Although the low-carb, high-fat keto diet was originally designed to treat epilepsy, many people are turning to it as a way of losing weight.
According to some research, it offers several advantages over other diets, including making it easier to burn the stored body fat, keeping your metabolism going (the calories you burn at rest), and feeling satiated with fewer calories (1, 2, 3.). ).
Even so, you may be wondering how much weight you are likely to lose in your first week on keto. Many people report extreme weight loss when they first start dieting. However, a large part of this is due to water losses.
This article describes how much weight you are likely to lose in your first week of keto.
With keto, you strictly limit your carbohydrate intake, usually to 50 grams or less total carbohydrates per day or 25 grams or less net carbohydrates, which is total carbohydrates minus fiber.
For most people, carbohydrates are the body’s primary source of energy. When you cut back on carbohydrates, your body burns the stores of carbohydrates in your muscles and liver – called glycogen – usually within a few days (4, 5).
After that, your body goes into a metabolic state called ketosis, in which it uses ketones, which are broken down from dietary fat or stored body fat, as its main source of fuel (4, 5).
That shift of depleting your glycogen stores and switching to ketones usually takes less than a week. However, it may take longer for some people (4, 5).
Many people notice dramatic weight loss during this transition period after starting the keto diet for the first time, but most of this is due to changes in water weight (6).
When you limit the carbohydrates on keto, your body quickly burns glycogen, the carbohydrates stored in your liver and muscles. After your glycogen stores are depleted, switch to burning fat. Many people notice dramatic weight loss during this transition.
The glycogen stored in your muscles and liver is bound to water, usually in a ratio of 3 grams of water per gram of glycogen (6).
When you burn these stored carbohydrates, that water is excreted in your urine or sweat (6).
Hence, after you start keto disease, you may find yourself urinating more often and feeling much more thirsty than normal. You can also notice large weight losses, which are mostly weight losses from water (6, 7).
Depending on your size and water weight, this weight loss can vary. Anecdotally, people report losses of 1 pound (0.5 kg) to 10 or more pounds (5 kg) within the first week.
The taller you are, the more water weight you are likely to lose after starting keto. However, it is unlikely that much of that initial weight loss will be fat loss.
However, once you step into ketosis, it is much easier to use your own stored fat for energy, which is one reason why the keto diet can be beneficial for weight loss (3).
When you burn glycogen, your body releases the water that is bound to it. Much of your early weight loss is likely due to these water losses. Even so, when you are fully in ketosis, you will burn more stored body fat.
Many people use the keto diet for weight loss, and there are several online reports of dramatic weight loss shortly after starting the diet.
This is likely mainly water weight as as your body burns your carbohydrate stores it releases the water that was bound to those carbohydrates.
Once you’re fully into ketosis, your weight loss will likely slow down, but it’s likely more fat than water.