Keto made easy

What Happens If You Cheat on Keto?

Quick answer: It depends on when. In your first few weeks, before you're fat adapted, a big carb meal refills some glycogen and puts you back near the start of the adaptation clock. Once you're adapted, one meal can't refill your glycogen stores, so you're usually back in ketosis within a day. Expect the scale to jump from water, and maybe an upset stomach. One meal is a meal, not a failed diet.

In this article

What a carb meal does, step by step

Start with the mechanism. On keto your insulin runs lower, your glycogen tanks are mostly empty, and your liver makes ketones from fat. Eat a plate of pasta and three things happen:

  1. Blood glucose rises and insulin goes up with it.
  2. Insulin tells the liver to turn ketone production down. The biochemistry texts describe ketogenesis as regulated by insulin and glucagon (Dhillon & Gupta, StatPearls).
  3. The carbohydrate you didn't burn goes into glycogen storage, with water attached.

Then, as you go back to low carb, you burn that glycogen off, insulin drops, and the liver ramps ketone production back up. How long that takes depends mostly on two things: how much glycogen you refilled and how well adapted your liver already is.

Before fat adaptation: why it costs more

Fat adaptation is the part that takes weeks. KetoDick describes it as your liver enzymes building up over time, in about weeks three to four for most people, and nearly everyone by six to seven, on under 50 g of carbs (xyEZL0HuejI). Elsewhere he gives 2–4 weeks for thinner people and 3–8 for heavier ones (s_sNd1v8Low; see fat adaptation).

In that window you haven't built the machinery yet. So a cheat meal in week one or two doesn't just cost you a day. It refills glycogen you'd just finished burning, and you go back through the low-energy gap again. He explains ketosis as a bit like a chain reaction: once it's running, it keeps itself going more easily, and that's when cheat meals "aren't going to bother you as much," from the video (xyEZL0HuejI).

He puts the generic "feeling crappy" people call keto flu partly down to not having built up fat adaptation yet, and partly to lost salt and minerals (uXzscHudgt0). Each early cheat keeps you in that under-adapted stretch a little longer. So what you do in month one is simple: don't plan cheats. If you're hungry, eat more fat and protein instead of carbs.

After fat adaptation: the glycogen arithmetic

This is where his favourite kind of proof comes in. He says an adult man stores about 700 g of glycogen, and women should scale that down by about 25 to 35 percent (1vyxuWlxT5M). At about 4 calories per gram, 700 g is about 2,800 calories of stored carbohydrate.

Now run a cheat day through it. If you're in week three or four and eat 100 g of carbs in a day, you've put back at most 100 of those 700 grams, about a seventh of the tank. His point: there's no way a single 100 g day refills that and reverses adaptation (1vyxuWlxT5M). For a woman with roughly 450–525 g of storage (his 25–35 percent reduction), it's still about a fifth.

What can loosen adaptation, he says, is several days off in a row, like a holiday week, which gives your body time to refill glycogen and lean on glucose again (1vyxuWlxT5M). And his own example: he had a whole panini and a bag of chips and was back in ketosis later that same night, because he was well adapted (1vyxuWlxT5M).

The scale jump and the stomach ache

Two side effects catch people off guard.

The scale. Glycogen is stored with about twice its weight in water, and that water returns almost immediately when you eat a lot of carbs (uDw65ERtsA0). Using that ratio, refilling 100 g of glycogen brings back roughly 200–300 g of water, up to about two-thirds of a pound, plus the weight of the food itself still in your gut. That's not fat (gained weight overnight).

The gut. A viewer who had a bowl of cereal at three and a half weeks asked why she felt awful. His answer was the gut microbiome: the bacteria that lived on carbs have died back, and a sudden load of them causes distress. He says that's not you falling out of ketosis (xyEZL0HuejI). See keto and your gut microbiome.

Getting back on track

  1. Go straight back to your normal low-carb day. No punishment fast and no calorie crash.
  2. Move and drink water. After a weekend of drinking, his fastest way back is water and a morning walk to burn off the glycogen (xyEZL0HuejI). More in alcohol on keto.
  3. Ignore the scale for a few days. The water leaves as the glycogen goes.
  4. Count the carbs honestly. He's clear that one meal off is fine once you're adapted, but the carbs in a cheat still count toward your week (cTGYIFOTPl8).

If you take insulin or another glucose-lowering medicine, a cheat meal isn't just a diet question. Your dose was probably set around a low-carb pattern, and a big swing in carbs can push blood sugar the wrong way. KetoDick tells anyone on medication to go over the plan with their doctor, especially dosing (UygKGoP_BtA); see medications.

What the research says

The research pages don't include a trial that fed people one cheat meal and timed their return to ketosis, so there's no published "hours to recover" number to give you here.

What the literature does give is the mechanism. Ketogenesis happens in liver mitochondria and is regulated by insulin and glucagon (Dhillon & Gupta, StatPearls), which is why a carbohydrate load turns it down and why it resumes as insulin falls. The major review of ketone metabolism covers how ketones are made and used and how that's controlled (Puchalska & Crawford, 2017). Laffel's review describes ketone levels and how they're monitored with blood and urine tests (Laffel, 1999), which is the practical way to check where you are after a slip.

The glycogen figures and the timeline in this post are KetoDick's, from his videos, not trial measurements.

KetoDick's take

His frame is that a diet is what an organism eats over a period of time. An owl that ate a guinea fowl once doesn't have a guinea-fowl diet; it had a guinea-fowl meal (cTGYIFOTPl8). He'd rather you judge your eating over at least a week, and ideally a month (1vyxuWlxT5M).

He also separates a cheat from a planned higher-carb vegetable day. Past weeks three to five, he's comfortable with an occasional day built around a big salad or green beans, which he calls nutrient loading rather than cheating. Three days of soda, ice cream and cough drops is a different thing (1vyxuWlxT5M).

Key takeaways