That example is pretty much my history.
In highschool I topped out at about 285. At 6'1"-ish and stocky I was about 35-40% bodyfat. When I got down to about 180 at my thinnest, I was working out twice a day, living off of smoothies, sugar free tea, and meal replacement bars. The moment I began reintroducing normal foods (not junk, just recommended daily value sort of stuff) I started gaining back weight. I started going to the gym only 3-4 days a week and I started gaining it back quicker. Compared to my friends I was eating far less, and working out far more, and I was gaining weight. Diet and exercise DOES work, but I was not particularly interested in maintaining a lifestyle that meant denying myself all of my favorite food and spending 10-15 hours a week in the gym. I settled into a weight around 230-240 a few years ago and it appears that is where I will stay unless I pick up that gymrat life again.