Answer:
D
Step-by-step explanation:
Obese humans already have high levels of circulating leptin
Leptin is a hormone secreted from fat cells that helps to regulate body weight. But in obese people they have unusually high levels of leptin. This is because in some obese people, the brain does not respond to leptin, so they keep eating despite adequate (or excessive) fat stores, a concept known as ‘leptin resistance’. This causes the fat cells to produce even more leptin.