I think that a diet rich in vegetables fruit and nuts is actually the most natural diet for us, as our systems really don't cope well with the modern diet, particularly if it is processed. A bit of protein and fat can be thrown in.
Not that I particularly follow it, but we eat hardly anything that is processed, do eat at a minimum 5 fruit and veg a day - e.g. So far today 1 orange and a helping of apricots, with full fat yogurt.
Lunch is parsnip, broccoli and sugarsnap, with pork chop flavoured with chutney and cheese. Apple. Mid afternoon I tend to graze on a banana and grapes. Evening meal, salad so helping of tomato, lettuce, onion, cucumber, avocado, with smoked trout, olive oil and lemon dressing. followed by pear and easy peeler little orange. So really it is dead easy to keep to that sort of level. I dont get too precious about it, but make sure plants are added at every single meal and really you can't go wrong I think.