Gary Taubes suggests that obesity researchers are currently focusing on energy balance at the expense of hormonal factors (Nature 492, 155; 2012), but hormonal factors have always been an important part of obesity research.
The German physician Bernard Mohr first described human obesity associated with abnormalities of the basal hypothalamus more than 170 years ago (Wochenschr. Ges. Heilkunde 6, 565–571; 1840). In the second half of the twentieth century, a negative feedback loop gradually became evident between the hormone leptin (produced by fat cells) and the hypothalamus, which has turned out to be a crucial regulator of levels of body fat.
Since leptin's discovery in 1994, nearly 10,000 papers have appeared in PubMed on the involvement of leptin signalling in obesity.