P001-
I like you wanted a bike to get more exercise & influenced by friends into cycling. Asked for comfort bikes, but some friends really into road & mountain bikes encouraged me to go the Mountain (mtb) route, so I actually saved money and got a Trek 820 (steel frame) mtb, which I have pedalled for 2 months - put 400+ miles on it, thrown out all the kids department-store bikes and bought a second 820 for the kids to use.
I've also cleaned up my old Motobecane Super Mirage road bike & started riding that. Liking the local bike paths here in SE Mass, riding solo & with friends, and doing 10-30+ miles every few days and I can say I'm at nearly my lowest weight in 15 years. I'm going into my 6th year as an avid sea kayaker, and enjoy short hikes, but biking is much simpler and much more whole-body exercise for the time invested.
I'm glad I went the mtb route, but I already had the old classic road bike as well. Good luck!
Peter in Plymouth, MA