How Fat is Fat?

A recent meta-analysis of a large number of studies on the effect of body mass has revealed a result counter to common wisdom, being overweight, including being slight obese actually seems to reduce the morbidity compared to people of "normal" and less weight.

Rather than Nanny Bloomburg going out and passing a New York City regulation requiring everyone to have at least one 32 oz fructose bearing carbonated drink in an effort to bring everyone up into the weight zone of minimal morbidity, or my own reaction, to reach for another doughnut, this has left epidemiologists struggling to maintain the narrative that thin is healthy as well as beautiful.

William Saleten of Slate has collected a large number of "but" arguments to this finding, and considers them, in what I think is a pretty fair and insightful analysis:

Epidemiologists struggle to explain a study that challenges a core belief: Fat will kill you.

1. The difference is barely significant. In the JAMA analysis, overweight people were just 6 percent less likely to die than normal-weight people. “It's probably only statistically significant because of the large number” of people in the combined data set, says one skeptic. Maybe. But if the correlation had gone in the other direction—showing a marginally higher death rate among the overweight—you wouldn’t hear scientists arguing that what’s statistically significant isn’t really significant.

Exactly right; if the results of the meta-analysis had confirmed their preconceptions the large sample size necessary to find statistical significance would not have been an issue to them.  A similar meta-analysis was used to find the relationship between second hand smoke and sickness which has been used as the excuse reason to regulate smoking in public places.  However, the fact that a meta analysis was require suggests the results of the individual studies was mixed, and evidence for causality weak.

2. Death risk is the wrong standard. So what if fat doesn’t correlate with mortality? It still correlates with many diseases, which may ultimately affect mortality.

Perhaps, but it's an important standard.  If it's causing a lot of other diseases, apparently they're not killing us.

3. Overweight is too close to obese. We used to think that being overweight gave you a higher risk of death. Then we collected data that suggested overweight might be OK but obesity was still deadly. Now we have data that suggest even mild obesity may be OK. To account for this, weight-control advocates are adding another link to their long-standing sermon: If you’re overweight, you’re on the road not just to mild obesity but eventually to morbid obesity, which the JAMA analysis validates as a huge mortality risk (with a 29 percent higher likelihood of death).

Undoubtedly true for some, but not for all,  many people struggle somewhat with obesity their whole life without succumbing to morbid obesity.  And these people seem to stand to benefit from it!  Drat!

4. The dangers of being underweight hide the dangers of being overweight. A JAMA editorial notes that people in the thinner half of the “normal” BMI range have a higher mortality rate than those in the plumper half. This thinner subset inflates the normal-weight group’s mortality rate, which makes the mortality rate among overweight and obese people look good by comparison. The solution is to shift the whole scale to the right, so that these thin people are recognized as underweight, while people presently labeled overweight are redefined as normal weight...

An interesting data point, noting that the thin side of "normal" also has a downside.  Have another donut.  It seems that society is adopting this view unconsciously.  Many have noted that heavy is the new normal, and except for movie stars; most of us are OK with it.

5. Some kinds of fat are worse than others. At the moment, scientists seem to agree that while belly fat is bad for you, butt and thigh fat might be safe or even beneficial. So instead of focusing on BMI, we should measure your waist-to-hip ratio, body-fat percentage, blood pressure, blood lipids, glucose, and cardio-respiratory fitness.

Shoulda, woulda, coulda.  But the studies weren't done that way apparently, or at least not consistently enough to use the data.  It's probably true, but then people who get fat in the hips and thighs would have to authorized to drink 32 oz high fructose soft drinks, while those of us who accumulate belly fat would be denied them.

6. Fat helps you survive some diseases. The JAMA editorial points out that among people suffering “a wasting disease, heart disease, diabetes, renal dialysis, or older age,” higher BMI correlates with a lower mortality rate. “Even in the absence of chronic disease, small excess amounts of adipose tissue may provide needed energy reserves during acute catabolic illnesses.” That doesn’t mean fat makes you healthy. It means that once you’re unhealthy, fat might keep you alive, at least for a while.

You mean, the body uses fat to survive the lean, bad times?  Whoda thunk?

7. Fat protects you against injury. Many old people die from falls. Chubbier people “have more padding to protect the bones should a patient take a tumble, lowering the risk of a life-endangering hip fracture,” notes the Los Angeles Times.

Time for another doughnut already; they're actually starting to make fat sound good. 

8. Muscular people inflate the survival rate of the fat group. BMI “doesn't differentiate between fat and muscle mass,” observes the Wall Street Journal. So people who exercise and gain muscle are counted as fatter, when really they’re just stronger.

Now there's my problem; too much muscle being measured as fat.   

9. Sick people depress the survival rate of the “normal” group. The JAMA analysis controlled for smoking and pre-existing disease, and it didn’t include anyone in a hospital or hospice. But critics aren’t mollified. They insist, according to the Associated Press, that the normal-weight sample unduly “included people too thin to fit what some consider to be normal weight, which could have taken in people emaciated by cancer or other diseases.” It would take further, more precise studies to falsify this assertion.

Are they arguing that the "normal" group contains people who are really fat people who are skinnier than they "should be" because they're ill?  But there are no fat people who would be skinny people because they are ill?  This is getting to be pretty convoluted reasoning.

10. Overweight gets you more medical attention and intervention. Doctors’ belief that fat signals a health risk makes them more likely to scrutinize heavier patients for disease symptoms or risk factors. Lots of evidence suggests doctors treat these patients more aggressively, thereby reducing mortality. In this way, the medical profession’s assumption that weight correlates with illness makes that correlation less visible in mortality data.

Doctors are prejudiced in favor of against fat people? And that get's them more treatment?  And if doctors started treating mild obesity as normal, they would start to die at a rate that would satisfy the critics?  So we need rules to cut down the attention that fat people get from doctors?  Weird. 

11. Medicine has made fat less harmful. “New pharmacological therapies and invasive treatments for existing disease may prolong survival,” the JAMA editorial points out. These and other advances, particularly those that reduce cholesterol and blood pressure, “may account for the weakening of associations between obesity and mortality.”

Another weird argument.  If true it would suggest that medicine has been better for fat people than for "normal" and "thin" people.  Do we have to demand that modern medicine be withdrawn from fat people so that we can get them us back to the politically correct higher level of morbidity?  Besides, they never really established the association between obesity and mortality to begin with, which is why this study was of interest to begin with.

12. Overweight doesn’t mean you’re getting fat. It means you’re resisting obesity. "In a society prone to both epidemic and increasingly severe obesity, it may be that those who manage to remain in the 'overweight' class are, in fact, those who are actually doing quite well," says David Katz, director of Yale’s Prevention Research Center. So instead of seeing these people as formerly thin folks with bad habits, we should see them as fat-prone folks with good habits. How this squares with the notion of overweight as a gateway to obesity—a warning echoed by Katz—isn’t clear.

It's all pretty strange stuff.  They are trying desperately to find arguments to maintain their war on overweight and mild obesity (there's really no question that extreme obesity is a problem).

On one level, these explanations sound weak and weaselly. Dogmas, even in science, don’t surrender easily to contrary evidence. Experts who think weight gain is dangerous will find ways to reaffirm that belief, explaining away data that don’t fit it. But science, in its grudging way, does evolve. The explanations offered today in defense of the fat-is-bad doctrine are actually modifications of it. They’re taking us beyond crude categories such as BMI, overweight, and fat. A decade from now, we’ll still believe fat is bad for you, but we’ll be far more sophisticated in what we mean by “bad” and “fat.” And the JAMA study’s critics, like its defenders, will take the credit.

And I predict, confidently, that people will still be fat a decade from now, and they'll still be looking for reasons for people to lose weight.