>>81724760
Only about 20% regain the weight, eating is more than just diet and lifestyle as you've put it, there is an emotional coping mechanism at play for a lot of people, something losing the weight isn't going to fix, they'd need to go to therapy to either fix their problems or find better coping mechanisms.
As far as percentages go, having only a 20% of reverting back isn't bad, I'd take that chance of being in the 80% who keep it off.