Basic Last updated 12 July 2026 · 6 min read

What is the ketogenic diet?

The ketogenic diet is a high-fat, low-carbohydrate eating plan that shifts your body into ketosis — a metabolic state where fat, rather than glucose, becomes your primary fuel source. In practice, it means keeping total carbohydrate intake low enough (usually under 30–50 grams per day) that the liver begins producing ketone bodies from fat.

For beginners, success on keto means focusing on whole foods — meat, fish, eggs, dairy, non-starchy vegetables, nuts — and limiting grains, sugars, starches and most fruit. The target proportions are approximately 70–75% of calories from fat, 20–25% from protein, and 5–10% from carbohydrates.

Note Ketogenic is not a single diet. Variants include the standard ketogenic diet (SKD), targeted ketogenic diet (TKD) for athletes, and the therapeutic ketogenic diet used clinically for refractory epilepsy since the 1920s.

The three macronutrient targets

A standard ketogenic day, expressed as a percentage of total calories:

Fat 70–75% Protein 20–25% Carbs 5–10%
Macronutrient% of caloriesGrams on a 2 000 kcal dayRole
Fat70–75%155–167 gPrimary fuel source in ketosis.
Protein20–25%100–125 gPreserves lean mass; adequate, not high.
Carbohydrate5–10%25–50 gKept low enough to sustain ketosis.

What ketosis actually means

When dietary carbohydrates fall below roughly 50 g per day for several days, liver glycogen stores deplete. The liver then begins converting fatty acids into three ketone bodies — beta-hydroxybutyrate (BHB), acetoacetate, and acetone — which most tissues, including the brain, can use for energy.

Nutritional ketosis is conventionally defined as blood BHB concentrations between 0.5 and 3.0 mmol/L. This is distinct from diabetic ketoacidosis, a pathological state that occurs when insulin is absent — at ketone levels ten to twenty times higher.

Key takeaway Ketosis is a normal metabolic state. Humans enter mild ketosis every night during sleep. The ketogenic diet simply extends and deepens it.
Evidence review Last updated 12 July 2026 · 9 min read

Benefits and risks, with the evidence labelled

The ketogenic diet is well-studied in some contexts (epilepsy, short-term weight loss, type 2 diabetes) and under-studied in others (long-term cardiovascular outcomes, athletic performance). We cite a medical or academic source for the claims we make.

✓ Likely benefits

  • Weight lossMeta-analyses show faster short-term loss vs. low-fat diets, largely through appetite reduction. Evidence: strong.
  • Blood-sugar controlLower HbA1c and reduced medication in type 2 diabetes (Virta trial, 2-year data). Evidence: strong.
  • Reduced hungerConsistently reported across trials; likely mediated by higher satiety from fat and protein. Evidence: moderate.
  • Therapeutic use in epilepsyA first-line treatment for drug-resistant childhood epilepsy since the 1920s. Evidence: strong (clinical).
  • Improved triglycerides / HDLLower triglycerides and higher HDL commonly reported. LDL response is individual. Evidence: moderate.

! Potential risks

  • Keto flu (first 1–2 weeks)Headache, fatigue, irritability from electrolyte loss. Managed with salt, magnesium, potassium. Common, short-term.
  • Raised LDL cholesterolA subset of lean individuals show large LDL increases. Monitor with lipid panel and ApoB. Variable.
  • Nutrient gapsFibre, potassium, magnesium and folate intake can fall if non-starchy vegetables are neglected. Avoidable.
  • Kidney stonesSmall increased risk in clinical-ketogenic protocols, particularly in children. Adequate hydration reduces risk. Uncommon.
  • ContraindicationsPregnancy, type 1 diabetes, pancreatitis, certain genetic disorders. Always consult a clinician. Specific populations.
Practical A sample from 8169 foods · use search to look up any food

Foods to eat, and foods to avoid

The working principle is simple: prefer whole foods that occur in nature without a label, limit processed carbohydrates, and keep total carb intake within your target.

✓ Eat regularly

Elk, free range, roast, eye of round, raw (Shoshone Bannock) CRACKER BARREL, grilled sirloin steak Buffalo, free range, top round steak, cooked (Shoshone Bannock) Fish, salmon, king, with skin, kippered, (Alaska Native) Buffalo, free range, top round steak, raw (Shoshone Bannock) Smelt, dried (Alaska Native) Fish, salmon, red, canned, bones removed (Alaska Native) Seal, bearded (Oogruk), meat, partially dried (Alaska Native) Oil, whale, bowhead (Alaska Native) Fish, salmon, coho (silver), raw (Alaska Native) Oil, spotted seal (Alaska Native) Fish, sheefish, raw (Alaska Native) Fish, salmon, red, (sockeye), canned, smoked (Alaska Native) Deer (venison), sitka, raw (Alaska Native) Walrus, meat, dried (Alaska Native) Moose, meat, raw (Alaska Native) Fish, salmon, red, (sockeye), kippered (Alaska Native) Squirrel, ground, meat (Alaska Native) Fish, salmon, king, chinook, smoked, brined (Alaska Native) Oil, bearded seal (Oogruk) (Alaska Native) Seal, bearded (Oogruk), meat, raw (Alaska Native) Sea cucumber, yane (Alaska Native) Duck, scoter, white-winged, meat (Alaska Native) Whale, bowhead, subcutaneous fat (blubber) (Alaska Native) Oopah (tunicate), whole animal (Alaska Native) Caribou, rump meat, half dried (Alaska Native) Whale, bowhead, skin and subcutaneous fat (muktuk) (Alaska Native) Owl, horned, flesh, raw (Alaska Native) Fish, salmon, king, chinook, smoked and canned (Alaska Native) Pectin, liquid

✗ Limit or avoid

Sweetener, herbal extract powder from Stevia leaf Sweeteners, tabletop, fructose, dry, powder Sugars, granulated Sugar, turbinado Sugars, powdered Sugars, granulated Sugars, granulated Sweeteners, for baking, contains sugar and sucralose Strawberry-flavor beverage mix, powder Desserts, rennin, vanilla, dry mix Candies, gumdrops, starch jelly pieces Candies, hard, dietetic or low calorie (sorbitol) Beverages, tea, instant, decaffeinated, lemon, sweetened Beverages, orange-flavor drink, breakfast type, powder Sugars, brown Candies, hard Beverages, lemonade-flavor drink, powder Beverages, tea, instant, lemon, sweetened, powder Beverages, tea, instant, lemon, with added ascorbic acid Beverages, Whiskey sour mix, powder Beverages, Lemonade, powder Sweeteners, for baking, brown, contains sugar and sucralose Puddings, lemon, dry mix, instant Frostings, white, fluffy, dry mix Beverages, tea, green, instant, decaffeinated, lemon, unsweetened, fortified with vitamin C Chewing gum Beverages, drink mix, QUAKER OATS, GATORADE, orange flavor, powder Puddings, tapioca, dry mix, with no added salt Puddings, tapioca, dry mix Frostings, vanilla, creamy, dry mix

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Practical rule Stay at or below 30 g of net carbs per day (total carbs minus fibre). Most non-starchy vegetables cost fewer than 5 g net carbs per generous portion.