OT: Question on HIIT Training

Honestly, as someone that's been there and still working out of it, most important thing is to improve your diet and do something (almost anything!) relatively intense that you'll do regularly.

If you're really out of shape, any regular exercise is probably an improvement. That's part of why things like cross fit are so popular. It's not the best way to optimize muscle mass gain for someone lean or anything like that, but it motivates people to show up and if you start from a low level of fitness you will definitely get stronger and fitter, at least at first.

Also from experience, I'll say that getting some coaching, whether from group classes, a personal trainer, or just a knowledgeable buddy, is worth it. Injuries suck and downtime kills your progress, so make sure your form is good. Exhaustion and discomfort are good, pain is bad - if something really hurts, back off a bit. If you try to do too much for ego, you can get hurt.

Stop worrying, start lifting.

Personally I've found that diet without exercise doesn't help me lose much weight.  When I combine the two I get the best results.  Anything that sheds weight fast isn't sustainable, better to go gradually.  Also, if you haven't lifted much before, you will gain muscle pretty quickly at first, and likely stay about the same weight but notice a body change as you lose fat and gain muscle. 

It's almost entirely about diet.  Exercise is great for other health reasons but not very effective on it's own for fat loss.  My wife is a health coach if you're interested, her mom and dad both lost ~100 pounds each on the program (in less than a year iirc).  No diet and/or exercise program works without hard work but this is the easiest one I've seen as it mails 5/6 meals a day to you for ~300 bucks a month and they don't taste bad and you are kept satiated at all times.  Most diets fail because you're starving all the time and you can't sustain that for long.