On the ketogenic diet, carbohydrates are restricted and so cannot provide for all the metabolic needs of the body. Instead, fatty acids are used as the major source of fuel. These are used through fatty-acid oxidation in the cell's mitochondria (the energy-producing parts of the cell). Humans can convert some amino acids into glucose by a process called gluconeogenesis, but cannot do this by using fatty acids.[56] Since amino acids are needed to make proteins, which are essential for growth and repair of body tissues, these cannot be used only to produce glucose. This could pose a problem for the brain, since it is normally fuelled solely by glucose, and most fatty acids do not cross the blood–brain barrier. However, the liver can use long-chain fatty acids to synthesise the three ketone bodies β-hydroxybutyrate, acetoacetate and acetone. These ketone bodies enter the brain and partially substitute for blood glucose as a source of energy.[55]
Blood specimens were obtained at weeks 0, 8, and 16 after the participant had fasted overnight. The following serum tests were performed in the hospital laboratory using standardized methods: complete blood count, chemistry panel, lipid panel, thyroid-stimulating hormone, and uric acid. A non-fasting specimen was also drawn at weeks 4 and 12 to monitor electrolytes and kidney function.

The main advantage of the low-carb diet is that it causes you to want to eat less. Even without counting calories most overweight people eat far fewer calories on low carb. Sugar and starch may increase your hunger, while avoiding them may decrease your appetite to an adequate level. If your body wants to have an appropriate number of calories you don’t need to bother counting them. Thus: Calories count, but you don’t need to count them.

Sleep enough – for most people at least seven hours per night on average – and keep stress under control. Sleep deprivation and stress hormones raise blood sugar levels, slowing ketosis and weight loss a bit. Plus they might make it harder to stick to a keto diet, and resist temptations. So while handling sleep and stress will not get you into ketosis on it’s own, it’s still worth thinking about.