If you don't have faith that you can and will lose weight, then you can't and won't lose weight. Faith is a scientific as well as spiritual principle. It's spiritual in the sense that it can't be perceived by the five senses. For example, you can see the effects of wind blowing but you can't see the wind nor what's causing the wind. Faith is scientific in that there's a particular method by which faith causes the effects you want based on how the mind is structured or how it works.
If you know how the mind works, you can then have a reality-based faith that it'll produce the results you want. -- But then it's no longer faith or belief; now it's a knowing. You know it's going to work just like you know two plus two equals four. All you have to do is know and apply the method.
So, how does the mind work and what's the corresponding method? The first thing to understand is that what we're talking about here is self-control. We weren't designed with marvelous physical, mental and emotional faculties without the means or method of controlling them. That wouldn't make any sense at all. You wouldn't have arms and legs and not be in control of moving them in virtually any way you want to move or use them. Likewise, you wouldn't have thoughts and feelings without also having the means by which to control those thoughts and feelings. Same with your appetite. You couldn't have an appetite without also having the means to control it as well.
The second thing to understand is that your overeating is a habit, and all habits -- good, bad or neutral, are located in the subconscious part of your mind. And the only way to treat something that's subconscious is to separate yourself from the thing you're habituated to. Your habit is a mental and/or emotional attachment -- to food in this case, and the opposite of attachment is detachment.
So the solution or method is to mentally and emotionally detach yourself from the food you're eating, while you're eating it. You and the food are not one thing, but are two separate entities. The method is about keeping the two separate. Keeping them in their respective positions. One as just provider of fuel to live, the other as just consumer of fuel to live. Everything else is secondary -- such as how good it tastes, looks and smells, how nutritious, the amount of fat and calories, etc.
Separating yourself from food in this way gives you the clarity to know whether you're eating for the right or wrong reason, to know when the body is sated, and the power to effortlessly stop at that exact point.
This is The Law of Detachment Weight Loss Method