Combination of things.
Mon-Fri I eat as healthily as possible, by that I mean no chocolate, crisps, ice cream, wine etc. Sat/ Sun I eat what the hell I want, and that does often involve a cream cake/ chocolate and lots of wine.
Mon- Fri I do 16:8 fasting so only eat between 11am and 7pm. This at first helped me drop a few lbs, now it helps me maintain. It also helps me be able to eat shite at the weekend and not put weight on.
I don't buy shite (Mon-Fri) so it's not in the house. I live rurally so would have to drive 10 mins to the nearest shop, park up etc if I really decided I wanted that chocolate bar and quite frankly I can't be arsed.
I like to be active, I try and get my 10,000 steps in a day through walking the dog and I run a couple of times a week too, also horse ride 3-4 times a week.
But yeh, tbh it is willpower. If I had a house full of sweet treats....I'd eat them, simple as so I have to not have them in the house and look forward to the weekend for them.
Having said all the above, I do have whatever I want for dinner Mon-Fri (except have a takeaway, I won't do that) but my dinner's definitely aren't always healthy, but the fact I don't eat crap throughout the day and do my fasting balances it out.
It's a concentrated effort, but really not much of one. I'm 8st4lbs, a size 6-8 on top and 8-10 on bottom, so it does help me stay fairly slim so for me it's worth it.