Here are a few terms that you will see referenced often among metabolic freedom users worldwide. It’s good to familiarize yourself with them before you start your journey.
Autophagy (aw-TAH-fuh-jee): A process by which a cell breaks down and destroys old, damaged, or abnormal proteins and other substances in its cytoplasm (the fluid inside a cell). The broken-down products are then recycled for important cell functions, especially during periods of fasting. This can occur after 16 to 18 hours of fasting but can happen sooner or later depending on your metabolic health.
Basal metabolic rate (BMR): The rate at which the body uses energy while at rest to keep vital functions going, such as breathing and keeping warm. In short, this is the number of calories your body would burn if you sat on the couch all day. Overweight people who have calorically restricted typically have lower basal metabolic rates.
Blood sugar: The blood glucose level is the amount of glucose in the blood. Glucose is a sugar that comes from the foods we eat, and it’s also formed and stored inside the body via liver and muscle cells. Healthy blood sugar should be between 70 and 90 mg/dL (milligrams per deciliter) when in a fasted state.
Breaking a fast: The term breakfast simply means you are “breaking your fast” from not eating food overnight. We also use this term to refer to a food or drink that raises blood sugar and starts the digestive system, thus turning off the healing benefits of being in a fasted state. In short, this means you have pulled yourself out of a fast and into a fed state.
Eating window: The period throughout your day when you are eating. You would eat all your meals and snacks within a particular window of time each day. This timeframe can vary according to the person’s preference and the plan they choose to follow.
Fasting window: The period throughout your day when you are not eating or drinking beverages that raise glucose. Any food or drink that raises blood sugar and starts the digestive process will pull you out of your fasted window.
Fat-adapted: Fat adaptation can occur to different degrees and across a spectrum dependent on the degree of carb restriction. This usually occurs generally when carbohydrates are restricted to under 50 total grams per day, over a period of seven days. You are fat-adapted when you have shifted away from primarily burning sugar (glucose) to burning fat (ketones).
Insulin: A hormone made by the islet cells of the pancreas. Insulin controls the amount of sugar in the blood by moving it into the cells, where it can be used by the body for energy. Insulin is the primary fat-storage hormone.
Insulin resistance: Insulin resistance is when cells in your muscles, fat, and liver don’t respond well to insulin and can’t easily take up glucose from your blood. As a result, your pancreas makes more insulin to help glucose enter your cells. A more accurate term would be hyperinsulinemia. If not corrected, over time this can lead to prediabetes, and eventually diabetes.
Intermittent fasting (IF): Going without food for 12 to 20 hours.
Keto-adapted: Keto adaptation represents a more comprehensive reshaping of many physiologic systems. Keto adaptation only happens when carbs are restricted to a point that induces sustained nutritional ketosis. This process takes longer than fat adaptation. It is estimated to take 6 to 12 weeks.
Keto flexing: Going in and out of ketosis after you’ve taught your body to be a fat burner. We also call this Metabolic Flexing. Some people call this carbohydrate cycling or keto cycling.
Ketones: A by-product of fat metabolism, ketones are the signal that your liver is now burning energy from fat, not sugar. The liver creates three different types of ketones: acetone, measured in the breath; acetoacetate, measured in the urine; and beta hydroxybutyrate (BHB), measured in the blood. I suggest testing blood ketone measurements for BHB; the optimal range is 0.5–3.0 mmol/L (millimoles per liter).
Ketosis: A metabolic process that occurs when your body doesn’t have enough carbohydrates to burn for energy. When you restrict carbohydrates in your diet, you lower the hormone insulin, which allows for fat-burning. You can enter ketosis the preferred way, endogenously (from within) by burning fat for fuel, or exogenously (from outside) from exogenous ketones.
Metabolic flexibility: Being metabolically flexible enough to switch between burning sugar (glucose) and burning fat (ketones) without any problems.
Mitochondria: Mitochondria are membrane-bound cell organelles (mitochondrion, singular) that generate most of the chemical energy needed to power the cell’s biochemical reactions. Chemical energy produced by the mitochondria is stored in a small molecule called adenosine triphosphate (ATP). Mitochondria contain their own small chromosomes. Mitochondria are also called the powerhouse of the cell.
mTOR: This stands for “mechanistic target of rapamycin.” A cellular signaling pathway that gets triggered when amino acids and insulin levels within the cell increase, which usually happens in the fed state. It stimulates anabolic growth and runs counter to autophagy, which is more catabolic in repair. Once stimulated, the mTOR pathway will promote cellular growth.
Stored sugar: The amount of glucose that is stored in tissues like the liver, fat, brain, muscle, and eyes.
Sugar burner: An energy system that burns fuel from the foods you eat. This energy system runs on the glucose created from food, primarily from carbohydrates.
Water fasting: A fast that involves drinking only water. This means a period (usually more than 16 hours) without food, only water.