Being fat isn’t always a bad thing, according to two studies by European and U.S. researchers.
Obese people who are otherwise physically fit had no greater risk of dying prematurely than those whose weight is normal, according to research partially funded by the U.S. National Institutes of Health and Coca-Cola Co., the world’s biggest soft-drink maker. A separate study found that obese people with heart disease have a lower risk of dying early than underweight or normal-weight heart patients.
The findings undermine decades of public health messages, also supported by research, that obesity can accelerate the development of heart disease, diabetes and cancer and shrink lifespans, three European researchers who weren’t involved in the two studies wrote in an editorial that accompanied the results in the European Heart Journal today.
“The prevailing wisdom holds that being slim must be generally good for you,” Stephan von Haehling, Oliver Hartmann and Stefan Anker wrote in the editorial. “Obesity may carry a benefit up to a certain degree, and it should be recognized that obesity is not necessarily associated with abnormal metabolic function.”
The findings don’t give people license to expand their waistlines, said Amy Thompson, a senior cardiac nurse at the British Heart Foundation. Instead, the studies serve as reminders that carrying fat around the belly and how fat affects your fitness may be more important than the numbers on the scale, Thompson said.
“In the majority of cases, obesity is an undeniable risk factor for developing coronary heart disease,” Thompson said in a statement. “However, these studies remind us that it is not always your weight that’s important, but where you carry fat and also how it affects your health and fitness.”
Obesity belongs to a group of early warning signs of heart disease and diabetes known as metabolic syndrome, which affects about 25 percent of the world’s adults, according to the Brussels-based International Diabetes Federation. Obesity is usually defined by body mass index, which is calculated using a person’s height and weight. The researchers in the first study used body fat measurements taken from skin folds or using water displacement, techniques thought to be more accurate than BMI.
“Previous studies have said if you’re obese, you’re always in a higher risk group,” Francisco Ortega, the lead author of that study, said in a telephone interview. “What they didn’t look at was fitness. This brings fitness into the picture.”
Ortega’s study involved more than 40,000 U.S. adults recruited for the Aerobics Center Longitudinal Study. The participants -- who were mostly Caucasian, male and well educated -- each completed a questionnaire about lifestyle and medical history, and underwent a physical exam, blood tests and a treadmill test between 1979 and 2003.
In addition to the NIH and Coca-Cola grants, the research was funded by the Spanish Ministry of Science and Innovation and the Swedish Heart-Lung Foundation. Coca-Cola’s funding supported one of the co-authors, and the company had no role in or influence over the research, Ortega said.
For their study, Ortega and his colleagues considered the obese participants “metabolically healthy“ if they had only one of the following conditions: high blood pressure, low levels of so-called good cholesterol, high triglyceride levels and high fasting glucose level. About 46 percent of the obese people in the analysis met that definition.
Obese people who were metabolically healthy had a 38 percent lower risk of early death from any cause, compared with obese people who had two or more indicators of disease, according to the study. The obese yet healthy people also had a reduced chance of developing cardiovascular disease and cancer, the researchers found.
The results aren’t a complete surprise, because in real life, not all obese people have the same prognosis, William Zoghbi, president of the American College of Cardiology, said in a telephone interview.
“This provides evidence that this is the case,” said Zoghbi. “Obesity is still a risk, but with gradation. Personally, I’d encourage fitness in all individuals, but it’s more important in a person who’s overweight or obese.”
Doctors, in addition to standard blood tests, should consider using body fat measurements and some assessment of physical fitness when deciding whether obese patients are at risk of developing chronic illnesses and need treatment, Ortega said.
“Very few physicians take into account these measurements,” he said.
People shouldn’t use the findings to become complacent about their fitness, Ortega said.
“I wouldn’t tell everyone that it’s all fine,” he said. “If you’re normal weight or overweight, you should still exercise. If you don’t reduce your weight with exercise, but are fit, you’re at a much lower risk than if you’re unfit.”
In the second study, researchers led by Swedish cardiologist Oskar Angeras analyzed data from more than 64,000 patients who had developed acute coronary syndromes such as heart attacks. The authors declared no funding sources or conflicts of interest.
Patients who were underweight, with a BMI of less than 18.5, had the greatest risk of dying prematurely, they found. Those with the lowest risk of early death had a BMI between 26.5 and 35. The study lacked sufficient data on patients with a BMI of more than 35, the editorialists wrote.
While being overweight or obese can hasten the beginning of heart disease, once the illness has developed, carrying extra fat doesn’t affect the risk of a premature death, the researchers said. The findings of the observational study support previous evidence of this so-called obesity paradox, which should be examined further, they said.
“No evidence exists that proves weight reduction in itself has a positive prognostic value after acute coronary syndromes,” the researchers wrote in the study, which was also published in the European Heart Journal. “Actually, some evidence suggests that weight loss after acute coronary syndromes might in fact have a negative effect.”
The paradox may be explained by body fat’s action as an endocrine organ, or as protection against hip fractures, von Haehling, Hartmann and Anker wrote in the editorial.
“The available studies, together with previously published data, permit the conclusion that weight loss in patients with chronic illness and a BMI of less than 40 is always bad,” they said.