" When researchers have measured seasonal variations in insulin levels in humans, they have invariably reported that insulin is highest in late fall and early winter—twice as high, according to one 1984 study—and lowest in late spring and early summer. Moreover, as the University of Colorado’s Robert Eckel has reported, lipoprotein-lipase activity in fat tissue elevates in late fall and decreases in spring and summer; its activity in skeletal muscle follows an opposite pattern. This would stimulate weight loss in the spring and weight gain in the fall, whether we consciously desire either or not, and would certainly make it easier to lose weight in the spring and gain it in the fall. "
― Gary Taubes , Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease