Sunday, June 23, 2013

Obesity is now a Disease

There’s been a lot of talk about the American Medical Association having recently classified obesity as a disease. 

Is Obesity a Disease? 

I Googled some definitions.  From biology online: 

An abnormal condition of an organism which interrupts the normal bodily functions that often leads to feeling of pain and weakness, and usually associated with symptoms and signs. 

A pathologic condition in which the normal functioning of an organism or body is impaired or disrupted resulting in extreme pain, dysfunction, distress, or death. 

And from Wikipedia: 

The term disease broadly refers to any condition that impairs normal function, and is therefore associated with dysfunction of normal homeostasis. 

There appears to be two main points among these definitions: 

  • Diseases impair/interrupt normal (physiological) function
  • Diseases have signs and symptoms 

Obesity, which is defined as a BMI ≥ 30, can impair normal physiological function most notably in insulin resistant obesity where large adipocyte cell size leads to elevated free fatty acids and hypoxia, which in turn causes inflammation, insulin resistance and fat deposition in the liver*.  Although if adipocyte cell size remains normal (insulin sensitive obesity) there might not be much impaired function, besides athleticism. 

As for signs and symptoms this is where it gets telling.  A sign of obesity could be large waist circumference, but that’s really defining obesity in a more valid way than BMI (which by the way is good enough in most, but not all contexts) and is a more reliable predictor of insulin resistant obesity.  Obesity is the symptom 

About a year ago I wrote a post titled ‘Obesity: a Symptom of an Underlying pathology’ (so you can already see where I stand).  When I changed the format of the blog I broke it into 5 different posts, but the most important one is Leptin Resistance, where provide I evidence for the following:

Mitochondrial dysfunction >> ER stress >> PTP1B >> leptin resistance >> obesity
LPS and other factors >> inflammation >> SOCS3 >> leptin resistance >> obesity

The point is: I think labelling obesity as a disease is closer to the truth than it not being labelled as a disease, but I see obesity more like a symptom rather than a disease.  Paul Jaminet once made a comment along the lines of ‘calorie restricting your way out of obesity treats the symptom (excess weight) but not the disease’**.  If you want to treat obesity then brainstorm and target the underlying causes.

* By the way it’s generally: obesity >> insulin resistance, not the other around

** In a way this is similar to going on a low carb diet for type 1 diabetes.  Sure, you’re post-prandial blood glucose is normal, but your pancreas still doesn’t produce insulin.  The difference here being that you can reverse obesity but perhaps not type 1 diabetes past a certain point

The Feedback

From what I’ve seen some critics of this decision are CICOers and low carbers, but no doubt many people who think food reward is the dominant cause in obesity would be against this decision as well.  Which isn’t surprising, simply because these models of obesity are where obesity is caused by too much food, too many carbs or too much hyperpalatable/rewarding* food.  Particularly in their most simplified versions each case doesn’t lend itself towards discussions related to disease or underlying pathologies as we commonly think of them: such as organ/gland atrophy, immune dysfunction, etc.

The motivations behind the decision are likely financially motivated and people are right to anticipate new/more drugs and surgery for people with obesity, which probably will lower an individual’s sense of responsibility.  But arguing against the truth (assuming for a moment it is) for the sake of increasing other people's motivation to lose weight is an error Walter Willett made recently.  I bet some people who are against the labelling of obesity as a disease (purely on the grounds of drugs/personal responsibility) are probably also critical of Walter Willett's actions, which is a double standard.

* There is a difference between palatability and reward.  Palatability = tastes good.  Reward = promotes further consumption

Will Things Get Better

As for the question of: will classifying obesity as a disease make things better or worse?  I’m sitting on the fence.  It’s one of those questions that no one could know the answer to, and one where people can make reasonable arguments for each side of the debate, for example:

  • Good: people stop treating obesity as simple CICO and get serious looking at underlying pathologies that may be causing their obesity and hindering their weight loss attempts.  People stop being blamed for obesity 
  • Bad: pharmaceutical and surgical options become more available and people feel powerless to reverse the 'disease of obesity' (replacing blame with hopelessness), which both lead to poor diet and lifestyle choices and more money spent on drugs/surgery

Even if drugs come onto the market is that necessarily bad?  Sometimes drugs can have an appropriate therapeutic target and actually change the course of a disease.  I’ve noticed that some researchers are looking into PTP1B inhibitors*, which could reduce leptin resistance and insulin resistance.  If the goal is to improve people’s health, improve their quality of life and reduce healthcare cost and if there’s a drug that would do that with minimal side effects (because most people aren’t going to make a major dietary change), then isn’t that a good thing?

* I haven’t noticed anything for SOCS3 inhibitors, which might be because a major function of SOCS3 is to negatively regulate pro-inflammatory cytokines

Further Reading:
(1) Overweight but Insulin Sensitive and Normal Weight but Insulin Resistant: Part 1
(2) Leptin Resistance
(3) Top Science Journal Rebukes Harvard's Top Nutritionist
(4) Is Obesity a Disease?

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