The Obesity Code: Unlocking the Secrets of Weight Loss

Carbohydrates are one of three macronutrients alongside proteins and fats. Carbs are composed of sugars and function as the body’s prime source of energy. Several popular diets, such as the Atkins diet and Paleo recommend avoiding carbs. Fung refines this approach, advising readers to reduce their consumption of processed carbs because they are quickly absorbed and cause insulin spikes.

Often called the stress hormone, cortisol is produced in the adrenal cortex and mediates the fight-or-flight response by enhancing the availability of glucose. High cortisol levels raise glucose and insulin, thereby driving weight gain while low cortisol levels result in weight loss. Stress management and adequate sleep are key to controlling cortisol.

Diabesity is a compound word combining diabetes and obesity. Fung uses the term to describe the well-established link between type 2 diabetes and obesity. The diseases share a root cause, namely, high, persistent insulin levels.

Ghrelin is a hunger-regulating hormone produced and released primarily by the stomach. Caloric reduction stimulates ghrelin, which makes dieters hungry and renders low-calorie diets counterproductive.

Gluconeogenesis (or the “making of new sugar”) is a process that transforms fats into glucose, resulting in weight loss. Gluconeogenesis occurs during long periods of fasting, usually at night.

Glycogen is a form of energy created from glucose in the liver. The body can easily convert glucose to glycogen and back again, depending on food intake and energy needs.

Homeostasis describes the body’s ability to adapt to change and return to its original state. When a person loses weight, the body compensates to raise its set point, largely with hormonal responses.

Hormones are chemical messengers that regulate many body systems and processes, such as blood sugar levels, appetite, and fat storage. Fung argues that obesity is a hormonal disease, not a caloric disorder.

Incretins are metabolic hormones that augment the secretion of insulin in the stomach in response to carbohydrates, proteins, and fats. Since all foods, and not just carbohydrates, stimulate insulin, all foods can cause weight gain.

Insulin is a hormone that regulates the metabolism of carbohydrates, proteins, and fats by promoting the absorption of blood glucose into the liver and other tissues. Fung describes insulin as a storage hormone: Insulin levels rise after eating, leading the body to store sugar and fat. When there is no intake of food, insulin levels fall, prompting the body to burn of sugar and fat. According to Fung, obesity results from high, persistent insulin levels.

Ketosis occurs when the body burns fat instead of glucose for energy. Avoiding carbohydrates is the fastest way to trigger ketosis since the body no longer has a ready supply of glucose to burn. Fung recommends intermittent fasting to allow the body to regularly enter this metabolic state.

Leptin is a satiety hormone that aids in maintaining a normal body weight. Obese people tend to have high levels of leptin and leptin resistance, which causes them to not have signals from the body when they have eaten enough food.

De novo lipogenesis (or “to make new fat”) is the conversion of carbohydrates to fat. After the liver reaches its saturation point of glycogen, the body triggers de novo lipogenesis and begins storing glucose as fat.