We overeat because we’re surrounded by seductive, calorie-dense food that’s a great deal. The food’s high reward value increases the set point of the lipostat, though not necessarily permanently, and this further facilitates overeating. At the same time, overeating itself spikes leptin levels and injures the hypothalamus by a mechanism we have yet to nail down (likely involving diet quality in addition to quantity). These two simultaneous hits cause the hypothalamus to lose sensitivity to the leptin hormone, meaning that it requires more leptin, and therefore more body fat, to hold off the
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