What is Obesity?

DISCLAIMER: I am NOT a physician. I provide sources for my text so you can see where I'm getting these ideas. Any medical advice should be obtained from someone with an MD and a background in studying or treating obesity-related disease.

Obesity is defined as an excess of adipose tissue (Obesity Society) most commonly estimated using the Body Mass Index system, or BMI. Technically, overweight just means you weigh too much according to whatever scale is in use, but it is often used to indicate someone who weighs too much but not enough to be considered obese.

Your BMI is calculated using your height and weight to determine a ratio that can then be categorized as underweight, normal, overweight, or obese (with newer categories such as morbidly and super obese gaining recognition). The BMI table was changed in 1998 by the National Heart, Lung, and Blood Institute to reflect recent research showing previously considered "normal" weights could increase risk for obesity-related diseases (source). Morbid obesity was recently added to indicate extra health risk for someone who is 100lbs over a healthy weight or with a BMI greater than 40.

NOTE: It is important to remember that a BMI classified as "overweight" or "obesity" does not indicate a person has excessive adipose tissue. Athletes, for example, commonly have muscle mass that puts them in these heavier categories without the increased health risk attached. It is important to be mindful of one's own body and lifestyle when using the BMI tables or estimating obesity. BMI is a quick and easy way to look at where a person stands numerically, it is not a diagnosis or a be-all-end-all measure.

In addition to the numbers, obesity has several hormonal changes associated with it. These include insulin production and catecholamines. Insulin production by adipose cells may increase as the cells increase in size, contributing to insulin resistance and type 2 diabetes. Catecholamines are part of a stress response and respond differently in obesity that may lead to increased sympathetic nervous activity, which can lead to hypertension. Hypertension is a risk factor for atherosclerosis which can lead to CVD. See Kokkoris and Pi-Sunyer, 2003 for more regarding obesity and endocrine disease.

So, we can see that obesity can be unhealthy in a myriad of ways. It may not directly cause CVD, diabetes, or other health issues, but it can be related to them. It is considered a risk factor, meaning it is a red flag for physicians to check for presence or increased risk of other health conditions.

In the past decade or so, more research has found a sub-group of obese individuals since labeled "metabolically healthy obese individuals" or OBMN (obese, metabolically normal) by Sims in 2001*. Some other acronyms have popped up but "metabolically healthy" is the key phrase. I'll go more into this next week, but the debate about what it means to be metabolically healthy and obese, if there are still risks or other health issues associated with it or what the social ramifications are for metabolically healthy obesity.

See you next Monday for more on metabolically healthy obesity!

Cheers,
J. G.

* Correction: The concept of metabolically healthy obesity was first described in 1980 by Reubin Andres.
Andres, R. (1980). Effect of obesity on total mortality. International journal of obesity, 4(4), 381.