Keto made easy

Chapter 1: What a Ketogenic Diet Is and How Ketosis Works

A ketogenic diet is any way of eating, kept up over time, that holds your blood ketones in the nutritional-ketosis range; you get there by eating few enough carbohydrates that your liver starts turning fat into ketones.

On this page

The short answer

Your body normally runs mostly on glucose from carbohydrates. When you cut carbs far enough, for long enough, your liver starts making ketone bodies from fat. Your brain and muscles can use those ketones as fuel. That state is called ketosis.

A ketogenic diet is simply a diet that keeps you there. It is not a list of approved brands or a set of banned foods. It is a carb limit that is low enough, for you, to keep ketone production switched on.

KetoDick on this: he defines a ketogenic diet the same way, by its outcome. In his telling, any habitual mix of foods that keeps blood ketones in the nutritional-ketosis range counts as ketogenic (video ffwBPoKxlDI; video s_sNd1v8Low).

How ketosis happens, step by step

The steps below follow the order the liver works through. The biochemistry is summarized in the NIH StatPearls chapter on ketogenesis (Dhillon & Gupta).

  1. Carbs go down. You eat few digestible carbohydrates, so less glucose enters your blood from food.
  2. Glycogen drains. Your liver and muscles store glucose as glycogen. With little new glucose coming in, the body uses up those stores over the first days.
  3. Insulin falls. Insulin is the hormone that moves glucose into cells and tells the body to store fuel. With less glucose, less insulin is released.
  4. Stored fat is broken down. Lower insulin lets fat cells release fatty acids into the blood.
  5. The liver makes ketones. Inside the liver's mitochondria, fatty acids are turned into three ketone bodies: acetoacetate, beta-hydroxybutyrate (BHB) and acetone. StatPearls notes the process is regulated by insulin and glucagon (Dhillon & Gupta).
  6. The body uses ketones as fuel. Muscles and the brain take up ketones and burn them for energy.

The brain's ability to run on ketones is well documented. In a 1967 study of people fasting for weeks, BHB and acetoacetate replaced glucose as the brain's main fuel (Owen et al. 1967).

KetoDick on this: the mechanism he gives in nearly every explainer is the same chain: restrict carbs, glucose and glycogen run down, insulin falls, the fat-breaking enzyme he calls lipase can work, and ketones are made (video s_sNd1v8Low).

For the detail on each ketone body, see What Ketosis Is.

Keto is defined by the result, not a food list

Because keto is defined by ketones in the blood, no single food is "keto" or "not keto." What matters is the total carb dose across the day and the week.

This has two practical effects:

KetoDick on this: he says there are "no banned foods," only doses, and that some foods are keto only "at an eyedropper's worth" (from the video; video UygKGoP_BtA). He also points out that a diet of one grain of rice a day would be ketogenic, which is why he says some ketogenic diets are "dumb" (video 1JbK1_ClDmY).

For foods grouped by how much carb they carry, see What Can I Eat on Keto?.

Low carb vs keto

Keto is one kind of low-carb diet. The difference is how low.

Low carb Keto
Goal Fewer carbs than a typical diet Few enough carbs to raise blood ketones
Carb limit Varies widely by plan Low enough that the liver keeps making ketones
Ketones raised? Not necessarily Yes, by definition
Main fuel Mixed glucose and fat Mostly fat and ketones

How low is low enough differs from person to person. That is why you will see different carb numbers in different places. The Carbs chapter and How Many Carbs cover this in depth.

KetoDick on this: his working number has changed over the years. His 2017 explainers give under 20 g of carbs as the starting point, with some people tolerating up to 50 g (video s_sNd1v8Low; video ffwBPoKxlDI). His 2018 beginners' video sets 50 g of total carbs as the simple rule and counts total rather than net carbs (video UygKGoP_BtA). He also says ketosis itself is not the goal; low carb is, with ketosis as a perk for energy and hunger (video 1JbK1_ClDmY). See Net vs Total Carbs and the post Why 20 Grams of Carbs?.

Which rules are about ketosis and which are about health

Many keto rules you see online have nothing to do with ketosis. They may still be good ideas, but they are separate choices. Sorting them helps you keep the diet simple.

Rule Needed for ketosis? What it is really about
Keep digestible carbs low Yes The one rule that produces ketones
Eat enough protein No, but strongly advised Keeping muscle; staying full
Eat high fat No Fat fills the energy gap; amount depends on your goal
No grains No A personal or health choice
No dairy No A personal or health choice
Grass-fed butter or meat No Food quality preference
MCT oil No Optional; not required for ketosis
Drink water, get electrolytes No, but advised Comfort, especially in the first weeks

"High fat" is the rule people most often misread. Eating fat does not cause ketosis. Cutting carbs does. Fat is simply what makes up the rest of your energy once carbs are low and protein is set.

KetoDick on this: he says "the goal is not high fat, it's low carb," with fat filling the gap because protein has a ceiling (video cTGYIFOTPl8). He says eating fat does not "fire up" ketosis (video NUJNFG6lLWw), and separates extra rules such as no grain, no dairy and grass-fed only from what ketosis requires (video s_sNd1v8Low; video ffwBPoKxlDI). See the Protein and Fat chapters, and Is Keto a High-Fat Diet?.

What the research says keto does and does not do

Keto is studied mostly as a weight-loss and blood-sugar tool in adults with overweight, obesity or type 2 diabetes. A few key findings:

In short, keto works for many people, mostly by making it easier to eat less. It is not the only diet that works. The Fat Loss chapter covers why.

Who should talk to a doctor first

Ketosis is a normal state for most healthy adults. A few groups need medical input before starting, because the diet changes how medicines work or how the body handles ketones:

KetoDick on this: he tells anyone with a condition or on medication to review the plan with their doctor, especially dosing (video UygKGoP_BtA). See Who Should Talk to a Doctor.

The pages in this chapter

Page What it answers
What Ketosis Is What ketone bodies are, where they come from, and why your brain can use them
Ketosis vs Ketoacidosis Why diet-driven ketosis is not the dangerous condition, and who is at risk
Fat Adaptation Why weeks one to three can feel flat, and what changes after
What Can I Eat on Keto? Foods grouped by carb dose, not banned and allowed
Strict, Lazy, Dirty and Medical Keto The common versions, and how they differ

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Last verified: 2026-10-31