Glucose is crucial to our survival. A constant supply of glucose circulates in our bloodstream, which, with the help of insulin, makes energy available. Glucose stores are also stored in the liver and muscles in the form of glycogen. We usually have about a day's supply of glucose in the form of glycogen. When blood glucose levels are low, the liver breaks down glycogen to raise blood glucose levels. When we need energy for muscle contraction and blood glucose levels are low, our muscles break down their glycogen stores.
How do we get energy without dietary carbohydrates?
When we eat, exercise, sit or sleep, our bodies are busy controlling and providing our energy supply. And, when needed, our bodies produce the energy they need from non-carbohydrate sources.
One of the ways our bodies do this is through gluconeogenesis, a process that uses non-carbohydrate substances to produce glucose. We can also use protein and fat for energy. For example, the amino acids in the proteins we consume can be used during gluconeogenesis to produce glucose. And triglycerides, the type of fat we store in adipose tissue, can be broken down through lipolysis and used to trigger a sequence of events that generate ketones when our glycogen stores run out.
In short, by relying less on carbohydrates for energy, you increase ketone production. Although the liver always produces some number of ketones for energy from fat, the more the body switches to fat as an energy source, the more ketones production increases. But eating too much protein can reduce ketone production, making it difficult to achieve and maintain ketosis, so a true ketogenic diet has restrictions on protein intake as well as carbohydrates.
How does the keto diet work?
The keto diet works because when you limit dietary carbohydrates – your body's main source of energy – your body breaks down stored fat and creates ketones, which are used for energy instead. However, calories still matter. If you overeat on protein and fats, and the total number of calories exceeds what your body burns, you still won't see weight loss. Foods high in fat and protein (the foundation of this diet) increase satiety, so usually your total calorie intake is lower than what your body burns, resulting in weight loss.