I'm female, 55 and was not fit, though I used to be in my 20's. After two kids and 30 lbs of slow slide into middle age I was ready to find a way out but nothing had worked much. I'd done most of the standard recommended programs. It helped some. I wasn't a couch potato but hardly what I'd consider fit.
2 years ago I ran across Slowburn Fitness and started doing it. I was SO grateful for something short, simple and effective. 2 years later I'm as strong (or perhaps stronger) than I was in my 20's. I have endurance and stamina. I also have lost 30 lbs and am down to a very good body mass figure. And ALL of this with two 15 or 20 minute sessions a week. I couldn't believe they meant it but they did.
The people who write negatively about this program say that its hard to do or it "hurts" and so people wont want to do it. I found just the opposite. I was SO glad I could do it at home, virtually for free, and not have to be at a gym (though later I've come to use gyms sometimes.) I was SO grateful that it was working they way the authors promised. And I can't believe that it really delivered what it promised, but it did.
So get it and do it! It is the least dangerous, safest and most effective program --especially for us older types for whom injury during exercise is an issue. Just be aware that you do not have to HURT to do this, just work out till your muscle fatigues. The exercises are designed to fatigue muscles fast, in only a few repetitions. If you are not used to the feelings you might consider them unpleasant but. . .just remember, its ONLY FIFTEEN MINUTES. (twice a week at that) and you get as much fitness or more than if you were spending hours doing other programs.