Keto First Week: What to Expect Day by Day

Quick answer: Your first week on keto is mostly water, cravings and rough sleep. You'll likely see the scale drop a few pounds, and that drop is real, but it's water from your glycogen stores, not fat. Don't celebrate it and don't panic when it slows. Eat until you're full, keep carbs low, drink water, and judge nothing until well past day seven.

In this article

• The first days: the glycogen drain
• Midweek: cravings and the slump
• The end of week one: the scale and the sleep
• What to do this week
• Who should call their doctor first
• What the research says
• KetoDick's take
• Key takeaways

A note on "day by day": nobody's body runs to a calendar this precise, and KetoDick's own schedule is by the week, not the day (video uDw65ERtsA0). So treat the stages below as an order of events, not appointments.

The first days: the glycogen drain

When you cut carbs, your body first burns through the sugar in your blood and the glycogen stored in your liver and muscles. Glycogen is stored with water, at about two grams of water for every gram of glycogen (video uDw65ERtsA0).

Here's the kitchen-table version. In his 2018 basics he gives about 700 g of glycogen plus 1,400 g of water, about 4.4 lb (video UygKGoP_BtA). In another video he says most people drop about three pounds of water in week one, and heavier people may see seven to ten (video uDw65ERtsA0).

That's why you'll pee more. See why you pee so much on keto and water weight.

Midweek: cravings and the slump

Somewhere in here, most people feel bad. Your glycogen is low, but your liver hasn't yet built up the machinery to run comfortably on ketones. You're between fuel tanks. He describes week one and two fatigue as exactly that gap: glycogen gone, liver not up to speed, not fat adapted yet (video 9r2Y74AnjUQ).

The cravings show up too. He calls most of what people label "keto flu" withdrawal from sugar and carbs, and says that's more his opinion than science (video 9r2Y74AnjUQ). Either way, it's normal, and it passes. More in how to stop sugar cravings.

Watch for cramps. He treats those as a separate problem, probably electrolytes, not part of the slump (video 9r2Y74AnjUQ).

The end of week one: the scale and the sleep

By the end of the week the scale has probably moved, and your sleep may be off. In his own first month he reported energy crashes and sleep irregularities, but no cramps, and about 12 pounds down by day 28, which he said was mostly water (video 9Hk0jRb_9Es).

The water point matters because it comes back. He says that water returns almost immediately on a high-carb meal (video uDw65ERtsA0). So if you see three pounds go in week one and two come back after a pizza, nothing happened to your fat. See can't sleep on keto.

What to do this week

• Eat until you're full. In weeks one and two he says to eat until full and avoid carbs, and not to try to hit a calorie target (video DoSUgIr2rNo).
• Count carbs, and only carbs. In month one, he says, that's all you have to count (video DoSUgIr2rNo).
• Stay off the scale. He says to ignore the scale and calories for at least the first two weeks (video DoSUgIr2rNo), and elsewhere to skip it for 30 days (video uDw65ERtsA0). See weighing yourself in month one.
• Drink water. Many people lose the calories they used to drink; flavour drops are an option (video DoSUgIr2rNo).
• Get your salt from food. He suggests salted broth or bouillon once or twice a day, and light salt for potassium (video UygKGoP_BtA).
• Expect keto breath. He says keto breath and body-odour changes are real side effects (video DoSUgIr2rNo). It's not a sign anything is wrong.
• Use the week to learn. Weeks one to three are for learning new foods, shopping, oils, sweeteners and flours (video DoSUgIr2rNo).

Who should call their doctor first

This part isn't boilerplate. Cutting carbs changes blood sugar and fluid balance quickly, and some medications are dosed for the old you.

• Diabetes medication or blood pressure medication: review the plan and the dosing with your doctor before you start (video UygKGoP_BtA). See medications.
• Thinking about potassium or sodium pills: he says to talk to a doctor before supplementing, because imbalances can be serious (video 9r2Y74AnjUQ).
• Kidney disease or pregnancy: check with your doctor before changing your diet this sharply.

What the research says

• The early symptoms are usually temporary. An analysis of online posts found reported "keto flu" symptoms clustered in the first weeks and were mostly described as transient (Bostock et al., 2020).
• Insulin and salt are linked. An insulin infusion, with glucose held steady, cut how much sodium, potassium and phosphate healthy men excreted (DeFronzo et al., 1975). That study ran the other direction from keto, raising insulin, but it shows insulin affects how the kidneys hold onto salt, one reason fluid shifts when insulin falls.
• The liver makes ketones under insulin's control. The NIH's StatPearls chapter describes ketogenesis in the liver, regulated by insulin and glucagon (Dhillon & Gupta, StatPearls).
• The switch takes weeks, not days. In prolonged fasting, ketones replaced glucose as the brain's main fuel only after weeks (Owen et al., 1967). That was fasting, not keto, but it fits the idea that day seven is too early to judge.

KetoDick's take

I've said the typical keto schedule is week one water weight, weeks two and three upset stomach and stalling, and real fat loss from about week four onward (video uDw65ERtsA0). You should know going in that the early part is like that.

I've also said you're not really on the diet until week three, four or five, so how you feel on day ten is irrelevant (video cTGYIFOTPl8). Give it a full 60 days before you decide (video uDw65ERtsA0).

Key takeaways

• Week one weight loss is mostly glycogen water, a few pounds for most people.
• Expect a slump, cravings and rough sleep; cramps are a separate electrolyte question.
• Eat to fullness, count carbs only, drink water, salt your food or have broth.
• Stay off the scale; it can't tell you anything useful yet.
• On diabetes or blood pressure medication? Talk to your doctor before day one.

Related

• Guide chapter: Starting keto · Month one · Water weight · Timeline · Keto flu
• Blog: How long does keto flu last? · Can't sleep on keto · Why do I pee so much on keto? · Weighing yourself in month one
• Videos: The keto weight loss schedule · Keto update 1 · Setting up MyFitnessPal · It's not keto flu