The willpower is the difficult bit and is the reason most people spend money on diet plans and exercise classes. Everyone knows about “eat less, move more” but actually doing it is not that simple if you have crap willpower (I do!)
Free things that have helped me with willpower:
Couch 2 5K. It’s really good for willpower IME because you follow a set programme where you are meant to go for 3 runs a week. If you skip one then you find it harder next time. If you follow the programme it really works which is rewarding. There is also Couch 2 Fitness (also free) which is video exercise classes rather than running, but I haven’t tried it.
Not buying things I tend to snack/binge on. For me it’s biscuits and nice bread. So I don’t buy these unless it’s for a specific meal/visitors, just sandwich bread for the freezer.
Make myself have a glass of water or cup of tea if I feel peckish. Often I’m actually thirsty not hungry.
Go to bed earlier so I don’t do midnight snacking.
Buying more veg so I have to eat them before they go off (I really hate binning food)
Basically work out where YOUR willpower weaknesses are, and then work out fixes for those.
Remember most of losing weight is about what you eat. Exercise important for health but only a small element weight wise.