Doesn't your body type affect this a lot? http://www.muscleandstrength.com/articles/body-types-ectomorph-mesomorph-endomorph.html
Luckily I'm a mesomorph, maybe slight lean towards ectomorph. Never had problems with gaining weight regardless of what I ate growing up and am fairly toned despite little exercise (only swim). Despite this I've been trying to eat a lot healthier for the last year or two as I imagine my insides are horrible lol
Good luck to all the people in here looking to get fitter! I know very little about fitness, but I've found swimming regularly to be a lot more fun than other exercises. Maybe finding an exercise you enjoy will help keep you motivated in the long run.
It's summertime, and the house AC is busted. Working out when it's 85 degrees INSIDE seems dangerous, so I've gone a bit lax. Losing weight on the other hand is easy for me, since putting on weight was the hard part and I can easily just go back to my regular eating habits.