What Is Ketosis? Benefits, Risks & What To Expect in 2025

The keto diet has become a popular choice for people looking to change how they eat. It’s widely talked about, and you’ll find it mentioned in everything from recipe blogs to social media wellness posts. But while keto is a well-known approach, it’s also a restrictive one. This means it’s not suitable or sustainable for everyone.

At the heart of the diet is a process called ketosis. This is a natural metabolic state where your body switches from using carbs as its main energy source to using fat. When you're in ketosis, your liver produces compounds called ketones, which your body uses for fuel instead. Some people feel this shift helps them manage their appetite or feel more focused – but it doesn’t come without trade-offs.

This article is written under the guidance of a certified nutritionist. It’s designed to give you a clear, balanced overview of ketosis. You'll learn what it is, how it works, and what the current science says about the benefits and risks. If you're considering a low-carb diet (or just curious about what ketosis really means), this guide will walk you through the facts.

What Is Ketosis? 🤔

Ketosis is a natural metabolic state. It occurs when your body starts using fat instead of carbohydrates (glucose) for energy. This usually happens during prolonged fasting or very low-carb diets. When glucose is in short supply, your liver breaks down fat into molecules called ketone bodies, which become a primary energy source – especially for the brain and muscles¹.

The main ketones your body produces are:

• Beta-hydroxybutyrate (BHB)

• Acetoacetate

• Acetone

Entering ketosis requires a consistent drop in insulin levels. This allows the body to tap into stored fat. While many diets can increase ketone production, true ketosis refers to a metabolic state where ketones significantly replace glucose as the main energy source – something ketogenic diets aim to sustain¹.

How Does Ketosis Work? ⚙️

Under normal conditions, your body relies on glucose from carbohydrates for energy. When you eat carbohydrates, your body breaks them down into glucose. Extra glucose is stored as glycogen in the liver and muscles. When your carb intake drops, glycogen stores are depleted. Then your body turns to fat for fuel.

Here’s what happens next:

1️⃣ Fatty acids are released from fat cells into the bloodstream.

2️⃣ These travel to the liver, where they undergo beta-oxidation, producing a molecule called acetyl-CoA.

3️⃣ Acetyl-CoA is then converted into ketone bodies through a process called ketogenesis.

This process ramps up when insulin is low. That’s because insulin normally blocks fat breakdown. So when insulin levels drop (during fasting, carb restriction, or prolonged exercise) your body is free to burn fat for fuel. 

The liver doesn’t use ketones itself (it doesn’t have the enzyme to do so). Instead, it releases them into the blood, where they travel to other tissues – like the brain, heart, and muscles – to be used as energy¹.

Ketosis vs. Ketoacidosis 🆚

Although they sound similar, ketosis and ketoacidosis are very different. Ketosis is a natural metabolic state where the body burns fat for fuel. It happens during low-carb diets, fasting, or prolonged exercise, and insulin is still present to keep things in balance.

Ketoacidosis, on the other hand, is a dangerous condition – most often seen in people with type 1 diabetes – when ketone levels rise uncontrollably due to a lack of insulin. This leads to a buildup of acid in the blood and can be life-threatening without emergency treatment².

Signs & Symptoms of Ketosis 🪧

How do you know if you're actually in ketosis and not just cutting back on carbs? When your body shifts into ketosis, it sends out some telltale signs. Some feel great, others… not so much, especially at the start. 

Here's what to look out for: