No obesity paradox

Published 11.17.2016
Cleaning out the draft bin a bit today. More evidence that there is no obesity paradox. The actual study, which was published back in July, can be read here. The first two quotes below are from the Med Page Today link.

A massive meta-analysis pooling data from millions of people in several countries reaffirmed that body mass index (BMI) has a J-shaped relationship with mortality, with the lowest death rates among those in the traditional "normal" range of 20-25.

The study of nearly four million people revealed that those in every BMI category above and below the normal range had significantly higher mortality rates.

The effects were worse for younger people. Smokers were excluded from the analysis.

This analysis pooled 239 studies across 32 countries and included about 1.6 million deaths. Only data from large, prospective studies was included, and only studies performed after 1970 were included. The hazard ratios of all-cause mortality were generally similar across different continents, though the risk was higher for underweight and for the highest class of obesity in Europe than in East Asia.

Yes, the analysis was based on BMI (body mass index), which can be an inaccurate marker of obesity— mostly in people with high lean body mass (muscles) for their height. Generally, for people with 40% body fat and greater, BMI does just fine. That's not a point often admitted amongst those slamming BMI as a marker, but it is the truth. Plus, as this is a study making population comparisons, BMI actually is the appropriate, if imperfect, variable to compare.

Please note that the fact that there is no obesity paradox in no way means that fat-shaming or body shaming is acceptable or that fat people are in any way less deserving of respect in our society. There is no requirement to be any particular size, but there is, at least in my world, a need to recognize the facts, even unpleasant ones.

The unpleasant fact is that adipose tissue, like every other part of the body, plays a role in the body's health and function.
Here is Carson Chow's take on the study. Chow says he used to like to shock people by saying that being fat wasn't so bad. Unfortunately, the Lancet study disproves that sentiment.

The study also found higher risk of mortality for people who are underweight, defined as a BMI of less than 20. In fact, the hazard ratios for underweight were worse than those for type one obesity, defined as BMI 30-35. Overweight (BMI 25-30) had very similar hazard ratios to "normal" weight (BMI 20-25). These results illustrate why it's important to differentiate between overweight and obese. Too often they are conflated.

Overweight status is easier, I think, for many to achieve, and perhaps suggests why a relatively small amount of weight lost can have such a huge, positive, effect on health. Losing 10% of body weight if a man has a BMI of 34 puts him at a BMI of 30, which is top end of overweight. My observation is the body can compensate for a decent amount of excess adipose. In fact, excess fat stores are a reserve to draw on in times of bodily crisis (illness, starvation etc). However, and I've said this previously, once the amount of excess adipose (fat) becomes more than the body can handle, the wheels start to come off.

How might the wheels come off? The fatter you are, the higher the inflammation in your body, and the more likely you are to be demented.

Using two separate samples from the study — one of about 9,000 people and one of about 12,500 — researchers looked at aging adults over a six-year period. They had information on study participants' BMI, inflammation and cognition, and they found the same outcome in both samples.

"The higher participants' body mass at the first time point in the study," Bourassa said, "the greater the change in their CRP levels over the next four years. CRP stands for C-reactive protein, which is a marker in the blood of systemic inflammation in your body. Change in CRP over four years then predicted change in cognition six years after the start of the study. The body mass of these people predicted their cognitive decline through their levels of systemic inflammation.

Risks of other conditions increase too: type two diabetes, cardiovascular disease, high blood pressure, etc. (Remember: I am not any kind of medical professional.) If you're happy being obese, then I'm happy for you. But there are consequences for remaining that size.


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