Food Choices and Caloric Density
1) It's pretty crappy eating bland food. Food is one of the joys in life.
2) Sticking to a particular way of eating requires willpower - hunger and cravings will weaken your resolve.
Take two different diets (Let's pretend for the sake of argument that they contain the same number of calories and the same amount of protein): Diet 1 is icecream, chocolate and pizza; Diet 2 is vegetables and lean meat / vegetarian alternatives.
It doesn't take a genius to realise that the food in Diet 2 is going to be a LOT more filling than the food in Diet 1 - i.e. it's going to take a lot of vegetables before the calorie limit of the day is reached, but only, say, half a pizza.
One of the things I've come to realise on my food / nutrition / body recomposition journey is that the foods we have available to us are extremely calorie dense, but because they are now so abundant, we treat them as the norm. Things like potatoes, pasta, rice, cereals are assumed to be "healthy" or "normal" because we grow up with them all around us. The problem is, our biology developed during a time before agriculture. We were hunter-gatherers and, biologically speaking, still are. Foods like starchy carbohydrates would have been a minor part of our diet - a rare treat. The opposite is now true. The bulk of most people's meals are carbohydrates. Please do not misinterprate my message here - I am not saying that carbohydrates are bad. What I am saying is that the food we take for granted is extremely rich and calorie dense. It doesn't fill you up that much, but provides a lot of calories. It's no wonder people struggle to keep their weight down. It's just assumed, and of course some companies like cereal manufacturers are only too happy to further this myth, that cereals and pasta etc. are somehow healthy choices.
I truly believe that if we are to overcome the "obesity epidemic", we need to realise that the modern diet is not normal relative to our bodies. We place far too much emphasis on the starches and far too little on vegetables and protein. The ideal diet is one that consists almost entirely of as many different vegetables as possible, with generous servings of fish, chicken, turkey (or vegetarian alternatives). Foods like rice, potatoes and pasta should be viewed as minor components or treats and used sparingly. Dairy is an excellent food for providing both calcium (especially important for women) and protein, but care should be used with many products, such as cheese and butter. It's all too easy for them to be high in fat. Skimmed milk and cottage cheese are ideal in this respect, since they contain all of the protein and calcium but very little fat (again, I don't wish for this to be interpreted as "fat is bad", simply that fat is extremely calorie dense and should therefore be treated with caution).
This has turned into more of a rant that I had intended (I may come back and clean it up later), but this idea of caloric density was something of a eureka moment for me. When combined with the fact that, as a species, we are very adaptable/impressionable/programmable and tend to assume that whatever environment is presented to us when becoming adults is the norm, food choices like cereals are assumed to be ideal.
Practical advice from all of this? Check the food labels and choose foods that have as few calories per 100g as possible. e.g. Berries were one of my recent "finds". I simply assumed they would be calorie-dense. I now regularly help myself to piles of frozen raspberries / blueberries. With only ~30 calories per 100g, you can happily pig out on 500g of them at a time! They go great with cottage cheese or low fat yoghurt. I also feel I must thank Martin Berkhan of LeanGains (check the links to the right) for this tip.
Further disclaimer - this post is mainly intended for people who wish to lose fat. Of course for those who wish to gain muscle, excess calories are required and food choices should be changed (i.e. caloric density of foods would be increased when trying to gain weight).