Low-Carb Diet: How Much Weight Can You Lose On Keto?

The keto (short for ketogenic) diet has been around for centuries. A hundred years ago, the endocrinologist Rollin Woodyatt found that the liver produces ketone bodies (acetone, β-hydroxybutyrate, and acetoacetate) when a person is fasting or following a rich-fat, low-carb diet.

Back then, fasting was part of childhood epilepsy treatment¹. Since changing a person's diet was easier than fasting, a keto diet became a preferred therapy for epilepsy.

Over the past century, the ketogenic diet has been studied closely for its potential to treat other conditions, including diabetes, cancer, and Alzheimer's. Recently, it has been gaining popularity as a weight-loss strategy.

So how much weight can you lose on keto? Let's take a closer look.

How does a ketogenic diet work?

The preferred fuel for your body is glucose (sugar), which comes from carbohydrates. When you eat fruits, veggies, grains, and legumes, you obtain fuel that keeps your body functioning.

The keto diet forces your body to switch from sugar to ketone bodies that your liver produces from stored fat in energy production. The metabolic state when your body is using predominantly ketone bodies instead of glucose is called ketosis.

It usually takes several days to achieve ketosis. The exact time depends on your resting metabolic rate, body fat percentage, physical activity level, and, especially, daily carb intake.

How to lose weight on keto

For ketosis to begin, you can't eat more than 20–50 grams of carbohydrates daily. However, the exact number depends on your individual traits.

Carbohydrates

To consume fewer carbs, you need to cut grains, candy, and sugary soft drinks from your diet. You also need to eat fewer fruits and veggies.

In fact, your vegetable consumption should be restricted to leafy greens, cauliflower, broccoli, asparagus, cucumbers, celery, and a few other options. For fruits, you should limit yourself to berries.

Fats

While you can consume some unsaturated fats like almonds, walnuts, olive oil, avocados, and tofu, you should focus on bringing a lot of saturated fats into your diet. They include coconut oil, butter, cocoa butter, and lard.

Proteins

Protein is allowed in a keto diet. The best protein for ketosis contains a lot of saturated fat, such as beef, bacon, and pork.

The commonly recommended² ratio for a keto diet is 70–80% fat, 5–10% carbohydrate, and 10–20% protein.

How much weight can you lose on keto?

When you are in ketosis, you are actively burning stored fat, which results in weight loss. However, the amount of weight you can lose depends on several factors:

Caloric intake

A keto diet can be very high in calories. The amount of weight you lose depends on how well you control your caloric intake. 

General health

If you are overweight, have thyroid problems, or suffer from blood sugar issues, it may take more time for the weight loss to kick in. More importantly, ketosis may sometimes be dangerous for people with chronic health problems.

Metabolism

Since the time it takes for different people to reach ketosis varies, some start losing weight faster than others.

Lifestyle

Sleep quantity and quality, water consumption, and activity levels can affect your weight loss on keto.

Consistency

People who religiously stick to the keto diet can achieve better weight loss results.

If a person follows the 75% fat /20% carb/5% fat keto diet, average results may look like this:

• Weeks 1–2: rapid weight reduction phase due to water loss – up to ten pounds

• Weeks 2–4: standard weight reduction – between one and two pounds per week

• After the first month – slow weight loss – around one pound per week

While many people expect faster results, one to two pounds per week³ is a healthy rate. Consistent rapid weight loss could lead to serious health problems.

How fast can you lose weight on keto?

The speed of weight loss depends on your initial body mass index (BMI) and body fat indications. People with a higher BMI tend to lose more weight at the beginning of a keto diet.

Once you begin dieting and start burning stored carbs, water that binds them leaves your body. You will likely experience frequent urination.

As the excess water makes its exit, you may notice rapid weight loss. This usually happens within the first two weeks of starting the diet. As you continue your keto diet, the weight loss rate will substantially decrease.

A study⁴ found that you could lose weight on keto faster than you would on a low-fat diet. However, this doesn't mean that you will see drastic results. The stories you may have heard about significant weight loss on a keto diet usually come from people who are on it for one or two weeks.

What are the risks of keto?

Changing the way your body works can come with a variety of risks. For this reason, it’s important to consult a doctor before you start the keto diet to adjust your metabolism. While it can be effective for some people, this diet can be dangerous to others in a number of different ways:

Heart disease

Since the keto diet involves eating large amounts of saturated fats, it could increase your risk of developing heart disease.

Nutrient deficiency

Once you start limiting veggies, fruits, and grains, your body stops getting essential nutrients, such as vitamins B and C, magnesium, selenium, and others. This could lead to serious health problems, including heart disease, infertility, cognitive decline, psychological conditions, and much more. Pregnant women may not get sufficient folic acid, which could lead to birth defects.

Liver disease

If you have existing liver conditions, forcing the organ to metabolize excess fat could worsen them.

Kidney problems

A keto diet could overload your kidneys as they work to metabolize proteins.

Constipation

Since you are reducing fibrous foods (grains, vegetables), you may experience constipation.

Reduced muscle mass

If you are restricting calorie intake on a keto diet at the expense of protein-rich foods, you could start losing muscle mass.

Ketoacidosis

In people with type 1 diabetes, a keto diet could cause the body to store too many ketones. This could cause the blood to become acidic and damage the liver, kidneys, and brain. Rarely, ketoacidosis occurs in healthy people.

According to a study⁵ published in Frontiers in Nutrition, a long-term keto diet may do more harm than good. It's unsafe for people with liver problems, kidney disease, and diabetes. Besides this, the diet contains many foods associated with high cancer risks.

Even if a person is healthy,  keto’s macronutrient proportion may make it unsafe for continuous use. Although a relevant study⁶ has demonstrated that increasing the fat to carbohydrate ratio in the diet is beneficial, the safety of the fat amount usually presented in a keto diet is still not supported. After dieting for a few weeks, consider discussing a less aggressive approach with your doctor.

What are the challenges of losing weight on keto?

While keto can help you lose weight, sticking to this diet is often a challenge. Extreme carbohydrate restriction could cause unpleasant symptoms such as hunger, fatigue, mood swings, headaches, dizziness, and constipation.

Symptoms will subside with time. However, they can last for weeks in some people and, in the end, will be replaced with cravings for carbs.

It's important to understand that while effective, a keto diet isn't a fast way to lose weight. Just as with a low-calorie diet, you will notice drastic weight loss in the first few weeks, followed by a stable decrease.

The lowdown

The keto diet changes the way your metabolism works by encouraging it to use ketone bodies instead of glucose for energy production. In the first couple of weeks, it’s possible to lose up to ten pounds. After that, you could be losing one to two pounds per week.

Since keto may come with serious side effects, speaking to your doctor or a dietician before starting it could prevent unfortunate consequences for your health.