Running! People who run often have slender figures and can maintain those great figures with their running. I have seen this time and again. Kent Altena is one of those people. Sugarless4life is another (she is on lowcarbfriends.com). I cannot be a runner. I am too top heavy for that and my knees would not take it either. I used to do a lot of ballet and unfortunately my knees can be a bit iffy sometimes, so I'm careful with certain exercises.
My eldest son is another example of a runner. He says he probably burns around 800 calories with his running in a day and would be hard pressed to eat that much extra over and above his allotted calorie allowance which is high to begin with as he is 6 foot tall. Anyway truth is Daniel is skinny and running helps him stay that way he says.
So there you have it. Significant running does certainly help many people lose weight and keep it off.