She quotes How to Get Your Kid to Eat: But Not Too Much, by Ellen Satter MSW, RD. Check out this passage:
Definition of ‘Normal’ Eating
“Normal eating is being able to eat when you are hungry and continue eating until you are satisfied. It is being able to choose food you like and eat it and truly get enough of it – not just stop eating because you think you should. Normal eating is being able to use some moderate constraint in your food selection to get the right food, but not being so restrictive that you miss out on pleasurable foods. Normal eating is giving yourself permission to eat sometimes because you are happy, sad or bored, or just because it feels good. Normal eating is three meals a day, most of the time, but it can also be choosing to munch along. It is leaving some cookies on the plate because you know you can have some again tomorrow, or it is eating more now because they taste wonderful when they are fresh. Normal eating is overeating at times: feeling stuffed and uncomfortable. It is also undereating at times and wishing you had more. Normal eating is trusting your body to make up for your mistakes in eating. Normal eating takes up some of your time and attention, but keeps its place as only one important area of your life.”
“In short, normal eating is flexible. It varies in response to your emotions, hour schedule, your hunger, and your proximity to food.”
Satter, E. (1987). How to Get Your Kids to Eat: But Not Too Much. Bull Publishing. ISBN 0915950839.
I like this definition because its flexible and recognizes that everyone will over or under-eat at times--there isn't that magical perfect eater totally in touch with one physiological needs alone, devoid of interest in food from a social or conditioning position--we are social creatures, and social eaters. And sometimes we are lonely eaters, etc. Read the whole post if you're interested.