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The Idea of 'Healthy Obesity' is Misleading and Risky, Study Shows

The Idea of 'Healthy Obesity' is Misleading and Risky, Study Shows

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By the end of the study, approximately half of the obese adults had metabolic indicators of poor health.

A new study published in the Journal of The American College of Cardiology suggests that, contrary to the “intense interest” surrounding the concept of “healthy” obesity, those who are obese are nearly eight times more likely to “progress to an unhealthy obese state after 20 years than healthy non-obese adults.”

Healthy obesity, therefore — defined as “obesity in the absence of metabolic risk factor clustering,” such as high cholesterol, blood pressure, and insulin resistance — was found to last only a short while before the subjects transitioned.

Out of 2,521 subjects profiled during the study, 66 were obese adults who were identified as being in good health at the start of research. By the end of the study two decades later, 51 percent of the healthy obese subjects were unhealthy, defined by poor results in two or more of the measures of metabolic health: cholesterol, triglycerides, blood pressure, fasting glucose levels and insulin resistance. Only 10 percent had become healthily non-obese.

“‘Healthy obesity’ is quite a misleading term,” Joshua A. Bell, a doctoral candidate at University College London and the paper’s lead author, told The New York Times.

“It sounds safe, but we know that it’s only healthy in a relative sense. The healthy obese become unhealthy and progress into the highest risk group. This is a real challenge to the idea that the obese can be healthy in the long term.”

If Obesity Is a Disease, Why Are So Many Obese People Healthy?


The decision of the American Medical Association (AMA) to classify obesity as a disease is great news for the pharmaceutical industry, as it is likely to increase pressure on the Food and Drug Administration to approve more weight-loss drugs and increase the odds that insurance companies will reimburse their cost. But it is deeply misleading.

Treating obesity as a disease implies that moving into the category of obesity, which for adults means moving from a body-mass index (BMI) of 29 to a BMI of 30, is equivalent to contracting a disease. But that is simply not the case.

Yes, there are certain health risks associated with having an elevated BMI, such as type 2 diabetes and heart disease. More broadly, a higher BMI is associated with a greater risk of cardiometabolic abnormalities, as measured by blood pressure, triglycerides, cholesterol, glucose, insulin resistance and inflammation. Nonetheless, almost one quarter of “normal weight” people also have metabolic abnormalities, and more than half of “overweight” and almost one third of “obese” people have normal profiles, according to a 2008 study. That’s 16 million normal-weight Americans who have metabolic abnormalities and 20 million obese (or 56 million overweight and obese) Americans who have no such abnormalities.

One explanation for this discrepancy is that physical fitness and/or nutrition — rather than weight per se — may be what really matters. Several studies have shown that physically fit “obese” individuals have lower incidence of heart disease and mortality from all causes than do sedentary people of “normal” weight. A recent clinical trial published in the New England Journal of Medicine showed that adopting a Mediterranean diet reduced cardiovascular risk independent of weight loss.

Some assume that the problem lies with BMI as a measure, which does not distinguish between fat, muscle and bone. While BMI is indeed a flawed measure, it is not clear that there are better ones. A 2009 study, using the National Health and Nutrition Examination Survey, estimated excess deaths for people of standard BMI levels as well as for those with comparable levels of percentage body fat, waist circumference, hip and arm circumferences, waist-to-hip ratio, the sum of four skinfold thicknesses and waist-to-stature ratio. They found no systematic differences between BMI and other variables. In other words, it is not just that BMI is a poor measure of obesity but that obesity is a poor predictor of health.

Some hope that designating obesity as a disease will remove the stigma associated with it, and obese people will no longer be blamed for their condition. Yet already it is being called the “fork to mouth” disease, and the disease categorization may reinforce blame by raising the stakes. If obesity is a disease, parents of fat children may not merely be silently judged as bad parents but also accused of neglect and child endangerment.

If the AMA’s goal is to address the serious diseases of type 2 diabetes and heart disease, it would be more productive and accurate for the association to urge doctors to focus on cardiometabolic risk, recognizing that there are both metabolically healthy and metabolically unhealthy individuals in all categories of weight. Rather than promote weight loss per se, doctors should instead encourage their patients of all sizes to incorporate physical activity and a balanced diet into their lives.

Abigail C. Saguy

Abigail C. Saguy is an Associate Professor of Sociology and of Gender Studies at UCLA. She is the author of What’s Wrong With Fat? and What Is Sexual Harassment? From Capitol Hill to the Sorbonne. The views expressed are solely her own.

Studies saying fat is not that bad are misleading, scientists say

A scientific study suggesting that eating a lot of fat may not be so bad for you is misleading, and if you want to eat cake you should do it like Mary Berry and opt for a smaller slice, according to nutrition scientists.

Saturated fats in foods such as meat, cakes and butter are still bad for your heart, in spite of headlines apparently giving them a clean bill of health earlier this year. Those reports were based on a study by Dr Rajiv Chowdhury of Cambridge University published in March.

The Cambridge team suggested that polyunsaturated fats in fish and olive oils were not necessarily better for us after all, overturning the assumptions of decades. They concluded that dietary guidelines might need to be rethought.

Widespread coverage of the March study in UK newspapers has led to uncertainty and confusion, the nutrition scientists said. What received less publicity were the corrections to the articles which appeared in the Annals of Internal Medicine, although the authors said they did not change the conclusions.

Berry, judge of The Great British Bake Off, “cooks cakes which everyone would think are awful (for your health),” said Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London yesterday. “But [Berry] says, ‘I only eat a little bit’.”

Christine Williams, professor of human nutrition at Reading University, told of the difficulty in comparing the findings from more than 70 studies Chowdhury and colleagues pulled together for their meta-analysis. Dietary studies are notoriously problematic, because people who take part forget or deliberately omit to mention foods they are eating that they know are supposed to be bad for them. “About 60% [of people] when asked what they eat systematically under-report by 20-30% their energy [intake],” she said. “Overweight people are more likely to do so than underweight people.”

Studies also only ask what people have eaten at one point – maybe a day or a week – and then make assumptions for years to come, she said.

Scientific experiments in animals and people have shown that diets high in saturated fats lead to high levels of “bad” of LDL cholesterol in the blood, which stick to the walls of the arteries and clog them, sometimes leading to heart attacks and stroke, said Prof Andy Salter, head of nutritional sciences at the University of Nottingham.

All saturated fatty acids are not equal, he said – some raise levels of “good” HDL cholesterol as well as bad. Studies had also sometimes found that people who ate a lot of saturated fat also had less active lifestyles and were more likely to smoke, so the picture was complicated, he acknowledged.

Since the 1960s there has been a big drop in the amount of whole milk, butter and beef we consume, but people are no better off if they replace saturated fat with refined carbohydrates, said Sanders. Unrefined carbohydrates, such as whole grains, are good, but refined carbohydrates, including sugars, are not. Low fat yoghurts have been heavily laced with sugar, for instance, to make them taste better.

Obesity and type 2 diabetes are increasing, said Sanders. “Obesity is not about carbohydrate intake – body fat comes from dietary fat,” he said.

Snacking and portion size were at the heart of the problem, he said. A muffin on the way to work could be 600 calories. Washed down “with a nice latte”, he said, “that’s half your intake in a day”. Government guidelines suggest women need around 2,000 calories a day and men 2,500.

Salter said it was impossible for most people to monitor their saturated fat intake all the time. “You have to look at foods, not fats,” he said. “The advice is that two to three portions of red meat a week is probably OK and will give you some important nutrients.” Obesity is fuelled mostly by the foods eaten between meals, such as muffins, crisps, cakes and biscuits – all high in fat and made palatable by sugar, said the scientists.

“Eating fewer calories is the only effective way of losing weight,” Sanders said. “Smaller plates are useful – we have these Shrek-sized bowls. We have got used to bigger and bigger portions.”

The good news is that you can take steps to lose weight. And losing even some weight can make a big difference to your health and how you feel. You may not have to lose as much as you might think in order to start seeing health benefits.

As a start, aim to lose 1-2 pounds a week. Adults who are overweight or obese should try to lose 5% to 10% of their current weight over 6 months, according to the National Heart, Lung, and Blood Institute.

If you're ready to get started with a weight loss program, ask your doctor to help you set personal goals and refer you to other professionals who can give you tips and help you reach your goals. For example, a nutritionist can help you with a food plan, and a physical therapist or trainer can help you move more.

You’ll want to go for steady progress over time, and to make lifestyle changes that work for you for the long run. That way you can start losing weight and feel better.


Stanford Hospital & Clinics: "Health Effects of Obesity."

National Heart, Lung, and Blood Institute: "What Are the Health Risks of Overweight and Obesity?" and "How Are Overweight and Obesity Treated?"

What's "healthy" depends in part on your race and ethnic background

The real kicker, though, is that the BMI system, originally known as the Quetelet Index, stems from decades of research that&rsquos been mainly focused on white people. While BMI math is calculated the same way for everyone, research shows the meaning of the resulting number changes depending on your ethnicity.

&ldquoThe Indian population, for example, we know that their chances of metabolic syndrome like diabetes and heart disease go up at a BMI of 27,&rdquo says Dr. Majid. That&rsquos lower than the BMI of 30 that&rsquos associated with the same health issues in Caucasian people. The number is even lower for people of Taiwanese descent, adds Dr. Majid. That means someone might think they&rsquore in the clear with a BMI that&rsquos less than 30 and actually be at serious risk for health issues.

Another potential problem is that if physicians aren&rsquot familiar with these differences between ethnic backgrounds, they might miss an opportunity to give life-saving care to someone they mistakenly believe is metabolically healthy.

New Study Says You Can’t Be Overweight and Healthy

We all love our sports, and great athletes come in all different shapes and sizes. From lean swimmers and long-distance runners to beefy football players and even sumo wrestlers, the notion that you can be obese but fit is an idea accepted by many as fact, but research recently published in the European Journal of Preventive Cardiology says otherwise.

An extensive study conducted in Spain, using data collected from more than half a million working adults, with an average age of 42 years, sought to understand just what an individual’s body mass index (BMI) means to the likelihood of suffering diabetes, high blood pressure, or high cholesterol in those that exercise versus those who are inactive.

On the positive side, the results appear to show that as physical activity increases, the chances of diabetes and hypertension lowers, illustrating a favorable link between working out and improving overall health. However, those individuals who were overweight or obese still suffered from a greater risk of negative cardiovascular outcomes as opposed to both active and inactive people within their normal weight range. The research also showed that active, but obese, people were twice as likely to have higher cholesterol than inactive but normal weight individuals. On top of that, they were four times more likely to develop diabetes, and five times more likely to suffer high blood pressure.

“This was the first nationwide analysis to show that being regularly active is not likely to eliminate the detrimental health effects of excess body fat,” said study author, Dr. Alejandro Lucia of the European University in Madrid. “Our findings refute the notion that a physically active lifestyle can completely negate the deleterious effects of overweight and obesity”. The findings mean that although exercise will improve the health of an individual regardless of their weight, it is not possible to ignore excess body fat as a risk factor and try to compensate for it by becoming more active. The risk to health associated with obesity cannot be cancelled out.

“Fighting obesity and inactivity is equally important it should be a joint battle. Weight loss should remain a primary target for health policies together with promoting active lifestyles,” said Dr. Lucia. “One cannot be ‘fat but healthy.'”

Measuring Body Fat

One of the most widely used tools for calculating healthy weight estimates is the body mass index (or BMI for short), which relies on the ratio of weight to height measurements.

How to determine your body mass index:

  1. Divide your weight in pounds by your height in inches.
  2. Divide the answer by your height in inches.
  3. Multiply the answer by 703.

You can also use the National Heart, Lung and Blood Institute’s online BMI calculator or simple BMI tables.

Now that you know your BMI, what does it mean?

  • A healthy weight is one that equates with a body mass index of less than 25. Overweight is defined as a body mass index of 25 to 29.9, and obesity is defined as a body mass index of 30 or higher.

Dozens of studies have shown that a body mass index above 25 increases the chances of dying early.

  • A meta-analysis published in the New England Journal of Medicine focused on the relationship between BMI and mortality. (14) The study showed a clear relationship between BMI and mortality, with both underweight (BMI <18.5) and overweight and obese (BMI >25) BMIs causing an increase in mortality. The lowest death rate from any cause was associated with the BMI range between 22.5 and 24.9.
    • Experts believe that this study was strong because it was able to exclude smokers, individuals with cancer and heart disease, and individuals over the age of 85 who may be in the normal BMI range but may be suffering from frailty or other age-related unhealthy weight loss.
    • This meta-analysis also excluded participants who were current or former smokers, those who had chronic diseases at the beginning of the study, and any who died in the first five years of follow-up (a combined 1.6 million deaths were recorded across these studies where participants were followed for an average of 14 years).

    When examining the relationship between BMI and mortality, failure to adjust for these variables can lead to reverse causation (where a low body weight is the result of underlying illness, rather than the cause) or confounding by smoking (because smokers tend to weigh less than non smokers and have much higher mortality rates). Experts say these methodological flaws have led to paradoxical, misleading results that suggest a survival advantage to being overweight.

    Also note that muscle and bone are denser than fat, so an extremely muscular athlete may have a high body mass index, but may not actually be overweight or obese. This is not a problem for most athletic people, however.

    Read more about the BMI on the Obesity Prevention Source.

    Waist Size

    Not all fat is created equal. While overall body fat percentage is important, it’s especially important to monitor abdominal obesity (also called visceral fat), which may be more dangerous for long-term health than fat that accumulates around the hips and thighs (known as subcutaneous fat). (15)

    • Some studies suggest that abdominal fat plays a role in the development of insulin resistance and inflammation, an immune system response which has been implicated in heart disease, diabetes, and even some cancers.
    • The National Institutes of Health concluded that a waist larger than 40 inches for men and 35 inches for women increases the chances of developing heart disease, cancer, or other chronic diseases.

    Waist size is a simple, useful measurement because abdominal muscle can be replaced by fat with age, even though weight may remain the same. So, an increasing waist size can be an important “warning sign,” and should prompt you to examine how much you are eating and exercising.

    • Some believe that waist-to-hip ratio is a better indicator of risk, as waist size may vary based on body frame size, but one of the largest studies to date found that waist size and waist-to-hip ratio were equally effective at predicting risk of death from heart disease, cancer, or any cause.(16)

    In people who are not overweight, waist size may be an even more telling warning sign of increased health risks than BMI. (16)

    • The Nurses’ Health Study looked at the relationship between waist size and death from heart disease, cancer, or any cause in middle-aged women. At the start of the study, all 44,000 study volunteers were healthy, and all of them measured their waist size and hip size. After 16 years, women who had reported the highest waist sizes—35 inches or higher—had nearly double the risk of dying from heart disease, compared to women who had reported the lowest waist sizes (less than 28 inches). Women in the group with the largest waists had a similarly high risk of death from cancer or any cause, compared with women with the smallest waists. The risks increased steadily with every added inch around the waist.

    Even women at a “normal weight”—BMI less than 25—were at a higher risk, if they were carrying more of that weight around their waist: Normal-weight women with a waist of 35 inches or higher had three times the risk of death from heart disease, compared to normal-weight women whose waists were smaller than 35 inches.

    • The Shanghai Women’s Health study found a similar relationship between abdominal size and risk of death from any cause in normal-weight women. (17)

    Know your waist size – how to measure and assess:

    Wrap a flexible measuring tape around your midsection where the sides of your waist are the narrowest. This is usually even with your navel. Make sure you keep the tape parallel to the floor.

    • An expert panel convened by the National Institutes of Health concluded that a waist larger than 40 inches for men and 35 inches for women increases the chances of developing heart disease, cancer, or other chronic diseases. (18) Although these are generous guidelines, (19) they are useful benchmarks.


    14. Berrington de Gonzalez, A., et al., Body-mass index and mortality among 1.46 million white adults. N Engl J Med, 2010. 363(23): p. 2211-9.
    15. Willett W, Nutritional epidemiology. 1998, New York: Oxford University Press.
    16. Zhang, C., et al., Abdominal obesity and the risk of all-cause, cardiovascular, and cancer mortality: sixteen years of follow-up in US women. Circulation, 2008. 117(13): p. 1658-67.
    17. Zhang, X., et al., Abdominal adiposity and mortality in Chinese women. Arch Intern Med, 2007. 167(9): p. 886-92.
    18. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults–The Evidence Report. National Institutes of Health. Obes Res, 1998. 6 Suppl 2: p. 51S-209S.
    19. Willett, W.C., W.H. Dietz, and G.A. Colditz, Guidelines for healthy weight. N Engl J Med, 1999. 341(6): p. 427-34.
    20. Angelantonio, E. et al., Body-mass index and all-cause mortality: Individual-participant-data meta-analysis of 239 prospective studies in four continents. The Lancet. July 13, 2016.

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    The contents of this website are for educational purposes and are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The Nutrition Source does not recommend or endorse any products.

    The obesity paradox debunked: People with extra pounds do not live longer, study shows

    For several years, researchers have struggled to explain the obesity paradox. This is the observation that, after being diagnosed with cardiovascular disease, people who are overweight or obese live longer than people who have a healthy weight.

    How is it possible for those extra pounds to provide extra years of life? The answer, it turns out, is simple.

    A new study shows what’s really going on: People who are overweight or obese are being diagnosed with cardiovascular disease at younger ages. Although they do spend more years living with the disease than their slimmer peers, they do not live longer overall.

    Indeed, one of the main effects of carrying around too much excess weight is that you get fewer years of disease-free life.

    A team of researchers led by Dr. Sadiya Khan of Northwestern University’s Feinberg School of Medicine figured this out by examining data from the Cardiovascular Disease Lifetime Risk Pooling Project.

    They pulled medical information on 190,672 Americans who did not have cardiovascular disease when they began being tracked by researchers. All of them had their height and weight measured at least once, and all of them were followed for at least 10 years. Altogether, they provided researchers with 3.2 million years of health data.

    The researchers grouped the study participants according to their age and their weight status. Starting with people between the ages of 40 and 59, they saw that those who were overweight or obese had a higher risk of a heart attack, stroke or congestive heart failure than did those with a normal weight.

    For instance, among middle-aged men, 37% of those who were overweight (that is, with a body mass index between 25 and 29.9) experienced some type of cardiovascular event after joining a study. So did 47% of men who were obese (with a body mass index between 30 and 39.9) and 65.4% of those who were morbidly obese (with a BMI of 40 or above). By comparison, 32% of men with a BMI in the normal range (between 18.5 and 24.9) suffered a cardiovascular event.

    Among middle-aged women, 27.9% of those who were overweight had a heart attack, stroke or congestive heart failure after joining a study, as did 38.8% of those who were obese and 47.6% of those who were morbidly obese. Among women with a normal weight, 21.5% experienced one of these cardiovascular events.

    After adjusting the data to account for risk factors like age, race, ethnicity and smoking status, Khan and her colleagues found that the higher the BMI, the greater the lifetime risk of some type of heart problem. For example, compared to middle-aged men with a normal BMI, the risk of a heart attack (either fatal or nonfatal) was 18% higher for men who were overweight, 42% higher for men who were obese, and 98% higher for men who were morbidly obese.

    For middle-aged women, the risk of a heart attack was 42% higher for those who were overweight, 75% higher for those who were obese and 80% higher for those who were morbidly obese.

    The researchers found that middle-aged adults with a normal weight lived the most years free of cardiovascular disease. For instance, men who were morbidly obese experienced their first cardiovascular event 7.5 years sooner than men with a normal BMI. For women, the difference was 7.1 years.

    In addition, a normal weight was associated with a longer life overall. Middle-aged men with a normal BMI lived 5.6 years longer than men who were morbidly obese, while women with a normal BMI lived 2 years longer than women who were morbidly obese.

    All of these patterns were similar in younger and in older adults, the researchers found.

    By looking at people’s health over a longer period of time — not just after they’ve been diagnosed with a heart problem — the true significance of the obesity paradox comes into view.

    “The obesity paradox … appears largely to be caused by earlier diagnosis of CVD,” the researchers wrote, using an abbreviation for 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.

    The study was published Wednesday in the journal JAMA Cardiology.

    Follow me on Twitter @LATkarenkaplan and “like” Los Angeles Times Science & Health on Facebook.

    The information you've given us indicates you could be underweight.

    There can be health risks associated with a low BMI such as anaemia, osteoporosis, a weakened immune system and fertility problems.

    This is not a medical diagnostic tool so don't panic if this isn't the result you were expecting to see.

    If you're concerned about your weight, or your health in general, speak to a healthcare professional such as your GP.

    Follow the links for more information and advice on what to do if you're underweight:

    You're in the healthy range which is great. Research shows that having a healthy BMI can reduce your risk of serious health problems, such as type 2 diabetes, heart disease, stroke and some cancers.

    But not all people with a BMI in this range have a lower risk. Other factors such as smoking, high blood cholesterol or high blood pressure will increase your risk.

    If you're of Asian descent you have a higher risk of heart disease and diabetes at a lower BMI and waist circumference. A healthy BMI for you would be 18.5-23.

    We're more likely to gain weight as we get older so to stay a healthy weight you may need to make small changes to your diet or your activity levels as you age.

    Here are some tips to help you stay healthy:

    The information you've given us indicates you are overweight.

    Research shows that a BMI above the healthy range can increase your risk of serious health problems, such as type 2 diabetes, heart disease, stroke, and some cancers.

    A healthy BMI for a person of your height would be 18.5-24.9. If you're of Asian descent you have a higher risk of heart disease and diabetes at a lower BMI and waist circumference. A healthy BMI for you would be 18.5-23.

    Losing even a small amount of weight, if sustained, can have a big impact. For most people changing your diet is by far the best way to lose weight. Activity can help you maintain your target weight, and can have other health benefits, but increasing activity alone is not nearly as effective as diet at helping you shed the pounds.

    Even small changes like reducing portion sizes or choosing lower calorie snacks and drinks can help you lose weight or stop putting it on.

    Here are some other options you may want to try:

    The information you've given us indicates you're in the obese category.

    Research shows that having a BMI in this range will significantly increase your risk of serious health problems, such as type 2 diabetes, heart disease, stroke, and some cancers.

    A healthy BMI for a person of your height would be 18.5-24.9. If you're of Asian descent you have a higher risk of heart disease and diabetes at a lower BMI and waist circumference. A healthy BMI for you would be 18.5-23.

    Losing even a small amount of weight, if sustained, can have a big impact. For most people changing your diet is by far the best way to lose weight. Activity can help you maintain your target weight, and can have other health benefits, but increasing activity alone is not nearly as effective as diet at helping you shed the pounds.

    There's lots of support available to help you make changes, either to lose weight or to stop putting on weight.

    Here are some options you may want to try:

    The information you've given us indicates you're in the very obese category.

    Research shows that having a BMI in this range will significantly increase your risk of serious health problems, such as type 2 diabetes, heart disease, stroke, and some cancers.

    A healthy BMI for a person of your height would be 18.5-24.9. If you're of Asian descent you have a higher risk of heart disease and diabetes at a lower BMI and waist circumference. A healthy BMI for you would be 18.5-23.

    Losing even a small amount of weight, if sustained, can have a big impact. For most people changing your diet is by far the best way to lose weight. Activity can help you maintain your target weight, and can have other health benefits, but increasing activity alone is not nearly as effective as diet at helping you shed the pounds.

    If you are concerned, or would like to find out more, speak to your doctor or GP. If you are ready to make lifestyle changes, there is lots of support available.

    Here are some options you may want to try:

    Obesity spreads to friends, study concludes

    Obesity can spread from person to person, much like a virus, according to researchers. When one person gains weight, close friends tend to gain weight too.

    Their study, published Thursday in the New England Journal of Medicine, involved a detailed analysis of a large social network of 12,067 people who had been closely followed for 32 years, from 1971 until 2003. The investigators knew who was friends with whom, as well as who was a spouse or sibling or neighbor, and they knew how much each person weighed at various times over three decades.

    That let them watch what happened over the years as people became obese. Did their friends also become obese? Did family members? Or neighbors?

    The answer, the researchers report, was that people were most likely to become obese when a friend became obese. That increased one's chances of becoming obese by 57 percent.

    There was no effect when a neighbor gained or lost weight, however, and family members had less of an influence than friends. It did not even matter if the friend was hundreds of miles away - the influence remained. And the greatest influence of all was between mutual close friends. There, if one became obese, the other had a 171 percent increased chance of becoming obese too.

    The same effect seemed to occur for weight loss, the investigators say, but since most people were gaining, not losing, over the 32 years, the result was an obesity epidemic.

    Dr. Nicholas Christakis, a physician and professor of medical sociology at Harvard Medical School and a principal investigator in the new study, says one explanation is that friends affect each others' perception of fatness. When a close friend becomes obese, obesity may not look so bad.

    "You change your idea of what is an acceptable body type by looking at the people around you," Christakis said.

    The investigators say their findings can help explain why Americans became fatter in recent years: Persons who became obese were likely to drag some friends with them.

    Their analysis was unique, Christakis said, because it moved beyond a simple analysis of one person and his or her social contacts, and instead examined an entire social network at once, looking at how a friend's friends' friends, or a spouse's siblings' friends, could have an influence on a person's weight. The effects, Christakis said, "highlight the importance of a spreading process, a kind of social contagion, that spreads through the network."

    Of course, the investigators say, social networks are not the only factors that affect body weight. There is a strong genetic component at work too.

    Science has shown that individuals have genetically determined ranges of weights, spanning perhaps 30 or so pounds, or 13.5 kilograms, for each person. But that leaves a large role for the environment in determining whether a person's weight is near the top of his or her range or near the bottom. As people have gotten fatter, it appears that many are edging toward the top of their ranges. The question has been why.

    If the new research is correct, it might mean that something in the environment seeded what many call an obesity epidemic, making a few people gain weight. Then social networks let the obesity spread rapidly.

    It also might mean that the way to avoid becoming fat is to avoid having fat friends.

    That is not the message they meant to convey, say the study investigators, Christakis and his colleague James Fowler, an associate professor of political science at the University of California in San Diego. You don't want to lose a friend who becomes obese, Christakis said. Friends are good for your overall health, he explains.

    So why not make friends with a thin person, he suggests, and let the thin person's behavior influence you and your obese friend?

    That answer does not satisfy obesity researchers like Kelly Brownell, director of the Rudd Center for Food Policy and Obesity at Yale University.

    "I think there's a great risk here in blaming obese people even more for things that are caused by a terrible environment," Brownell said.

    On average, the investigators said, their rough calculations show that a person who became obese gained 17 pounds, and the newly obese person's friend gained 5 pounds. But some gained less or did not gain at all, while others gained much more.

    Those extra pounds were added onto the natural increases in weight that occur when people get older. What usually happened was that peoples' weights got high enough to push them over the boundary, a body mass index of 30, that divides overweight and obese. (For example, a man 6 feet, or 1.8 meters, tall who went from 220 pounds to 225 would go from being overweight to obese.)

    While other researchers were surprised by the findings, the big surprise for Christakis was that he could do the study at all. He got the idea for it from all the talk of an obesity epidemic.

    "One day I said, 'Maybe it really is an epidemic. Maybe it spreads from person to person,' " Christakis recalled.

    It was only by chance that he discovered a way to find out. He learned that the data he needed were contained in a large U.S. federal study of heart disease that had followed the population of Framingham, Massachusetts, for decades, keeping track of nearly every one of its participants.

    The study's records included each participant's address and the names of family members. In order for the researchers to be sure they did not lose track of their subjects, all were asked to name close friends who would know where they were at the time of their next exam, in roughly four years. Since much of the town and most of the subjects' relatives were participating, the data contained all that Christakis and his colleagues needed to reconstruct the social network and follow it for 32 years.

    Their research has taken obesity specialists and social scientists aback. But many say the finding is path-breaking and can shed new light on how and why people have gotten so fat so fast.

    "It is an extraordinarily subtle and sophisticated way of getting a handle on aspects of the environment that are not normally considered," said Dr. Rudolph Leibel, an obesity researcher at Columbia University in New York.

    Dr. Richard Suzman, who directs the office of behavioral and social research programs at the U.S. National Institute on Aging, called it "one of the most exciting studies to come out of medical sociology in decades." The National Institute on Aging funded the study.

    But Dr. Stephen O'Rahilly, an obesity researcher at the University of Cambridge in England, says the very uniqueness of the Framingham data is going to make it hard to try to replicate the new findings. No other study he knows of has the same sort of long term and detailed data on social interactions.

    "When you come upon things that inherently look a bit implausible, you raise the bar for standards of proof," O'Rahilly said. "Good science is all about replication, but it is hard to see how science will ever replicate this."

    Watch the video: Entertv: Άκης Πετρετζίκης: Αποκαλύπτει γιατί σταμάτησε πρόωρα η βραδινή του εκπομπή (June 2022).


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