Is Obesity a disease? If so are there any documented studies about it?

That is a question still under debate. Here are some of the discussions:

http://www.ur.ku.edu/News/00N/SeptNews/Sept12/obese.html

What's a disease? According to Merriam-Webster...

"a condition of the living animal or plant body or of one of its parts that impairs normal functioning"

so, I'd say that obesity is a disease, since it is a condition that impairs normal functioning (i.e. running, walking, swimming).

Does it make a difference? Some people would think that a 'disease' means it's 'not their fault'. (This is different to a medical condition where the result is excess weight. Choosing to eat too much is, in my book, the same as choosing to smoke... The calories are addictive... and is not the same as a condition which you cannot influence by your personal choices - however hard those habits may be to kick- it's still a choice).

Adi, obesity is not a choice for everyone, although it is for many. Eating too much is not the reason some people are fat, the same way as eating too little is not the reason some people are little.

I have read that there is speculation that a virus causes obesity?

I have also read that once a person is substantially overweight, that person can very quickly gain more weight by eating just a little bit extra than a person of normal weight by eating just a little bit extra. For example, if Jane is 50 lbs. overweight and so obese, by eating 150 calories extra per day, Jane might gain 10 lbs., while someone of normal weight doing the same might gain only 6 lbs. Life is not fair, and it seems that the body works differently than had ever been known before.

Obesity has been declared an epidemic, and cases of diabetes are expected to skyrocket--along with health insurance premiums. Around 2/3 of Americans are overweight or obese. Uncle Sam recognizes obesity as requiring tax deductible health care in, I think, most situations. Read about obesity when you see an article about it.

In my opinion it is just like my under eating is too. I have a very hard time getting weight on and not eating. So this is a disease right? Then how can over eating NOT be?