You might not be overeating at all. Tuna and vegetables have a lot of volume but less energy than pasta, soda, etc. Folks who are naturally lean tend to eat more frequently and more carbohydrate so I would be unafraid of potatoes and possibly rice and peas.
If the appetite is intrusive I would plan proper meal courses, e.g.:
soup/salad -> protein/starch -> fruit/fat
Looking forward to that is better than drifting from one snack to the next IMO.
Lots of: urban hiking, cycling, sprinting
Lots of: fresh meat, seafood, eggs, organs, tubers, starch fruits, vegetables, meat fat, dairy fat, oil fruits
Some: cured meat, dairy protein, sweet fruits, rice, pulses, tree nuts, oil seeds
Minimal: soy, refined proteins, sugar, liquid carbohydrate, grains, refined oils, peanuts