Is walking on treadmill @ 4.0 mph 30 minutes a day everyday....?

(2 15 minute miles) enough to maintain weight. i also strength train 3 times a week. i eat 95% healthy everyday, drinks lots of water, never eat fast food, never eat fried food, and never eat salty things like chips yuck! rarely eat over 40 grams of fat a day. but i do eat some hershey kisses and twizzlers and gingerbread cookies as a snack at night.