A startling new study by medical researchers in the United States has caused consternation among public health professionals by suggesting that, contrary to conventional wisdom, being overweight might actually be beneficial for health.
The study, published yesterday in the respected Journal of the American Medical Association, runs counter to almost all other advice to consumers by saying that carrying a little extra flab – though not too much – might help people to live longer.
Struggling dieters, used to being told that staying thin is the best prescription for longevity, are likely to be confused this morning if not heartily relieved. While being a bit overweight may indeed increase your chances of dying from diabetes and kidney disease – conditions that are often linked with one another – the same is not true for a host of other ailments including cancer and heart disease, the report suggests.
In fact, scanning the whole gamut of diseases that could curtail your life, being over weight is, on balance, a good thing. The bottom line, the scientists say, is that modestly overweight people demonstrate a lower death rate than their peers who are underweight, obese or – most surprisingly – normal weight.
The findings will be hard to dismiss. They are the result of analysis of decades of data by federal researchers at the Centres for Disease Control and Prevention (CDC) in Atlanta, Georgia. This is not a study from a fringe group of scientists or sponsored by a fast-food chain.
Being overweight, the report asserts in its conclusions, "was associated with significantly decreased all-cause mortality overall".
"The take-home message is that the relationship between fat and mortality is more complicated than we tend to think," said Katherine Flegal, the lead researcher. "It's not a cookie-cutter, one-size-fits-all situation where excess weight just increases your mortality risk for any and all causes of death."
That the CDC has even published the report and thus threatened to muffle years of propaganda as to the health benefits of staying slender has enraged some medical experts.
"It's just rubbish," fumed Walter Willett, the professor of epidemiology and nutrition at the Harvard School of Public Health. "It's just ludicrous to say there is no increased risk of mortality from being overweight."
Not that the CDC results are an invitation to throw caution to the winds and take cream with everything. The scientists are careful to stress that the benefits they are describing are limited to those people who are merely overweight – which generally means being no more than 30 pounds heavier than is recommended for your height – and certainly do not carry over to those who fall into the category of obese.
Obesity has been declared one of the main threats to health in the US, including among children. Those considered obese, with a body mass index (BMI) of more than 30, continue to run a higher risk of death, the study says, from a variety of ailments, including numerous cancers and heart disease. It said that being underweight increases the risk of ailments not including heart disease or cancer.
The scientists at the CDC first hinted at the upside of being overweight a few years ago. Since then, however, they have expanded the base of their analysis, with data that includes mortality figures from 2004, the last year for which numbers were available, for no fewer than 2.3 million American adults.
Highlighting how a bit of bulge might help you, the scientists said that in 2004 there were 100,000 fewer deaths among the overweight in the US than would have been expected if they were all considered to be of normal weight. Put slightly differently, those Americans who were merely overweight were up to about 40 per cent less likely than normal-weight people to die from a whole range of diseases and risks including emphysema, pneumonia, Alzheimer's, injuries and various infections.
Aside from escaping diseases, tipping the scales a little further may also help people recover from serious surgery, injuries and infections, Dr Flegal suggested. Such patients may simply have deeper bodily reserves to draw on in times of medical crisis.
Not everyone in the medical profession was surprised or angry about the study. "What this tells us is the hazards have been very much exaggerated," said Steven Blair, a professor of exercise science and biostatistics at the University of South Carolina, who has long argued that the case for dietary restraint has been taken too far.
"I believe the data," added Elizabeth Barrett-Connor, a professor of family and preventive medicine at the University of California, San Diego, who believes that a BMI of 25 to 30 – roughly the the so-called overweight range – "may be optimal".
Critics, however, were quick to point out that the study was concerned with mortality data only and did not take account of the quality of life benefits of keeping your weight down. The study "is not about health and sickness", noted the obesity researcher Barry Popkin of the University of North Carolina.
The report "definitely won't be the last word", said Dr Michael Thun of the American Cancer Society, who pointed out, in a report released last week by the World Cancer Research Fund and the American Institute for Cancer Research, that staying slim was the main recommendation for avoiding cancer.
Others in the American medical community, while a little bemused, were withholding judgement. "This is a very puzzling disconnect," said Dr JoAnn Manson, the chief of preventive medicine at Harvard's Brigham and Women's Hospital.
The suggestion that a bit of extra weight may assist patients recovering from an infection or surgery was of no surprise to Dr Flegal. "You may also have more lean mass – more bone and muscle," she said. "If you are in an adverse situation, that could be good for you."
In their conclusions, the authors of the study note: "Overweight... may be associated with improved survival during recovery from adverse conditions, such as infections or medical procedures, and with improved prognosis for some diseases. Such findings may be due to greater nutritional reserves or higher lean body mass associated with overweight."
Those of us mostly likely to benefit from a little bulge beneath the belt, the study adds, are between 25 and 59 years old, although there were also some advantages for people over 60.