Can I Lose 10 Pounds in the First Week of Keto?

Have you heard that you can lose 10+ pounds in your first week of keto? The truth is you can. In fact, if any of you reading this have tried keto yourself then you have probably experienced pretty rapid weight loss when first starting keto yourself.

The problem is that this leads many to being skeptical. No way you can lose 10 pounds in a week or if you can there’s no way its good for you. To help ease the skepticism, it’s important to understand where this weight loss is coming from.

Why Does Rapid Weight Loss Occur on Keto?

The weight lost during your first few weeks on keto comes from water, glycogen, and fat. However, the primary contributor to the rapid weight loss is water. Check out this infographic I made to help break this down.

Why is Weight Loss So Rapid on Keto infographic.jpg

No, of course all of that 10 pounds you lost in your first week is not fat. That would be pretty insane! Most of it is water. If you look at the bottom of the infographic above, you can see a simple explanation of why water loss occurs on keto.

To go a little more in depth, when you stop eating carbohydrates, blood glucose lowers causing a subsequent drop in insulin levels. This makes the pancreas secrete glucagon, which signals for stored fatty acids to be released from adipose tissue and into the blood where they can circulate and be taken in by various cells and used for energy. However, some fatty acids make it to the liver and are used for ketogenesis, which results in ketone molecules being produced from fat and shuttled out into the bloodstream, where they can travel to cells. Initially, these ketones have to help activate the transporters responsible for opening the doors for ketones to get in. This process can take some time and is one of the reasons why you see an increase in blood ketones, but a lag time before the benefits of ketosis are felt.

No, you did not need the above information to learn why water loss is rapid on keto but I think understanding the process of keto is important so I slid it in there hoping you’d read it ¯\_(ツ)_/¯

What you do need to know about your insulin levels lowering is that your kidneys are responding by dumping a lot of water leading to rapid weight loss.

Is Rapid Water Loss on Keto Dangerous?

No. While many people may use this as support for keto being dangerous, it’s not. But it is one of the reasons why you experience most keto flu symptoms. When you are rapidly dropping water you are prone to dehydration and electrolyte depletion which is a common trigger of many keto flu symptoms, especially the popular brain fog. This is why drinking plenty of water and replenishing electrolytes is so important on a ketogenic diet.

Ketogenic Diet and Brain Fog.jpg

If you are new to keto or are thinking about starting, you may be thinking, “when will I start burning fat then? Great question.

When Do I Start Burning Fat on Keto?

Pretty much right away. Once you start to lower your insulin levels you will turn on fat burning. How long it takes for this to occur is different for everyone depending on your level of insulin sensitivity when starting keto. If you want to learn more about insulin sensitivity, check out my YouTube video on Insulin Resistance.

During your first week of keto you are still burning fat. It’s just not contributing to all of the weight you are losing. As you continue following keto you will keep improving your fat burning abilities and will start to notice more steady realistic weight loss like 0.5-2 pounds per week.

What About Glycogen Loss at the Start of Keto?

If you noticed in the first infographic, glycogen was also a contributor to weight loss at the start of keto. Glycogen is our bodies stored form of carbohydrate. When you first stop eating carbs, your body will likely respond by burning through most of is stored glycogen. It is not a massive supply but it is enough that it can contribute to weight loss, especially since water is also stored with glycogen.


In summary, you lose a lot of weight when you first start keto because of water loss. This is not a bad thing or anything you need to worry about. It is a natural process that occurs as we become adapted to a ketogenic diet. Drink plenty of water and supplement with electrolytes!

Christopher Irvin