Four important fundamentals for naturally lean living:
1 Always eat when you are HUNGRY.
If you don't eat, you don't shit, you don't shit you die (is what my Dad always said)! But know what hunger is. It's not a feeling of boredom or fear or stress or anxiety. Know what it feels like in your stomach. You won't get it right all the time but over time it will get easier.
2 Eat what you FEEL like.
Yep, if you want to eat chocolate and lollies all day long then do so but remember number 1, you're only eating them when you are truly hungry. The mistake people make with this guideline is that they think they'll eat unhealthy food all day long every day but I'm pretty sure even I would get sick of chocolate and lollies if I did this. It's not natural instinct to live on this food and eventually you'll crave meat and veg for example.
3 Eat CONSCIOUSLY and MINDFULLY.
Use all your senses and enjoy every single mouthful. Feel the flavours and delight your senses. Get that party in your mouth happening.
4 STOP eating when full.
You've done it before. It may have been a long time ago but you have done it. As a baby, a child. When your mother tried to get you to have more breast or bottle you spat it out or wouldn't take it. As we grew older we learned to overeat, binge, stuff ourselves stupid. Whatever we learn we can unlearn.
Of course, there are many more variables to this, but here's an excellent place to start. You might like to head over here for a more detailed rundown.