Early 2013 worldwide obesity had nearly doubled since 1980;
7 over half a billion adults and 40 million pre-school children were
8 obese. Shockingly, overweight and obesity nowadays kill more
9 people worldwide than malnutrition does (WHO, 2013). This Q3 huge
10 threat to human health has provided an impetus to the research on
11 body weight regulation and energy homeostasis. Energy homeo-
12 stasis requires an accurate match between energy intake, i.e. food
13 intake and digestion, and energy expenditure, i.e. basal metabolic
14 rate, physical activity and thermogenesis for endotherms. A key
15 hormone coordinating this balance is the almost two decades ago
16 discovered hormone leptin, named after the Greek root leptoz
17 meaning lean