In fact, you CAN make generalizations because there is plenty of data showing the vast majority of people who diet fail at keeping the weight off long term. This may be because most diets are crap, or it may be because changing metabolism is a Herculean task, but the Slate article raises valid points. It's uncommon to succeed at weight loss...that's an established fact. Why, we don't know yet. It may well simply be a product of our modern western food environment, i.e. sugar, processed grains, too many carbs, seed oils and/or overabundance of food and/or lack of daily exercise....all conspiring against most of us. Eighty percent of adults 50-60 are overweight - are they all undisciplined or don't care?