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:

Not everyone experiences every symptom, and some signs (like keto breath or fatigue) may fade over time. If you're unsure, checking your ketone levels is the most reliable way to confirm ketosis.

What to Eat on the Keto Diet? 🍴

When you're following a keto diet, you need to be mindful of your carb intake. You’ll need to avoid foods that are high in carbohydrates to stay in ketosis. That means cutting out bread, pasta, rice, and potatoes, as well as sugary snacks and most processed foods. You’ll also want to avoid high-carb fruits like bananas and grapes and stick to low-sugar options instead.

To stay in ketosis, your daily meals should follow a specific macronutrient balance:

✅ High Fat (70-80%) This is your main fuel source. Load up on healthy fats from avocados, nuts, seeds, olive oil, butter, fatty fish, eggs, and cheese.

✅ Moderate Protein (15-25%) Include protein-rich foods like meat, poultry, seafood, eggs, and dairy, but don’t overdo it. Too much protein can be converted into glucose through a process called gluconeogenesis, which may disrupt ketosis.

✅ Low Carbs (5-10%) Limit your carbohydrate intake to around 20-50g of net carbs per day. Focus on non-starchy vegetables such as leafy greens, cauliflower, zucchini, and broccoli. You can also include small servings of berries, nuts, and seeds.

What Does a Day on Keto Look Like? ☀️

Keto-Friendly Diet on a Budget: 5 Top Tips ✅

A keto diet doesn’t have to break the bank. While some might assume that low-carb, high-fat eating is expensive, there are plenty of ways to keep your meals affordable without compromising on the benefits. Here's how you can eat keto without overspending:

How Long Does It Take to Get Into Ketosis?

If you’re aiming to enter ketosis, sharply reduce carbs and increase fat intake. This will help your body switch from burning glucose to burning fat for fuel. If you're new to the diet, gradually cutting carbs may be easier to manage than going cold turkey (or cold carbs!) Also, gradually increasing fats will help your body adjust smoothly.

Typical Timeline to Ketosis ⏱️

The time it takes to enter ketosis can vary, but here’s a general timeline:

• 0-12 hours: Your body begins using up stored glucose (glycogen) for energy.

• 12-24 hours: Glycogen stores start depleting, and your body starts ramping up fat-burning to compensate.

• 24-48 hours: Ketone production begins as glycogen runs low. Your body starts using fats as its primary fuel source.

• 2-7 days: Full ketosis is reached, and you’ll have measurable ketones in your blood or urine.

How fast you enter ketosis depends on factors like age, diet, activity level, and metabolism. Younger, more active people with lower carb intake and faster metabolisms typically get there quicker, while poor sleep and high stress can slow the process.

To enter ketosis faster, try intermittent fasting to burn through glycogen stores more quickly. Keep carbs under 50 g per day (about a cup of pasta or 3 slices of bread) and add regular exercise to help deplete glycogen and boost fat-burning.

As your body flushes out excess water when entering ketosis, maintaining an appropriate electrolyte balance (sodium, potassium, magnesium) is crucial. This helps prevent dehydration, muscle cramps, and the "keto flu" symptoms some people experience during the early stages of the diet³.

Testing for Ketosis 🧪

To confirm that you’re in ketosis, you can use various testing methods:

• Urine strips: Affordable and easy to use but less accurate as you become fat-adapted.

• Blood meters: More accurate, measuring ketone levels in your blood for precise results.

• Breath analyzers: These measure acetone (a type of ketone) in your breath, providing a non-invasive way to check ketosis.

How Do You Know When You’re Out of Ketosis? 

If you eat too many carbs or too much protein, you might exit ketosis. Or if your body isn’t burning fat efficiently, you may move out of ketosis. Here’s how to tell:

🥑 Weight Loss & Fat Burning

Ketosis shifts your body’s primary fuel source from glucose to fat. This encourages the use of stored fat for energy. Many people also experience a drop in appetite, possibly due to changes in hunger hormones like ghrelin and leptin. In the first few days, weight loss is often due to water loss as glycogen stores are depleted.

While these early changes can be motivating, the long-term sustainability of weight loss on a ketogenic diet is still debated. Its overall health impact compared to more balanced diets, such as the Mediterranean diet, isn’t fully understood. More high-quality, long-term studies are needed to confirm whether keto is an effective and healthy approach for weight management over time⁴.

🩸 Blood Sugar Control & Insulin Sensitivity

Some research suggests it can improve insulin sensitivity, particularly in people with type 2 diabetes. This is likely due to the reduced intake of carbohydrates, which helps stabilize blood glucose levels. However, the keto diet isn’t a one-size-fits-all solution and is not universally recommended for diabetes management⁵.

It’s essential to follow this type of diet under medical supervision, especially when managing a condition like diabetes. Long-term effects are still being studied, and comparisons with other diets – such as plant-based or Mediterranean approaches – show mixed results. More robust clinical trials are needed to determine how ketosis stacks up in the long run.

🎯 Mental Focus, Clarity, & Energy

Many people report feeling more mentally sharp and focused on keto. This may be partly due to more stable blood sugar levels and the brain’s use of ketones as a clean-burning fuel. That said, these improvements could occur with any shift from a highly processed Western diet to a whole-food-focused one⁶. 

Compared to more balanced diets like the Mediterranean approach, the high fat intake on keto may not offer any unique cognitive benefits. It could also make you feel heavy or sluggish.

⚡ Epilepsy Treatment

The ketogenic diet is a medically approved treatment for drug-resistant epilepsy. It’s especially effective in children. It has been used since the 1920s and remains one of the clearest evidence-backed uses of ketosis in clinical settings. Its effectiveness for other neurological conditions is still being explored⁷.

🧬 Neurological Conditions

Early research is exploring how ketosis might support brain health. For example, in conditions like Alzheimer’s disease, Parkinson’s, and traumatic brain injuries. While the idea of using ketones to fuel a compromised brain is intriguing, current evidence is limited and preliminary. Clinical trials are ongoing, and it’s too early to draw firm conclusions⁸.

🧠 Mental Health

There is emerging interest in how ketogenic diets might affect mood disorders. These include depression, bipolar disorder, and anxiety. Some case reports and pilot studies suggest possible improvements, likely linked to brain energy metabolism and inflammation. However, this area is in its infancy, and more rigorous studies are required to verify benefits and rule out risks⁹.

❤️ Longevity & Heart Health

Some early findings sound promising. Proponents of ketosis suggest it may reduce mortality risk and improve cardiovascular markers like triglycerides and HDL cholesterol. However, these claims are mostly based on observational studies or small clinical trials, so more robust, long-term research is needed to draw firm conclusions¹⁰. 

The factor that makes the biggest difference is really your specific food choices. A poorly planned keto diet can actually be quite unhealthy, especially if you are consuming more unhealthy fats than healthy ones¹¹.  

The high intake of saturated fats often associated with keto is still controversial, and long-term cardiovascular effects remain uncertain. A balanced diet rich in whole grains, legumes, and healthy fats is still the gold standard in heart health guidelines.

The Ketogenic Diet: Long-Term Considerations 🔮

Ketosis can offer short-term benefits. However, there are several long-term factors to keep in mind – especially if you're considering staying on the diet for more than a few months.

• Nutrient deficiencies: Restricting carbs can limit your intake of key nutrients like fiber, vitamin C, magnesium, and certain B vitamins¹². Without careful planning, you may fall short on these essentials, especially if you're not eating a variety of non-starchy vegetables and fortified foods¹³.

• Cholesterol and heart health: A high intake of saturated fat – common on keto – can raise LDL ("bad") cholesterol in some people. While some keto followers see improved triglycerides and HDL, the long-term effects on heart health remain unclear, and experts continue to debate whether these improvements outweigh potential risks¹⁴.

• Long-term sustainability: Strict keto can be hard to maintain. Many dietitians recommend more balanced, whole-food diets like the Mediterranean diet for long-term health. These approaches are more flexible, include a wider range of nutrients, and are often easier to stick with.

Some experts suggest that a moderate low-carb approach might offer similar benefits. This approach avoids the extreme restrictions of keto. That said, for most healthy individuals, neither strict keto nor very low-carb diets are necessary. Plus they’re usually not the first choice for general wellness.

Should you take breaks from keto?

Yes, it’s a good idea. Taking breaks or cycling in and out of keto may help support mental and metabolic flexibility, reduce stress around food choices, and give your body a chance to replenish nutrients. This kind of flexible approach is often more realistic – and healthier – in the long run.

Practical Tips for Success 🙌

🎉 Social events and dining out: Choose grilled meats, salads, and veggies. Bring a keto dish to gatherings.

💰 Budget keto tips: Buy affordable proteins like eggs and chicken. Shop seasonal and bulk, and meal plan.

🍽️ Meal delivery: Use services like Factor for quick, keto-friendly meals with no prep.

🏃‍♂️ Exercise on keto: Stick to light activity (like walking) during the first week of adaptation.

📈 Track more than weight: Watch energy, focus, and ketone levels – not just the scale.

🌙 Keto for shift work: Pack keto snacks, stay hydrated, and mind your electrolytes.

✈️ Keto while traveling: Bring portable snacks and research low-carb options ahead.

👨‍👩‍👧 Family meals: Use flexible meal delivery services to accommodate different dietary needs.

Keto & Different Dietary Needs 🌱

Metabolic flexibility is your body's ability to switch between burning carbs and fat for fuel. While keto can improve this, it’s not the only way. Combining keto with a plant-based diet can be tricky since plant-based foods often rely on carbs, which clashes with keto’s strict carb limits.

Many also debate whether a strict keto diet is the best approach. "Keto cycling," or alternating between keto and higher-carb periods, offers some flexibility while still encouraging fat burning. However, more research is needed, especially for those following plant-based or flexible diets.

Keto & Different Fitness Levels

Your fitness level can impact your experience with keto. Sedentary individuals may adapt more easily, as they don’t rely on glycogen for energy. However, active individuals, especially athletes, might experience a more challenging transition as their body adjusts to burning fat instead of carbs, leading to temporary dips in performance and energy¹⁵.

Athletes may see a decline in performance, particularly for high-intensity activities, but many report improved endurance over time as their bodies become better at using fat for fuel. While some athletes thrive on keto, others may struggle during the adaptation phase. More research is needed to understand its long-term impact on athletic performance¹⁶.

FAQ

Is it good to be in ketosis?

Yes, ketosis can be beneficial for some people. It shifts the body to burn fat for energy, which may aid in fat loss. However, it's not suitable for everyone and should be approached with caution. Consult a healthcare professional before starting a ketogenic diet.​

How do I know I am in ketosis?

You can confirm ketosis through blood ketone meters, which measure ketone levels in the blood. A level between 0.5 and 3 mmol/L indicates nutritional ketosis. Symptoms like fruity breath, increased thirst, and reduced appetite may also suggest ketosis.

How can I get into ketosis quickly?

To enter ketosis quickly, reduce your carb intake to 50 grams or less per day. Incorporating intermittent fasting, such as fasting for 12-16 hours, can accelerate the process by depleting glycogen stores. Increasing physical activity also helps deplete glycogen and promotes fat burning.

Is ketosis safe for everyone?

No, ketosis isn't safe for everyone. Individuals with liver, pancreas, thyroid, or gallbladder issues should avoid it. There are some risks and side effects. For example, it can cause low blood pressure, kidney stones, constipation, and nutrient deficiencies. Consult a healthcare provider before starting a ketogenic diet.

How much weight can you lose on keto?

Initial weight loss on keto often includes water weight due to glycogen depletion. It's common to lose 6-10 pounds in the first week. However, this is primarily water loss, not fat loss. Sustained fat loss varies and depends on individual factors.

References

1. https://www.ncbi.nlm.nih.gov/books/NBK493179/

2. https://www.cdc.gov/diabetes/about/diabetic-ketoacidosis.html

3. https://www.ncbi.nlm.nih.gov/books/NBK541123/

4. https://pmc.ncbi.nlm.nih.gov/articles/PMC6371871/

5. https://pmc.ncbi.nlm.nih.gov/articles/PMC9919384/

6. https://pmc.ncbi.nlm.nih.gov/articles/PMC8840718/

7. https://pmc.ncbi.nlm.nih.gov/articles/PMC6361831/

8. https://pmc.ncbi.nlm.nih.gov/articles/PMC9102882/

9. https://www.sciencedirect.com/science/article/pii/S0165178124001513?via%3Dihub

10. https://www.nature.com/articles/s41598-024-73384-x

11. https://pubmed.ncbi.nlm.nih.gov/38232923/

12. https://www.researchgate.net/publication/332098774_Nutritional_Deficiencies_of_Ketogenic_Diets

13. https://pmc.ncbi.nlm.nih.gov/articles/PMC4588743/

14. https://pmc.ncbi.nlm.nih.gov/articles/PMC7008768/

15. https://pmc.ncbi.nlm.nih.gov/articles/PMC6863116/

16. https://ajcn.nutrition.org/article/S0002-9165(22)01221-7/fulltext