Keto Diet Glossary: A-Z Terms and Definitions

The Complete Keto Diet Glossary

The world of keto comes with its own vocabulary. This comprehensive glossary defines 80+ keto-related terms in plain, easy-to-understand language. Bookmark this page and refer back to it whenever you encounter an unfamiliar term.

A

Acetoacetate: One of the three ketone bodies produced by the liver during ketosis. It is measured in urine ketone tests and can be converted to beta-hydroxybutyrate or acetone.

Acetone: A ketone body that is produced as a byproduct of ketosis and exhaled through the breath. It is responsible for the characteristic “keto breath” that some people experience.

Autophagy: The body’s natural cellular cleanup process where damaged or dysfunctional cells are broken down and recycled. Both fasting and ketosis promote autophagy, which is associated with longevity and disease prevention.

Allulose: A rare sugar that tastes like regular sugar but has minimal impact on blood sugar and insulin. It contains about 0.4 calories per gram and is considered keto-friendly.

B

Beta-Hydroxybutyrate (BHB): The most abundant ketone body in the blood during ketosis. BHB is the primary fuel source for the brain and muscles when in a ketogenic state. Blood ketone meters measure BHB levels.

Bulletproof Coffee: A popular keto beverage made by blending black coffee with grass-fed butter and MCT oil. It provides sustained energy and helps increase fat intake.

Blood Ketone Meter: A device that measures beta-hydroxybutyrate levels in the blood via a finger prick. It is the most accurate method for measuring ketosis.

C

Carb Cycling: An eating strategy that alternates between high-carb and low-carb days. Some keto dieters use carb cycling to support intense exercise or break through plateaus.

Clean Keto: A version of the keto diet that emphasizes whole, unprocessed, nutrient-dense foods such as grass-fed meats, organic vegetables, and quality fats.

Cyclical Ketogenic Diet (CKD): A keto variation that includes periodic higher-carb “refeed” days, typically 5 keto days followed by 2 higher-carb days. Popular among athletes and bodybuilders.

Cortisol: A stress hormone produced by the adrenal glands. Chronically elevated cortisol can increase blood sugar, promote fat storage (especially belly fat), and impair ketosis.

D

Dirty Keto: A version of the keto diet that focuses solely on macronutrient ratios without regard for food quality. It may include processed foods, fast food, and artificial ingredients as long as carb limits are met.

E

Electrolytes: Minerals that carry an electrical charge and are essential for bodily functions including muscle contraction, nerve signaling, and hydration. The three key electrolytes on keto are sodium, potassium, and magnesium.

Erythritol: A sugar alcohol commonly used as a keto-friendly sweetener. It has zero net carbs, zero calories, and does not affect blood sugar or insulin levels.

Exogenous Ketones: Ketone supplements (usually BHB salts or esters) taken orally to raise blood ketone levels. They can provide energy and reduce keto flu symptoms but do not replace the need for dietary carb restriction.

F

Fat Adaptation (Fat-Adapted): The state in which your body has become highly efficient at burning fat and ketones for fuel. Full fat adaptation typically takes 2-6 weeks of consistent keto eating.

Fat Bombs: Small, high-fat keto snacks typically made from combinations of coconut oil, butter, cream cheese, nut butter, and cocoa. They help increase fat intake and satisfy cravings.

Fiber: A type of carbohydrate that the body cannot digest. Fiber does not raise blood sugar and is subtracted from total carbs to calculate net carbs.

G

Gluconeogenesis: A metabolic process in which the liver produces glucose from non-carbohydrate sources, primarily protein (amino acids) and glycerol. This process ensures that the small amount of glucose needed by certain cells is always available, even on a zero-carb diet.

Glycemic Index (GI): A measure of how quickly a food raises blood sugar levels. Low-GI foods cause a slower, smaller rise in blood sugar. Keto foods are generally very low on the glycemic index.

Glycogen: The stored form of glucose in the liver and muscles. When you start keto, glycogen stores are depleted within 24-48 hours, triggering the body to switch to fat burning.

H

HDL Cholesterol: High-density lipoprotein, often called “good” cholesterol. The keto diet typically increases HDL levels, which is associated with reduced cardiovascular risk.

Hyperketonemia: Elevated blood ketone levels. In the context of nutritional ketosis (0.5-3.0 mmol/L), this is normal and healthy. Extremely high levels (above 10 mmol/L) may indicate ketoacidosis, which is a medical emergency.

I

Insulin: A hormone produced by the pancreas that regulates blood sugar by signaling cells to absorb glucose. The keto diet lowers insulin levels, which promotes fat burning and improves insulin sensitivity.

Insulin Resistance: A condition in which cells become less responsive to insulin, requiring the pancreas to produce more insulin to maintain normal blood sugar. It is a precursor to type 2 diabetes and is improved by the keto diet.

Intermittent Fasting (IF): An eating pattern that cycles between periods of eating and fasting. Common protocols include 16:8 (16 hours fasting, 8 hours eating) and OMAD (one meal a day). IF pairs well with keto for enhanced fat loss.

K

Keto Adaptation: See Fat Adaptation.

Keto Breath: A fruity, metallic, or acetone-like taste or smell in the mouth caused by the ketone body acetone being exhaled. It is a sign of ketosis and typically diminishes over time.

Keto Flu: A collection of temporary symptoms (headache, fatigue, brain fog, nausea) experienced during the first 1-7 days of the keto diet, caused primarily by electrolyte depletion and dehydration.

Ketoacidosis: A dangerous medical condition (primarily affecting type 1 diabetics) in which blood ketone levels become extremely high (above 10 mmol/L) and blood becomes acidic. This is NOT the same as nutritional ketosis.

Ketogenesis: The metabolic process by which the liver produces ketone bodies from fatty acids. This process is activated when carbohydrate intake is very low.

Ketogenic Diet: A high-fat, moderate-protein, very-low-carbohydrate diet that induces ketosis. Standard macros are approximately 70-75% fat, 20-25% protein, 5-10% carbs.

Ketone Bodies: Molecules produced by the liver from fatty acids during periods of low carbohydrate intake. The three ketone bodies are beta-hydroxybutyrate (BHB), acetoacetate, and acetone.

Ketosis: A metabolic state in which the body uses ketone bodies (derived from fat) as its primary fuel source instead of glucose. Nutritional ketosis is typically indicated by blood ketone levels of 0.5-3.0 mmol/L.

L

Lazy Keto: A simplified version of the keto diet where only net carbs are tracked (kept under 20-50g per day) without tracking fat or protein intake.

LDL Cholesterol: Low-density lipoprotein, often called “bad” cholesterol. On keto, total LDL may increase, but LDL particle size often shifts from small dense (more dangerous) to large buoyant (less dangerous).

M

Macros (Macronutrients): The three main categories of nutrients that provide calories: fat, protein, and carbohydrates. On keto, the typical macro ratio is 70-75% fat, 20-25% protein, 5-10% carbs.

MCT Oil: Medium-chain triglyceride oil, typically derived from coconut oil. MCTs are rapidly absorbed and converted to ketones by the liver, making MCT oil a popular keto supplement for energy and focus.

Monk Fruit: A natural, zero-calorie sweetener derived from monk fruit (luo han guo). It is 150-200 times sweeter than sugar and does not affect blood sugar or insulin.

N

Net Carbs: The total carbohydrates in a food minus fiber and sugar alcohols. Net carbs represent the carbohydrates that affect blood sugar and ketosis. Formula: Net Carbs = Total Carbs – Fiber – Sugar Alcohols.

Nutritional Ketosis: The safe, controlled metabolic state achieved through dietary carbohydrate restriction, characterized by blood ketone levels of 0.5-3.0 mmol/L. Distinct from diabetic ketoacidosis.

O

OMAD (One Meal a Day): An extreme form of intermittent fasting where all daily calories are consumed in a single meal within a 1-hour eating window.

P

Plateau: A period during which weight loss stalls despite continued adherence to the keto diet. Plateaus are normal and can be broken through by adjusting macros, adding exercise, trying intermittent fasting, or managing stress.

S

Standard Ketogenic Diet (SKD): The most common form of the keto diet with macros of approximately 70-75% fat, 20-25% protein, and 5-10% carbohydrates.

Stevia: A natural, zero-calorie sweetener derived from the stevia plant. It is 200-300 times sweeter than sugar and is one of the most popular keto-friendly sweeteners.

Sugar Alcohols: A category of sweeteners (erythritol, xylitol, maltitol, sorbitol) that are partially absorbed by the body. Erythritol has the least impact on blood sugar and is the most keto-friendly sugar alcohol.

T

Targeted Ketogenic Diet (TKD): A keto variation that allows 25-50g of additional carbs around workouts to support high-intensity exercise performance.

Triglycerides: A type of fat found in the blood. High triglyceride levels are a risk factor for heart disease. The keto diet typically reduces triglyceride levels significantly.

Z

Zero-Carb: An extreme dietary approach that eliminates all carbohydrates, typically consisting only of animal products (meat, fish, eggs, butter). Also known as the carnivore diet.

Keep Learning

Understanding the language of keto empowers you to make informed decisions about your diet and health. Refer back to this glossary whenever you encounter an unfamiliar term, and explore our other guides for deeper dives into specific topics.