My father, a skinny Irishman, mentions regularly at how fast others around him eat. He eats slowly, puts his knife and fork down between bites so he savours the food in his mouth, and eats less. He eats what he wants - including cake, ice cream, pizza - but he eats small portions and eats the food slowly and with enjoyment.
I was in Madrid a month ago, and noticed exactly the same with the Spanish - they eat and drink slowly, whereas in the UK, too often people eat on the run, and drink too fast. Good food, eaten for enjoyment, and in smaller amounts, is the best way to lose weight and maintain it - why go on a diet and deprive yourself if you can enjoy good food instead (and in that I include cake, ice cream, pizza, not just wholefoods!)
If you change your mindset around eating and food, you really can have your cake and eat it!