On a regular diet, our bodies break down carbohydrates into glucose to use for fuel.
Carbs are broken down into glucose and transported through the bloodstream attached to insulin, a hormone.
Insulin takes glucose into the cells of our muscles and liver and stores it there for later use.
Leftover glucose stays in our blood (why diabetics have high blood sugar --it can't get in to tissues).
In a ketogenic diet, our bodies learn to use fat as fuel in the form of ketones. Your liver breaks down fat into ketones to use for energy, and stores only what extra fat is needed.
When you've made the switch to eating high-fat and your body has adapted, it's called being in ketosis, or a ketotic state
Ketones are excreted through urine, so you can test your ketone levels by testing your urine (almost like a pregnancy test)
LOW-CARB MACRO BREAKDOWN
Maintaining ketosis involves more than just fat; protein is an important part of the ketogenic, low-carb diet (1).
Make sure you are getting the right amount of protein to maintain muscle (looking to build muscle? You may need more protein!).
But be careful, protein can also be broken down into glucose and used for energy in some cases, but we want to make sure our fat is fuel, not protein!
Eating too much protein may stop you from truly using fat as fuel (a process called glycogenesis, where protein is broken down and changed into glucose) and keep you out of ketosis and you won't be able to reap the benefits of the ketogenic diet (2)!
LOW-CARB, KETO MATH
Let's figure out how much protein you need per day:
Most healthy people seeking to maintain muscle mass need only 0.8-1.0 grams of protein per kilogram of body weight. If you are looking to gain muscle, you may need to add more protein, but try this first:
Convert your body weight to kilograms: 1 kg = 2.2 lbs, so divide your weight by 2.2
Eg: 145 lbs/2.2 = 65.9 kg
Then, multiply 0.8 x your weight in kg
Eg: 65.9 x 0.8 = 52.7 gm = 53 gm protein minimum
To get your maximum, multiple 1.0 x your weight in kg
Eg: 65.9 x 1.0 = 65.9 gm = 66 gm protein maximum
In this example, someone weighing 145 pounds would need to eat somewhere between 53 gm and 66 gm of protein per day to maintain their muscle mass on a ketogenic diet. This amount may change as you experiment with your diet, you may need less protein to maintain ketosis.
What about fat and carbs? Now that you understand how to calculate your protein needs, try using the niKETO macronutrient calculator to find out how many grams of fat and carbs to eat on your ketogenic diet!
(1) Paddon-Jones, D., Westman, E., Mattes, R. D., Wolfe, R. R., Astrup, A., & Westerterp-Plantenga, M. (2008). Protein, weight management, and satiety. The American Journal of Clinical Nutrition, 87(5), 1558S–1561S. https://doi.org/10.1093/ajcn/87.5.1558S.
(2) Veldhorst, M. A. B., Westerterp-Plantenga, M. S., & Westerterp, K. R. (2009). Gluconeogenesis and energy expenditure after a high-protein, carbohydrate-free diet. The American Journal of Clinical Nutrition, 90(3), 519–526. https://doi.org/10.3945/ajcn.2009.27834.