The Truth Behind the Obesity Paradox

In my opinion, the short answer to the obesity paradox is that it doesn’t really exist. But what fun would that be? That doesn’t teach you anything. Let’s take a look at the problems with the research that contributed to this paradox.
 

Study One: Dialysis, BMI, and Mortality

A study of dialysis patients led to the first observation that people with higher BMIs lived longer (1). After tracking over 1,300 subjects on dialysis for a year, researchers found that those who were overweight had a decreased risk of dying and had fewer hospital stays when compared to those who were underweight. This may have been the study that yielded the name The Obesity Paradox. The problem? The study lasted only one year. Trying to generalize what will happen to all overweight and obese people on dialysis from a study that lasted only one year and at only a single location isn’t realistic. It raises an intriguing question, but we’ll need a much more extensive study to really make a solid prediction.
 

Study Two: The Rotterdam Study

I described this study on Thursday (2). While the study appeared to show a protective benefit from being overweight or obese, the subjects were elderly with an average age of 77 at the study’s beginning. One risk factor that you cannot change is age: the older you are, the more likely you are to die. But that’s not the whole story. We can probably say that older people may live longer with a little extra weight, but to extend that prediction to all age groups isn’t valid.
 

Study Three: BMI and Mortality

While this study claimed to analyze the data on over two million people, it was still a meta-analysis (3), which doesn’t yield cause and effect, just a statistical association. Further, they used studies of varying lengths without necessarily knowing exact causes of deaths. They also did not have precise BMIs on everyone; some studies included metrics such as BMI under 27.5 and over 27.5. They tried to include the highest number of subjects, but the quality of data varied and that made it a mess. Researchers chose too many different types of studies in the meta-analysis, and it just doesn’t work. I wouldn’t bet my life on it.
 

Study Four: A Broader Look

The real problem with every approach is the lack of acknowledgement that people with advanced disease may have lost weight before they were included in the study; diseases such as heart failure, diabetes, or renal disease will often lead to weight loss. Those who were heavier when disease hit had the benefit of extra energy stored as fat to deal with the disease, and that could explain the outcomes of those studies. It had nothing to do with being obese; it was a matter of timing.

A study published last month appears to confirm that (4). Researchers in the Cardiovascular Disease Lifetime Risk Pooling Project obtained data from 10 different longitudinal studies, including individual-level data and accurate mortality data. They found that as BMI increased, the death rate from all forms of CVD increased. For those who carried extra weight while younger, CVD occurred earlier, making it more likely they would die before their time.
 

The Bottom Line

As I said, there really is no obesity paradox. Being overweight or obese carries with it risks of degenerative disease. Some people may have better genes and may gain protection for a few years. But in the end, being overweight or obese carries a higher risk of various diseases than the limited protection from an advanced disease you may gain by carrying extra weight. So my advice is the same as it always was: if you’re overweight, your best bet for a long, healthy life is to lose it.

What are you prepared to do today?

Dr. Chet

 

References:
1. Kidney International, Vol. 55 (1999), pp. 1560–1567.
2. European Heart Journal (2001) 22, 1318–1327.
3. JAMA. 2013; 309(1): 71–82.
4. JAMA Cardiol. doi:10.1001/jamacardio.2018.0022.