Since second half of the 20th century, the low-fat, low-calorie diet has been the primary treatment for obesity. During this period, obesity rates tripled, prompting Fung to question the treatment’s efficacy. In his medical practice, Fung observed that insulin treatments for kidney disease, notably, type 2 diabetes, caused his patients to gain weight. Obesity is also the root cause of type 2 diabetes. Despite the implications of weight on health, however, medical professionals have largely overlooked obesity, leaving the problem to multinational corporations, such as Weight Watchers. Fung fills this lacuna with his Hormonal Theory of Obesity. His evidence-based approach rests on 20 years of clinical work helping diabetics manage their illness and on engaging critically with scientific scholarship, namely, human studies published in peer-reviewed journals. While most health professionals focus on the symptoms of diabetes (abnormal blood glucose levels), The Obesity Code examines the causes of the disease, namely, excessive insulin secretion and insulin resistance.