Children! I have 3 kids and work from home, so meals are scheduled. I try not to feed them junk so I end up eating healthy. Chasing my toddler probably burns a lot of calories. Also I am on the phone a lot for my work so I always make sure I pace back and forth any time I'm on the phone.
Really though I think life just keeps me slim. Taking care of the kids, garden, walking the dogs, staying busy, and eating home cooked meals all contributes. I thought about writing a hub about this. I may be back to make a hub about it.