So far we have discussed the high prevalences of obesity and diabetes and their adverse health consequences. I did not mention the extraordinary adverse economic consequences for both individuals, their families, and the society at-large. This is an important subject, which I will discuss later. In this entry I will move into the sometimes murky world of causation. Up to this point, my comments are based (mostly) on firm scientific data and are not really controversial. I want to start by focusing on obesity and leaving diabetes until later. For now, it is enough to know that type 2 diabetes only rarely occurs without concomitant obesity, even though diabetes is mostly genetically-based.
Endocrine Disorders and Obesity
It is well known that several endocrine gland disorders are associated with obesity. I chose the term “associated” rather than “cause” since obesity can be prevented no matter what, if the individual’s caloric intake is equal to or less than caloric expenditure. Hypothyroidism “causes” obesity by decreasing the caloric expenditure side of the equation. Cushing disease and syndrome, conditions in which levels of the natural hormone cortisol or a related synthetic hormone are elevated, also cause obesity. The mechanisms include increased appetite and altered fat metabolism with deposition of fat in the neck (the so-called “buffalo hump”) and the abdomen. Hypopituitarism with growth hormone deficiency also causes obesity. Here the mechanisms are not well understood but growth hormone deficiency does alter fat metabolism and is often associated with hypothyroidism.
In growing children it is quite easy to tell if an endocrine condition is responsible for the excessive weight gain; each of the 3 conditions mentioned above are associated with poor growth in height.
Miscellaneous Conditions Associated with Obesity
Many other medical conditions/situations are associated with obesity. In some instances, the mechanism for the obesity is known; in most instances, however, the cause and effect relationship has not been well established. For example a number of syndromes, medical conditions described by either the name of the person who discovered the disorder or a name that conveys the most important features of the disorder, are associated with obesity. Many syndromes are not even specific medical disorders, but rather, patients grouped by having certain signs and/or symptoms in common. Examples include the Turner syndrome and Prader-Willi Syndrome. Both of these disorders are now known to be caused by specific chromosomal abnormalities. The specific reasons for the associated obesity are not well understood. Other disorders frequently associated with obesity include Lawrence-Moon-Biedl syndrome and pseudohypoparathyroidism.
Certain drugs are also associated with obesity. In most instances, the mechanisms are related to increased appetite. Examples include some psycotropic drugs, drugs used to treat allergies, and marijuana.
Finally, obesity is associated with any condition that restricts physical activity.
What Else Causes Obesity?
Unfortunately, the conditions discussed above explain only about 0.1% of all cases of obesity (I just made up that number- I don’t really know with any accuracy what the percentage really is, but it’s very low). What about the other 99.9%? I’ll discuss that in my next entry. I’ll give you a hint- think genetics and environment.
- Obesity and Type 2 Diabetes: What’s So Bad About Being Overweight?
- Obesity: What Do Cars and People Have in Common?