The HCG diet uses the power of human chronic gonadotropin along with a low-calorie diet to change your metabolism. Based on the research of Dr. Simeon’s, the HCG diet has been studied extensively over the last 60 years and is safe as long as it is medically supervised. When used combined with a low-calorie diet, HCG injections appear to influence the metabolism, increasing energy expenditures during dieting. This can lead to weight loss in traditional stubborn areas, including the belly, thighs, and chest. Most people can expect to lose around 20 pounds in 40 days.