I think you should start by understanding why you eat a lot.
– is it because you're stressed out?
– is it because you're in a tempting environment?
– is it because you kept a bad habit in the past?
– or is it simply because your body needs it (some people just naturally burn more calories)
Try to identify the root cause and the triggers.
Then, what is "a lot"? Is it a lot of sweet/fast food? Or is it actually a healthier mix?
I suggest in the short term to prioritize quality instead of quantity. Since you are not overweight, focus on avoiding the skinny fat trap and make sure you get a balanced diet. Have more fatty fish, nuts, organic fruits and vegetables. Eat them first before being tempted by desert or fries for instance.
Once this becomes a habit, your body will love the nutrition and you'll get rid of the fear of being fat.