I remember an interview with the guy who invented the Twinkie. Discussing the filling he noted: 'It's made of lard and powdered sugar, all natural, nothing wrong with that'. The problem with Twinkies, and other fast foods, are that they contain a lot of calories in a small package so it is very easy to exceed the calorie needs of a normal, low energy, westerner.

Eaten quickly, and until you feel full, you can easily double or triple your caloric requirements. Do that frequently and you will gain weight.

The lesson I took from it ties in well with what our evolutionary ancestors did. Our ancestors didn't know beans about vitamins, balanced proteins, or ratios of fat/protein/carbohydrates. Performance may not have been optimized but the human body can make due with just about anything.

If the central goal is losing weight the key is to limit calorie intake. Worrying about getting food-group ratios just right and diddling around with micro-nutrients are both largely irrelevant.

That is not to say you won't feel better with some casual attention paid to the niceties of vitamins, roughage and leaning on vegetable products. Fact being that dieting is a lot easier using a lot of leafy greens. They have such low calorie counts for any set unit volume means that you can much more easily feel full while staying within caloric limits.