my usual lunch is a small can tuna with lettuce, tomato, cucumber, carrot and half an avocado followed by 3 pieces of fruit which may be grazed through the afternoon. (they laugh at me at work as they say I eat fruit all afternoon). Sometimes that fills me until dinner but often about 3.30 I snack on nuts (almonds are good). so I would add the avo to your lunch occasionally and get some nuts.
But I agree that if you are not hungry don't eat. I pretty much eat the same thing 4 days a week at work and some days I am totally full and could not squeeze another thing in and some days I need the nuts. so listen to what your body is saying. good luck.