Keto FAQ

The ketogenic (keto) diet is a very low-carbohydrate, high-fat diet. When carbohydrate intake drops low enough (for most adults, somewhere between 20 and 50 g of net carbs a day), liver glycogen runs down and the liver turns more fatty acids into ketone bodies (beta-hydroxybutyrate, acetoacetate, and acetone), which the body uses for fuel. This state is called nutritional ketosis, usually defined as blood beta-hydroxybutyrate of 0.5 to 3.0 mmol/L.

Most adults stay in nutritional ketosis at 20 to 50 g of net carbs a day. Starting at about 20 to 25 g gives a margin that works for most people; our calculators use 25 g for standard keto and 20 g for lazy keto. Very active people often stay in ketosis at higher intakes. Net carbs are total carbs minus fiber, minus sugar alcohols depending on the type: our Net Carb Calculator subtracts erythritol fully and other sugar alcohols at 50%.

Most people reach nutritional ketosis within about 2 to 7 days of keeping net carbs low, faster toward 20 g a day. The timeline depends on your glycogen stores, activity level, and what you ate before. A blood ketone reading of 0.5 mmol/L or above confirms it; urine strips and breath meters are less precise. Above about 50 g of net carbs a day, most people do not reach ketosis at all.

Net carbs estimate the carbohydrate your body digests into blood sugar. The formula is: Net Carbs = Total Carbs minus Fiber minus Sugar Alcohols, adjusted by type. Fiber passes through the small intestine largely undigested and does not raise blood glucose much. Erythritol has very little effect on blood glucose and is subtracted fully; other sugar alcohols, including maltitol, are partly absorbed, so our Net Carb Calculator subtracts them at 50%.

They overlap but are not the same. Atkins is a phased low-carb plan that starts very low (and is ketogenic in its first phase) and gradually adds carbohydrate back. Keto aims to stay in ketosis for as long as you follow it, so carbohydrate stays low throughout and most calories come from fat. Both can produce ketosis early on.

Not necessarily at first. Many people find their appetite falls on keto and they lose weight without tracking calories. If weight loss stalls, calories matter: fat is calorie-dense (9 kcal per gram, against 4 for carbs and protein) and easy to overeat. Our Keto Macro Calculator gives a calorie target you can use as a guide.

A typical keto day lands around 65 to 75% of calories from fat, 20 to 30% from protein, and about 5 to 10% from net carbs. Those percentages are a result, not a starting point. Our calculators set net carbs in grams (25 g for standard keto), set protein at about 0.8 g per pound of lean body mass (a practical range is 0.7 to 1.0 g), and fill the remaining calories with fat. Setting protein in grams keeps it steady when you cut calories.

More than many people fear. The idea that extra protein turns into glucose and stops ketosis is overstated: the body makes glucose from protein according to need, not simply according to how much protein you eat. A practical range is 0.7 to 1.0 g per pound of lean body mass, or 0.6 to 1.0 g per pound of goal weight if you do not know your body fat. Too little protein is the more common problem. If you have kidney disease, set protein with your doctor.

Many keto calculators apply a fixed percentage split, such as 70% fat, 25% protein, and 5% carbs, to your calories. Ours sets protein from your lean body mass (from your body fat percentage, or the Boer formula if you do not know it), sets net carbs in grams, and lets fat fill the rest. Calories come from the Mifflin-St Jeor equation, or Katch-McArdle if you enter body fat, with activity multipliers, a goal adjustment, and minimum calorie floors. The formulas are published on our methodology page. All of these are estimates, so adjust from your real results.

Fat is the main energy source on keto, but energy balance still applies. Eating more fat than you need for energy creates a calorie surplus, and that surplus is stored. If weight loss is your goal and you are eating above your calorie target, a stall or gain is possible on keto too. High fat is part of keto; unlimited fat is not.

Your daily calorie and macro targets do not change with meal timing; only how you spread them across your eating window does. Our IF + Keto Calculator gives your targets and splits them across your chosen window (14:10, 16:8, 18:6, 20:4, OMAD, or 5:2). For 5:2, it sets the normal days so your weekly average matches your goal. Making the first meal protein-forward helps you reach your protein target in a shorter window.

Keto flu is a set of symptoms (headache, tiredness, brain fog, cramps, nausea, irritability) that often appears in the first few days of cutting carbohydrate. A big part of it is sodium and fluid loss: as insulin falls, the kidneys excrete more sodium, and potassium losses can rise too. Getting enough electrolytes helps most people: total sodium of about 3,000 to 5,000 mg a day (salt your food, drink broth), potassium-rich foods such as avocado and leafy greens, and enough magnesium. If you have high blood pressure, heart failure, or kidney disease, or take diuretics, ACE inhibitors, or ARBs, set these with your clinician.

As total daily intake from food, broth, salt, and any supplement combined: sodium about 3,000 to 5,000 mg; potassium about 3,000 to 4,700 mg, mostly from food and never below the NIH Adequate Intake (2,600 mg for women, 3,400 mg for men); magnesium about 300 to 500 mg, with supplemental magnesium at or below 350 mg a day, the NIH upper limit. Needs are higher if you exercise hard or sweat a lot. Do not take potassium supplements or salt substitutes without medical advice if you have kidney disease or take ACE inhibitors, ARBs, or potassium-sparing diuretics. Our Electrolyte Calculator personalizes these targets.

For most healthy people it is uncomfortable rather than dangerous, and it usually eases within a week or two, faster with enough sodium and fluid. If you take blood pressure medication or diuretics, talk to your doctor before starting keto, because fluid and electrolyte shifts can interact with them. Seek care for chest pain, fainting, a racing or irregular heartbeat, or vomiting you cannot keep fluids down through.

In people with healthy kidneys and liver, studies of ketogenic diets have not shown organ damage, though long-term data are limited. Kidney stones are a known risk in some people, particularly on long-term medical ketogenic diets, so staying well hydrated matters. If you already have kidney or liver disease, keto needs medical supervision, including how much protein to eat. Either way, tell your doctor about your diet.

Not on your own, but take it seriously. Cholesterol response to keto varies a lot: triglycerides usually fall and HDL usually rises, but LDL often goes up, and in some lean, active people it rises sharply. Whether LDL raised this way carries the same heart risk as LDL raised on a typical diet is not settled. Get a full lipid panel before and a few months after starting, and review the change with your doctor, who can weigh it against your family history and other risk factors; an ApoB test can add useful context. An LDL of 190 mg/dL or more needs a clinical look whatever your diet. Our Metabolic Health Calculator compares before-and-after labs side by side.

The core numbers work the same way. Our calculators set protein from lean body mass for everyone (about 0.8 g per pound of lean mass), with no separate female percentage; sex already enters the calorie estimate through the Mifflin-St Jeor equation. What differs is context: water retention and appetite shift across the menstrual cycle, thyroid conditions are more common in women, and very large calorie deficits can disrupt periods. Our Women's Keto Calculator adds notes for the cycle, perimenopause, and menopause.

It can. In women with PCOS, lower insulin and weight loss may help cycles become more regular, based on small studies. On the other hand, eating too little energy on any diet can suppress the hypothalamic-pituitary-ovarian (HPO) axis and cause irregular or missed periods. Eating enough is the main safeguard. If your cycle changes and does not settle within a couple of months, see your doctor.

For most healthy women it can be, and some find it helps with weight and blood sugar, though there are few trials specific to menopause. Our calculator does not apply a separate menopause calorie cut; it estimates your needs from your age, size, and activity, and progress over a few weeks is the best guide to adjusting. Protein and resistance training matter more after menopause for keeping muscle. Talk to your doctor if you take HRT or blood pressure medication.

It may help some women. PCOS is often linked to insulin resistance, and cutting carbohydrate lowers insulin. A small 2005 pilot study reported weight loss and lower fasting insulin, free testosterone, and LH/FSH ratio over 24 weeks, but only five women finished it, so larger trials are needed. Our PCOS Keto Calculator sets 20 g of net carbs a day if you have insulin resistance and 25 g if you do not or are unsure, with protein set from lean body mass. Work with your doctor, especially if you take metformin or other PCOS medications.

Standard Keto (SKD): low net carbs (25 g in our calculator), protein from lean mass, fat for the rest. Lazy Keto: track only net carbs (20 g a day or less). Dirty Keto: the same targets as standard keto from any food, processed included. Targeted Keto (TKD): standard keto plus 15 to 30 g of fast carbs about 30 minutes before training. Cyclical Keto (CKD): 5 to 6 keto days and 1 to 2 carb-up days a week. Carnivore: animal foods only, close to zero carbs. See our Keto Types Guide for a comparison table.

For many beginners, yes. Staying at or under about 20 g of net carbs a day produces ketosis for most people, and many find their appetite drops enough to lose weight without tracking anything else. The risks are eating more calories than you need from calorie-dense foods, and eating too little protein. Lazy keto is a simple start; full tracking helps if you stall or have specific goals.

Usually, in effect. With almost no carbohydrate, most people on carnivore are in ketosis, though protein is higher than on standard keto: our Carnivore Calculator sets protein at 2.2 g per kg of lean body mass (about 1.0 g per pound of lean mass) and lets fat fill the rest. The main differences from standard keto are no plant foods (so no fiber) and more reliance on organ meats for some micronutrients. Some people try it for autoimmune or gut conditions, but that evidence is very early: surveys and case reports, not trials.

Cyclical keto is for people who train hard and want carbohydrate for performance, while eating keto most of the week. A typical week is 5 to 6 keto days and 1 to 2 carb-up days. It suits athletes with high glycogen demands (CrossFit, HIIT, team sports) more than people who train lightly, and it is easier to run once you know how standard keto works for you. Our Cyclical Keto Calculator gives both keto day and carb-up day targets; on carb-up days protein stays the same, fat drops to about 20% of calories, and carbs fill the rest.

The first week or two often bring a quick drop of about 3 to 7 lb, mostly water released as glycogen stores fall, not fat. After that, fat loss on keto is similar to other diets at the same calorie intake: roughly 0.5 to 2 lb a week depending on your deficit and starting weight, slowing as you get lighter. Our Weight Loss Calculator gives a week-by-week projection that recalculates your calorie burn as your weight falls.

Stalls are common, and there is no fixed week when they happen. The usual causes: eating more than you realize (especially calorie-dense fats, nuts, and cheese), hidden carbs in sauces or packaged foods, water retention hiding fat loss, poor sleep, or a smaller deficit than before because a lighter body burns less. Recalculate your calories at your current weight, track carefully for a week, and check that net carbs are where you think. A modest calorie reduction or more daily movement are the usual next steps.

Any diet with a calorie deficit can cost some muscle, and keto is no exception if protein is too low. The protections are the same on any diet: enough protein (at least about 0.7 g per pound of lean body mass), regular resistance training, and a deficit that is not excessively large. With those in place, studies generally show keto preserves muscle about as well as other diets; it does not have a clear advantage.

Yes. Resistance training helps preserve muscle during weight loss, and regular activity improves insulin sensitivity and uses up glycogen, which can help early in keto. High-intensity exercise often feels harder for the first few weeks; many people find performance returns after several weeks of adaptation, though some high-intensity performance may stay lower without carbohydrate, which is why some athletes use targeted or cyclical keto.