Obesity is Harmful, and Studies that Suggest Otherwise Made Overly Simplistic Use of Data

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."

Link: http://www.upenn.edu/pennnews/news/obesity-does-not-protect-patients-with-cardiovascular-disease

Comments

Obesity is bad. In other news: water is wet.

I'm kind of amazed anyone would really try argue otherwise.

Posted by: Ham at October 13th, 2015 12:02 PM

The problem, Reason, is that it isn't so easy to tell which side is doing the cherry-picking. There isn't a mountain of evidence linking fat to shorter life expectancy. "study after study" shows overweight and obese people having similar or lower mortality than people in the normal range, and definitely lower than underweight. There are plenty of studies that have focused on only never smokers that still find overweightedness being not a big deal in terms of mortality. Weight history might be the missing link, true, but like you said, you shouldn't focus too much on one study. Also, note, this paper is about mortality once you already have CVD, a small part of the whole puzzle.

If you want particular criticism of this study: it's a retrospective study where they are printing the final set of variables that gave a p < 0.05 but didn't list all the ones they looked at, and as usual, they most likely did no correction for this on their p-levels. To their credit, the ones they ended up with seem quite "natural" which means there might not be too much cherry-picking going on, but given their p is at 0.021, even a small correction (eg even if they would have looked at two other variations) would have blown their "statistical significance". Their sample set is pretty small (300 people in the normal set overall, don't even show how many were never-smokers, never-overweight). They grouped overweight/obese together (for statistical power is the most charitable interpretation). Weight history was partially self-reported. Likely confounders: never-smoked, never-overweight people likely to be more conscientious => lower mortality.

Note also which way the natural bias would go. Fat people are low status and there is a natural bias towards trying to make it appear bad for a long time (eg gluttony being a deadly sin). If you think overweight people are being told that everything is fine, you definitely live in a different society to the one I live in.

Full disclaimer: I'm one of those never-smoked, never-overweight people that think we are wasting a whole bunch of money, mental energy, and words trying to find ways to make fat people look bad. I do also suspect that carrying fat around is bad for mortality, especially when young, but that the effect is very small compared to the coverage and focus that is given to it.

Posted by: ale at October 13th, 2015 8:32 PM

Ale, I disagree with your comments that "we are wasting a whole bunch of money, mental energy, and words trying to find ways to make fat people look bad".

The body works much better when it is not overweight. Avoiding being overweight by exercising and eating healthy (mostly) can help reduce high blood pressure, and avoid diabetes, heart problems, some cancers, and have more energy.

People who refuse to exercise (I hate going to the gym but managed for 15 years) and end up getting heavier (most people gain weight in their 40's and 50's) as their metabolism slows down.

Besides getting heavier which ends up causing health problems, it is adding to the health costs around the country.

Smoking and getting overweight are my two pet peeves. My dad died from emphysema several years ago and my mom who has been overweight for most of her life is now on dialysis and is diabetic.

Posted by: Robert Church at October 13th, 2015 10:41 PM

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