What keto actually is.

Keto means zero carbs, forever.

It means low carbs, not no carbs. Most people stay between 20 and 50 grams of net carbs per day — enough room for non-starchy vegetables, berries, nuts, and a little dairy. And it doesn't have to be permanent. Many people use a stricter phase to lose weight or improve metabolic markers, then settle into a sustainable low-carb pattern of eating that they can hold for life.

Ketosis is the same as ketoacidosis.

They share a word and almost nothing else. Nutritional ketosis produces blood ketone levels of roughly 0.5–3 mmol/L — a normal, regulated metabolic state. Diabetic ketoacidosis is a medical emergency seen mainly in type 1 diabetes, with ketone levels often above 15 mmol/L combined with very high blood sugar and a dangerously acidic blood pH. A healthy pancreas makes the second one essentially impossible.

All that fat will clog your arteries.

Decades of randomized trials comparing low-carb to low-fat diets have not shown the heart-attack risk that the simple "fat clogs arteries" model predicts. In most studies, well-formulated keto diets lower triglycerides, raise HDL, and shrink the small dense LDL particles most associated with cardiovascular risk. Total LDL can rise in some people; that's a conversation worth having with a clinician who looks at the full lipid panel, not just one number.

You have to hit exact macros every day.

You don't. The one number that actually matters is keeping carbohydrate low enough to stay in ketosis — usually under about 20–30 grams of net carbs. Protein adapts to your body weight and activity, and fat is mostly a lever for satiety: eat enough to feel full, less when you want to lose weight. Tracking apps are useful in the first few weeks to learn what foods contain. After that, most people stop measuring.

You'll lose all your muscle.

Muscle loss happens when you eat too little protein or stop using your muscles, not because of ketosis itself. Studies of resistance-trained athletes on ketogenic diets show preserved — and sometimes increased — lean mass when protein intake is adequate (roughly 1.2–2.0 g per kg of body weight) and training continues. The fuel changes; the building blocks don't.

Your brain needs glucose to function.

The brain has an absolute requirement for some glucose, but the liver makes it on demand from protein and the glycerol backbone of fat — a process called gluconeogenesis. The rest of the brain's energy needs are met by ketones, which cross the blood-brain barrier and are used directly by neurons. Many people report sharper focus once adapted, which is consistent with the brain running on a steadier fuel supply instead of a roller-coaster of glucose spikes.