Food science is just crazy. Too much pseudo-science. All those fancy diets, not mixing carbs, fats and proteins in one meal, the current superfoods ("it's all you need!") - it just doesn't make sense.
I've never limited the amount of food I take, though I generally try to go for natural and avoid processed food. I cook my own dinners at home (most days), and make sure there's vegetable included as well. Snacks are often fruit (fresh or dried), rather than crisps or biscuits. Another thing is that I try to keep my diet varied, eating many different things. All this should ensure I get all I need, in sufficient quantities, and in the meantime I can really enjoy what I'm eating. It seems to work really well, without much thought (or worries) about it I do keep myself in shape. I've lost quite some of my waistline over the past year, in part due to my current job as tourist guide which means I'm walking a lot - easily 8 hours a day on my feet, for several days a week.
The problem for most people nowadays is most likely 1) lack of movement, and 2) lots of processed foods (high nutrient density - doesn't make you feel full nearly as fast as natural food does).
Many people nowadays sit in their office all day, then sit in the car going home, pass by a drive-through restaurant to pick up junk food and sit in the car eating it (this part for the Americans typically), and sit on the couch most of the evening watching TV before going to bed. No walking. Not even the walk to the train station, no sports, no physical exertion ever. That's asking for problems. People are designed to be active, to walk around all day, construct things with their hands. We're designed to handle natural food sources which by nature are unprocessed and very varied: there's simply a lot of edible things around in this world.
This is why I got to my rather simple philosophy of remaining active, eating varied, and basically eating as much as you like when it comes to unprocessed foods.