The thing is on another day fruit and yoghurt wouldn't have been substantial enough at all and I'd need a bigger lunch. This is because how much and what you should eat at any given time all depends on hundreds of factors ... how much sleep you've had, how much water you've drunk, how much fruit and veg you've eaten (if you don't eat enough your body will keep you hungry to increase your intake of vitamins), how active you've been, how much stress you're under, if you're fighting off a cold etc etc.
So when I hear of people following a strict diet which tells them exactly how many calories to eat, or what to have in each meal every day it frustrates me. I'm all in favour of guiding people and suggesting healthy options, but no-one can possibly know what your body needs at any given time more than your body itself. The key is just to listen to the cues. For example the other day I had a very healthy lunch with rice, vegetables and some pulses. However at the end I felt distinctly unsatisfied - full in my stomach but also definitely needing to eat more. So I tuned into that feeling and thought about different foods I might like and through that realised that my body was craving protein.
I went straight down to the health food store to grab a bounce ball and a Sojade yoghurt and immediately felt alot better having eaten them both - no diet plan could have told me that was what I needed at that moment. Obviously if you find yourself craving Oreos or Ben and Jerrys that isn't a cue you should be following! But by tuning into your appetite and paying attention to foods you're attracted to you are much more likely to give your body the nutrients it needs to feel satisfied and for optimal health.