Nanci Hellmich, USA TODAY
Understanding the 'obesity paradox': People who are overweight may have a lower risk of early death than those at a normal weight.
Folks who are just slightly overweight but have resolved to lose weight in the new year may give their plans second thoughts in the wake of a controversial new federal analysis.
People who are overweight by up to 30 or so pounds have a slightly lower risk of early death than those at a normal weight, the government analysis finds.
The review of 97 studies showed that people who are extremely obese -- roughly 60 or more pounds over a normal weight -- have a greater risk of dying early than those who are at a normal weight.
About two-thirds of people in the USA are too heavy; a third are obese, which is roughly 35 or more pounds over a normal weight. Obesity is linked to an increased risk of type 2 diabetes, heart disease, stroke and many types of cancer.
Katherine Flegal and colleagues at the National Center for Health Statistics, part of the Centers for Disease Control and Prevention, reviewed the studies, which tracked 3 million adults from around the world. The research looked at deaths from all reasons and people's body mass index (BMI), a number that considers weight and height.
The standard BMI categories included: normal weight (a BMI of 18.5 to 24.9); overweight (BMI of 25 to 30); obese (a BMI of 30 or more); extremely obese (a BMI of 35 or more).
Findings, published in Wednesday's Journal of the American Medical Association, show that relative to normal-weight people those who were:
- Extremely obese had a 29% increased risk of early death.
- Obese had an 18% increased risk of early death.
- Overweight had a 6% lower risk of early death.
"People are sometimes amazed that overweight people have a lower mortality than normal-weight people, but a lot of the research has shown this for a long time," says Flegal, the lead researcher on the study.
Walter Willett, head of the department of nutrition at the Harvard School of Public Health, says the findings are "complete rubbish" because the methodology used in the analysis seriously underestimates "the hazards of being overweight and obese."
"There have been two major reports published in the last several years that used the original data from over 60 studies to look at the risk of being overweight and obese," he says. "These both showed clear increases in mortality in overweight and slightly obese people. This is also supported by dozens of studies showing increased risks of type 2 diabetes, cardiovascular disease, many types of cancer and many other conditions among those who are overweight and obese."
"Thus, a vast amount of data show clearly that there are many adverse consequences of overweight and obesity, including greater hazards of premature death," Willett says.
People shouldn't interpret the government analysis to think that it is now OK to be overweight, says Steven Heymsfield, one of the authors on the accompanying editorial in the journal and the executive director of the Pennington Biomedical Research Center in Baton Rouge. "We don't really know the ideal weight for a long life and optimal health. Science is still working that out. But falling in the normal, healthy weight range is still the safest place to be."
Gordon Tomaselli, immediate past president of the American Heart Association and director of the division of cardiology at the Johns Hopkins University School of Medicine in Baltimore, says, "We advocate for people maintaining an ideal body weight. Other studies consistently show that being excessively overweight increases mortality."
Flegal says there are numerous possible suggestions that experts have given for the lower risk of early death among those who are overweight. "There's something called the obesity paradox. If for example, people end up having a surgery or (being treated) in the ICU, the heavier people may survive better. We don't know why, but there's a lot of research that suggests this."
Some people have suggested that "if you are sick, there is a lot of extra demands and stress on your body with tests and treatments, and maybe if you have a little extra weight, you are better able to deal with these," she says.
Others have suggested that if you are heavier you may get screened more often by the doctor, and you may get diagnosed earlier for different conditions, Flegal says. And there are some suggestions that doctors are more likely to follow the right clinical guidelines in the treatment of heavier people than normal-weight people. So it's possible that normal-weight people are sometimes getting less than optimal treatment, she says.
Some have suggested that there may be some benefits to fat tissue, Flegal says.
"These are just suggestions. No one knows the answer."
Heymsfield's advice to those resolving to lose weight in the new year: "The evidence is pretty strong that if you are obese, there is no question you should try and get your weight down.
"But if you are overweight, you need to make sure you are healthy on all fronts -- blood pressure, cholesterol and type 2 diabetes. Minimally, you want to prevent further weight gain, and ideally you want to get down to the normal range, if you can, particularly if you have a health risk factor," he says.