Weight gain induced by medical regimens can be really hard to put off, and YES, this is something that happens (it's not ultra-rare as fitness extremists want you to believe). People's bodies react differently to the heavily-processed, specifically-engineered food we have. It is true that most people can regulate their weight with enough effort, but the amount of effort required seems to fluctuate greatly based on hereditary factors.

This doesn't even mention that in America, it's almost impossible to find food that isn't packed with junky addictive substances. It's pretty likely that normal people who are consciously forgoing the "candy" in attempt to stay healthier are getting practically the same amount of junk calories from bastardizations of "healthy" foods, like "natural whole wheat" bread that contains brown sugar or "maple syrup" that is actually just HFCS, water, and dye.

The issue of obesity is much more complicated than a lot of people want the populace to believe. Identifying the motives behind the perpetuation of this confusion is left as an exercise for the reader.

I believe the issue is caused by the technology we have (along several fronts, including but not limited to the sedentary lifestyles promoted by office work, and the way we manufacture foods today, which does not agree with the biological makeup of many in the population) and I believe there is a technological solution to it out there somewhere. Cheers to the MIT team for looking into this and not just sticking their head in the sand.