You can work up a couple of hundred pounds extra over an extended period of years by just adding a fraction of pound per week, which is hardly going to break the budget.
And then there are people with metabolic problems. In many cases, people who are on what would be a serious diet for anyone else will still gain weight. (My wife could give me a list of such conditions if I asked...) I have friends with problems like these, and would not trivialize them.
But strangely enough it seems that most grotesquely obese people (and people who need two seats on an airplane generally qualify) actually do like eating a lot, on a regular basis. Which is fine. Enjoy life, and may I suggest that you will find Paris singularly congenial to your tastes? However unless you can point to a specific medical condition which is causing your speific problem, don't look to me for sympathy over the results.
And somehow I feel singularly uninclined to give BryceJ the benefit of the doubt...
Cheers,
Ben