I run before breakfast too, but mine is high intensity where I aim for at least half my run at maximum heart rate and the rest cardio rate. Plus warm up and cool down walks at fat-burning pace. I come back literally dropping with sweat.
I think I must just not eat fat-rich food. My milk is semi skimmed and my plain yoghurt is fat free. I don't eat much cheese so I guess all my diary is low fat - this wasn't conscious, it's the same as I've always bought.
I rarely fry anything so don't need oil. If I need to brown meat or soften onion (for example) I do so in a nonstick pan so no oil is needed. I dry-roast veg, so again don't need oil.
We have a couple of quorn meals a week. We're not vegetarian but quorn is a great low calorie protein source and the children like it. So that reduces fat. Aside from that we mostly have chicken or white fish, so quite lean.
I used to have very low carbs, with only the carbs from veg. But as my running increased (I now regularly run 10k at a high intensity rate) I recognised I needed dome carbs. But only have whole grain, non-starchy carbs (oats and rice). No bread, pasta, or thinks like cake, biscuits etc.
My protein is artificially high, compared to the real food I eat. Aware that I needed more energy to run and not keen to eat too many carbs, I started using protein powder. It's the lowest calorie way to increase protein that I can find. 114 calories for 25g of protein, for the brand I use (and chocolate flavoured, so even better).
I have 1 portion of protein powder mixed with my warm porriage oats after my run every morning. I also sometimes have chocolate protein powder mixed with natural yoghurt and soft fruit as a pudding 2 or 3 times a week. A healthy way to get my chocolate fix while also boosting my protein levels.