It is interesting to know that he loses his weight not because of some diet pills that burn fats when he eat junk food. It is essentially redefining what he wants that get him to lose so much weight.
His regime goes like this. He eat nothing but baked/boiled potato for 2 weeks, only eating when he is hungry. This fundamentally changed his eating habit.
After 2 weeks, whatever healthy food that use to taste blend will become tasty to him as his taste bud felt the change in flavor.
After months of eating only healthy food, no meat product or unhealthy fats and carbs. He have stop having craving for junk food and even find them disgusting. Now all he want is healthier food.
This is redefining what you want to achieve your desire goal. We can use the similar regime to help us achieve our goals by redefining what we want.
Maybe you goal is to save some money and the bad habit that cost you a lot of money is eating out too much. You can maybe start packing your lunch to work and cooking your own dinner for 2 weeks. You may start to feel the change in habits and soon enough after a few month you might not like to eat out as much. You WANT to cook your own meal.
There are many way to apply this method but you must have the will to change your habits. Once that is done, you can achieve any goal by doing whatever you want.