I do think that there is a clear difference between 'I should cut back on the cakes'-type overweight, and 'I have inadequate control over my eating'-type obesity.
It's not as simple as 'eat less', 'put the fork down chubby' or 'get out and run/lift/whatever'. I have trouble with controlling my appetite, and I have issues with knowing when I should stop eating (it's quite hard to hold back when every body signal indicates you are still very hungry).
In my view obesity is a disease, but it's false to think of it as being like the 'flu. It's a chronic issue, like high cholestorol, blood pressure or a peanut allergy. There are environmental factors and behavioural reasons why it is a health risk, but the underlying cause has a physiological source.