Hiking is about endurance and not hammering or punishing the body. It's a sport of subtlety - one of the amusing parts of running a hiking group is watching the jocks, gym rats, runners, bikers, etc sign up and see how they do - the ones that swagger about their level of fitness are often the ones that find out the hard way, hiking isn't the same. Backpacking works the core muscles and the body in ways that they don't anticipate. I don't look like anything but a frumpy middle aged lady - but I have out hiked treadmill athletes quite a few times.

Don't feel like you have to compete with other sports. Do it because it's exercise you enjoy. It is its own thing. Let the runners pretend superiority - it's not a trivial thing, being able to hoof along at 3 mph with a backpack at 10,000 feet elevation.

I don't know if a 30 minute power hike will help you lose weight. I do know that a single day hike of 8 -10 miles once a week took 10 pounds off me in 3 months, however.