Rides for overweight unfit people?

This was my problem til recently. Was hammering myself on my commute from Woodford to Westminster every day and wondering why i wasn't losing any weight (wasn't helped by the fact that when i got to work, 'cause id hammered myself i'd need carbs) and wasn't getting any fitter (well my commute was getting a little quicker but not much).

Have looked into it in more detail, got a HR monitor (well a Garmin) and have done some long slow/steady rides keeping my HR below 80% of max. Feels weird not really being out of breath much but has made such a difference. Recently did a 70 mile loop out to Stanstead and back which was hard but didn't have cravings to stuff myself with carbs after as went pretty slow (only had a nutri grain bar while i was out). Burnt 2600 calories...

Even though I've only been doing them for a couple of weeks, doing long slow rides has done more for my fitness than anything I've done in the past 18 months, did my regular 35 mile loop 20 minutes quicker today than when i first did it 3 weeks ago while maintaining the same approx HR, plus I'm definitely losing weight. Getting a geared bike made a difference too as meant i could keep my HR down and more controlled....

Hmm are there any heart monitor and all that junk that work with Android ? I don't really want to fork out for another device.

How often do you do these rides ? I have a geared bike, but it's gathered dust tbh