I know that obesity is a very complex issue with many contributing causes, but for some people it does boil down to changing long-held habits. And I think changing those habits in a gradual way, so it's not an immediate disruption that takes the body by surprise, could be one of the keys to success.
In my classes I often compare personal finance to being on a diet. Typically when people choose to lose weight they make a snap decision and then try to change everything all at once. That can last for a little while but eventually you give in to your long-held habits and binge and blow the diet/fitness plan. However, if you make slow changes - park at the far end of the parking lot instead of next to the door, get the low-fat yogurt instead of full-fat, get the ground turkey instead of ground beef, etc. those are slow changes that don't have a major, immediate impact so you're more likely to continue them.
This is the same with personal finance. Most people who go on a crash personal finance plan "I'm going to never eat out, track every penny and cancel all of my technology" fall off the wagon. It's too much too soon and you end up feeling deprived and you splurge. If you're trying to break a life-long habit of eating out every day for lunch it's better to start slow by bringing lunch once/week for a while just to start getting into the new, better habit. Same with cutting back on other treats like coffee, drinking pop with meals out, etc. Just think about it. If you eat 2 meals out a day and get a pop each time at $2 each, that's $4 (plus tax and tip) that you could save/day just by drinking water instead. That's a pretty painless way to cut back but at the end of the year you've saved almost $1500. Not to shabby.
So basically the key to making any lasting change in your life, diet or financial, is to do it slowly and with a plan instead of just jumping in with both feet and hoping you will be able to swim.