Let's say that you're having a particularly good year, and you manage to set aside a savings fund for "Emergencies Only". You swear to not touch it unless absolutely necessary.
Then, you get laid off. While you get some unemployment, it's not enough to cover your bills, so you spend the savings fund. Unfortunately, the fund runs out before you get back to work, so you're having some really hard times for a while.
Later, you get back to work, and it's just as good as before. So you start saving up, and to avoid getting caught short like last time, you save about 10% more than before, just in case.
Of course, you get laid off AGAIN, and somehow, you run out of the emergency fund this time, too. So, once you are working again, you save up even more than the last time. You also become more frugal, trying to get more for your buck. That's pretty wise, right?
I'm guessing that y'all see where I'm going with this. Your body does the same thing when you diet. It stores up a reserve, and when that reserve gets used up, it does a very frugal thing and stores up even more once times are better. It also becomes more efficient, slowing down your metabolism so that you use less energy to do the same things you did before. This is an autonomic survival strategy, folks. It's not a disease, and it's not a sin. We evolved* this way because it makes sense.
Nowadays, food is plenty in our society. We need to do less physical labor than our ancestor's ancestors, and we have more sustenance than ever before. This is not a bad thing! So why can't we accept our progress and be happy that we now have the capacity to eliminate hunger? Why do we have to guilt-trip ourselves for having easier lives than any other people in human history?
I once said that, maybe I'm fat, and EVEN IF that made me more likely to develop heart disease or diabetes (which it doesn't, but let's be hypothetical for a moment), I'm still better off than people in undeveloped nations that are starving to death or dying of preventable contagious diseases. It's a crime to focus so much time, money, and energy on battling excess adipose tissue when 30,000 children are STILL dying every single day of malnutrition and preventable disease. It's abominable and vain to complain that we'll die "early" at 70 of "overweight" when many people are still dying so young of starvation.
I propose that we focus our energies on bringing everybody up to par (that is, fed adequately and vaccinated as needed) before we continue to wring our hands about the "fat" illnesses that are really a product of advanced aging. I would like to see frivolous weight loss surgery and cosmetic surgery** put on hold until every sick person who needs surgery for real medical reasons is treated. You don't get your breast implants until every cleft palate is repaired; you don't get your stomach amputation until every bad knee is repaired.
* Yes, I accept evolution as a fact, because it is. :P Deal with it.
** With, of course, the exception of reconstructive cosmetic surgery, or cosmetic surgery needed to fix real problems--NOT "my nose needs to be perfect, and I'm starting to get wrinkles"