I'd use long-terming behavior because short-terming behavior will not suit you that well (too large a behavioral distance)

I'm very willing to change my behaviour. I don't think it's impossible, and it may be even easier than lose fat...

But in any case, use the PUA stuff. Even if you can't tell wheat from chaff, will still be good for you.

So any product will do? In any case, I'll leave that for last, let's see first what a better fitness level and a more sociable environment will bring.