My weight has fluctuated soooo much. Part of this is because I'm a girl. Part of it is because I am somewhat messed up in the head and it effects more some times than others. Since I hit my "adult height," my weight has varied as much as 70 pounds in 18 months.
The one thing that has always been true?
I HATE the gym.
I will go. In fact, I reached my healthiest and fittest last winter because I went at least 5 days a week and stayed for 45+ minutes at the ellipticals/treadmills and the weight room. Unfortunately, the second something messes with that routine, I drop it and drop it hard. Within a couple weeks I gained back the 10-15 pounds I'd lost to get there, and the muscle definition degraded.
My ideal is nature: hiking, walking, biking, horseback riding, swimming. I like playing sports, too. I just really, really hate the gym. I think it's mainly the need to go to one place to do one specific thing for a ridiculous amount of time for a non-immediate benefit. It needs to be fun or provide photos or stories or an end goal or something because I just can't continually live off of the promise of it doing something in the long run. Lame, I know. Whatever.
The funny thing? If I had a treadmill or weight set at home, I'd work out every day. Guess I'm just lazy at heart. :p