicians. By 1960, more than two-thirds of doctors reported themselves as full-time specialists, rather than general practitioners.

Starting with Richard Nixon in 1970, presidents have offered successive plans for covering the nation's uninsured, but they have have stalled for different reasons. In 1974, Nixon put forward a plan to cover all Americans through private insurance, only to have the Watergate scandal force him out of office. An economic crisis prevented Jimmy Carter from pushing forward with a national health plan. Congress late in Reagan's second term attempted to expand Medicare, only to have the law repealed the following year. Bill Clinton had a 1,300-page health care reform bill that was never even taken up for a vote in Congress. Since Nixon's presidency, health care costs have continued to rise, often outpacing inflation. This increase is due to a number of factors, including the increased use of new medical technologies for diagnosis and treatment. The Patient Protection and Affordable Care Act signed by President Barack Obama was intended to cover the 30 million Americans who live without health insurance, according to the bill's authors. It has been the most far-reaching piece of health care legislation since Johnson's signed the legislation creating the Medicare and Medicaid health care programs.

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