Researchers here reinforce the point that, yes, being obese is bad for your health, and that a few prior studies that suggested otherwise were mistaken. In any field there are always going to be studies that appear to go against the grain to provide contradictory results. Most of the time these are errors of interpretation; scientific research is hard and complicated, and as a consequence a lot of published work is incorrect in some way. That is why one should never take any single paper in isolation, but look at it in the context of the broader field. In the case of excess fat the broader field has provided a mountain of evidence to show that adding and maintaining more fat tissue causes worse health, greater medical expenditures, and a shorter life expectancy.
It is unfortunate that some factions within our society are willing to cherry pick research to support and propagate the mistaken belief that being overweight is safe and has no effect on health. Everyone who has managed to get themselves into a deep hole wants to be told that they are just fine and haven't caused any harm, but that doesn't make it true.
Researchers set out to solve a puzzle: Why is it that study after study shows obese or overweight people with cardiovascular disease outliving their normal weight counterparts? Would this phenomenon, referred to as the obesity paradox, hold up when approached within different parameters? According to their latest research, the answer is no. When accounting for weight history in addition to weight at the time of survey and when adding in smoking as a factor, obesity is harmful, not helpful, to someone with cardiovascular disease. "There are claims that ... it's good to be obese when you have cardiovascular disease, that if you have fat stores, maybe you'll live longer. It's conceivable that there are health advantages. But we show they are overwhelmed by the disadvantages of being obese, once you control for these two sources of bias."
The researchers started with data from more than 30,400 participants of the National Health and Nutrition Examination Survey between 1988 and 2011. The survey is a nationally representative sample considered the gold standard in the United States. Of those participants, 3,388 had cardiovascular disease. Most research of this type looks only at weight at time of survey. For example, if a participant who long weighed 300 pounds lost one-third of his mass by the time he weighed in, he would be counted at 200 pounds. Not including weight history, however, "would be like classifying a lifelong smoker who quit the day before the survey as a non-smoker, even though we know that if you're a lifelong smoker you carry those risks over even if you stop smoking."
Adding weight history "turns out to have a profound effect on the findings," eliminating the mortality advantage for those who are overweight or obese. Incorporating the second factor, smoking, also contributed to resolving the paradox. Smokers are less likely to be obese, and those who are obese are less likely to smoke. This correlation is much stronger for those with cardiovascular disease, so the researchers limited their pool to lifelong non-smokers. Accounting for weight history makes the obesity paradox disappear. Excluding smokers? That's when being obese equates to significantly higher mortality for those with cardiovascular disease.
The researchers said these results could improve disease treatment, since some clinicians may use the obesity paradox in patient care decisions. "There's every reason to imagine that clinicians are at least confused, and in some cases, are believing that being overweight or obese is a good thing among people with cardiovascular disease, diabetes and other conditions for which a paradox has been demonstrated." Conditions like stroke, kidney disease and high blood pressure, for example. "This may be trickling down into clinical decision making, which is concerning because we don't think it's a real finding."