Watch what you eat and how much you eat and how many calories you eat

This part is important as well. People forget the great majority of food stuff has calories in it and that it counts in the end. Herbivores the size of elephants are able to sustain themselves on plants, frugivore animals can get fat on too many fruits. Some people think you can stuff yourself silly on "healthy" food and have it all figured out, when in the end they might get all the vitamins they need, but they'll still be ingesting too much food and too many calories.

I know someone who went on a diet and while she lost some weight at first cutting off soft drinks and sweets, she plateaued fast and can't seem to lose more. And yet she keeps snacking all day long on dried fruits, granola bars, and nuts of all kind. She won't understand how even healthy snacks have calories in it. She thinks the nuts' oil and the fruits' sugar do not count.