Whole Health Source: Is the "Obesity Paradox" an Illusion?
Stephan Guyenet has just wrote a post that makes some good arguments against the Obesity Paradox. He argues that the Obesity Paradox is the result of poor observational research methods that fails to account for disease causing people to go from overweight -> thin and fails to fully adjust for unhealthy habits, like smoking, that make people thin.
He supports this with evidence from new research methods used that account for body weight history, and not body weight at time of diagnosis.
Stephan Guyenet has just wrote a post that makes some good arguments against the Obesity Paradox. He argues that the Obesity Paradox is the result of poor observational research methods that fails to account for disease causing people to go from overweight -> thin and fails to fully adjust for unhealthy habits, like smoking, that make people thin.
The fundamental problem with the obesity paradox is that it's based almost entirely on observational evidence, meaning that it doesn't come from controlled experiments that are better at identifying cause-effect relationships. And in this particular case, it's not hard to imagine ways in which observational methods could obscure the true relationship between body fatness and health. In other words, the obesity paradox could be nothing more than an illusion of the particular research methods that were used to identify it**.
How might this work? As an example, we know that illnesses such as diabetes and Alzheimer's disease often lead to weight loss (sometimes many years before diagnosis, meaning that you can't entirely eliminate the problem by excluding people with diagnosed disease). So if you're currently lean and sick, researchers may associate your illness with the lean category, even if you used to be overweight, and even if that excess fat caused your illness to begin with.
A similar phenomenon happens with cigarette smoking. Smoking causes weight loss, and it's also a fast track to illness and premature death. It's not hard to imagine how smokers might make leanness look a lot more dangerous than it really is. It's also not hard to imagine that some smokers don't accurately report their smoking habits, making it difficult to fully account for in studies.
He supports this with evidence from new research methods used that account for body weight history, and not body weight at time of diagnosis.
Yet a new research method developed by Andrew Stokes, assistant professor of global health at Boston University, promises to provide the clearest picture yet of the true relationship between body weight and health.
To minimize the pitfalls of traditional methods, Stokes looks not only at current body weight, but atweight history. He asks a simple question: how does a person's maximum attained weight associate with health outcomes? Weight is compared using the body mass index (BMI) scale, which corrects for the effects of height on weight.
Maximum weight should do a better job of capturing the effect of excess body fat on health, because traditional methods don't consider the possibility that a person might have previously carried more fat, and may have been exposed to its damaging (or protective) effects for many years. If this is true-- which seems fairly obvious to me-- then Stokes's method is a better test of the obesity paradox hypothesis than previous methods.
In 2014, I wrote about Stokes's first study using this method, which suggests that lean people have lower mortality levels than people who are overweight or obese (8). Recently, Stokes and his mentor Samuel Preston published two more papers on the subject, and they are much more detailed (9).
Using the maximum weight method, Stokes confirmed his previous finding that people who remain lean throughout life have the lowest risk of dying. Consistent with this, they also have the lowest risk of developing diabetes and cardiovascular disease. Both associations were substantial. Furthermore, people who already have diagnosed cardiovascular disease have a higher risk of dying if they're also obese, not lower. There is no paradox in these data, which is a good sign that we finally understand what's going on. It's also reassuring that his results align well with what we know from experimental studies in animals and humans.