What Is Ketosis? A Nutritionist Explains – The Keto Collective

Ketosis is a metabolic state where your body burns fat and produces ketones for energy instead of relying on glucose from carbohydrates.

I get asked about ketosis more than anything else at The Keto Collective. And I understand why. The word sounds medical. Slightly intimidating. Like something that should come with a warning label.

But here’s the thing. Your body already knows how to do this. It’s been doing it for thousands of years. Every time our ancestors went a day without food, their bodies flipped into ketosis and started burning stored fat to keep them alive. It’s a built in survival mechanism.

When you follow a ketogenic diet, you’re simply triggering that same switch on purpose. You cut the carbs, your liver starts converting fat into molecules called ketone bodies, and those ketones fuel your brain, muscles, and organs instead of glucose.People come to ketosis for all sorts of reasons. Weight loss is the big one. But I’ve also worked with clients chasing better blood sugar control, sharper mental focus, reduced inflammation, and even help with conditions like PCOS and type 2 diabetes.

A word of caution before we go any further. Ketosis is not suitable for everyone. If you have type 1 diabetes, kidney disease, liver problems, a history of eating disorders, or you’re pregnant, you need proper medical guidance before attempting a ketogenic diet. I’ll cover this in more detail below.

What is Ketosis?

Ketosis is a metabolic process where your body switches its primary fuel source from glucose to fat. When your carbohydrate intake drops low enough, your liver starts converting fatty acids into ketone bodies. These ketones then become the main energy source for your brain, heart, and muscles.

This happens naturally during fasting, prolonged exercise, or when following a ketogenic diet. Blood ketone levels rise, typically reaching 0.5 to 3.0 mmol/L during nutritional ketosis.

And yes, this is completely different from ketoacidosis. I’ll explain the distinction properly later, but the short version: nutritional ketosis is a controlled, safe metabolic state. Ketoacidosis is a dangerous emergency that primarily affects people with type 1 diabetes. They are not the same thing. Not even close.

A bit of history that most people don’t know. The ketogenic diet wasn’t invented for weight loss. It was first proposed by Dr. Russell Wilder at the Mayo Clinic in 1921 to treat epilepsy in children, inspired by earlier observations from Dr. Marie that seizure severity reduced during fasting. By 1930, the ketogenic diet was widely used as a standard epilepsy treatment, and it worked remarkably well. Decades later, researchers started noticing all the other benefits: fat loss, blood sugar control, reduced inflammation, improved neurological function. The weight loss crowd caught on in the early 2000s and the rest is history.

I find that fascinating. A diet designed to help children with seizures ended up being one of the most effective fat loss strategies we have. Science has a funny way of working sometimes.

Ketosis: Definition and Key Facts

What You Need to Know About Ketosis

Definition

Ketosis is a metabolic state where your body burns fat instead of carbohydrates for fuel, producing ketone bodies

How to Induce Ketosis

Restrict carbs to 20 to 50g daily, or combine with intermittent fasting

Time to Enter Ketosis

2 to 7 days on a strict low carb diet

Blood Ketone Range

0.5 to 3.0 mmol/L for nutritional ketosis

Top Benefits

Weight loss, stable blood sugar, reduced hunger, mental clarity

Main Risks

Keto flu, electrolyte imbalances, not safe for type 1 diabetes without supervision

Who Should Avoid Ketosis or Get Medical Supervision

Do not attempt ketosis without medical guidance if you have:

• Type 1 diabetes (risk of diabetic ketoacidosis)

• Type 2 diabetes on insulin or sulfonylureas

• Kidney disease or impaired kidney function

• Liver disease

• History of eating disorders

• Pregnancy or breastfeeding

• Gallbladder disease or no gallbladder

• Family history of high cholesterol or heart disease

If you’re on any medication, especially for diabetes or blood pressure, talk to your doctor before starting. The diet can change how your body responds to medication and dosages may need adjusting.

I put this section near the top on purpose. Ketosis is safe for most healthy adults. But “most” isn’t “all” and I’d rather you check than end up in trouble.

How Does Ketosis Work?

Let me walk you through what actually happens in your body. Because understanding the mechanism makes everything else click into place.

Under normal conditions, you eat carbohydrates. Your digestive system breaks them down into glucose. Insulin arrives, shuttles that glucose into your cells, and your cells burn it for energy. Simple enough.

On a ketogenic diet, you’ve dramatically cut the carbs. Your blood glucose drops. Your glycogen stores (that’s glucose stored in your liver and muscles) start running low. Your body needs fuel but there’s barely any glucose available.

This is where the magic happens. Your liver starts breaking down fat, both from food and from your body’s fat stores, into fatty acids. It then converts those fatty acids into three types of ketone bodies:

Beta hydroxybutyrate (BHB) is the most abundant ketone and the one measured by blood meters. This is the workhorse of ketosis.

Acetoacetate is what urine strips detect. It’s the ketone your kidneys filter out, which is why beginners often start testing with wee strips.

Acetone is the one you can smell on your breath. It’s the reason people in ketosis sometimes have a fruity or metallic smell. Bit awkward at dinner parties, but it’s actually a good sign.

These ketones cross the blood-brain barrier and fuel your brain directly. Your muscles and organs use them too. In fact, your heart actually prefers ketones over glucose as a fuel source.

The shift from glucose burning to fat burning takes several days. During this period, your body is essentially learning a new skill. It hasn’t had to produce significant ketones since, well, possibly never if you’ve spent your whole life eating three meals a day plus snacks. That learning period is why some people feel rough in the first week. Your body will catch up. It just needs time.

How to Get Into Ketosis

Getting into ketosis is straightforward. Not easy, mind you. But straightforward. There’s a difference.

1. Cut your carbs to 20 to 50g per day

This is the non negotiable bit. Most people reach ketosis somewhere around 20 to 30g of net carbs daily. Some can manage 50g and still produce ketones. Your personal threshold depends on your metabolism, activity level, and genetics.

At The Keto Collective, we recommend starting at 20g and seeing how you feel. You can always experiment upwards once you’re fat adapted.

2. Eat enough protein

Aim for roughly 1.2 to 2.0g of protein per kilogram of body weight. Too little and you risk losing muscle. Too much and… well, there’s a common myth I should address.

You’ve probably heard that excess protein “turns into sugar” and kicks you out of ketosis. This is one of the most persistent myths in the keto world and it drives me mad. Your body does convert some amino acids to glucose through a process called gluconeogenesis. But this process is demand driven, not supply driven. Your body makes the glucose it needs for cells that can’t use ketones (red blood cells, for example) regardless of how much protein you eat.

Eating a chicken breast is not going to ruin your ketosis. Eating 400g of protein with minimal fat might make things less efficient, but that’s an extreme nobody is accidentally stumbling into.

3. Increase healthy fats

On a ketogenic diet, around 70 to 80% of your calories come from fat. Avocados, olive oil, coconut oil, butter, cheese, fatty fish, nuts. These are your new best friends.

I remember when I first started keto and poured olive oil over everything. My husband thought I’d lost the plot. But once he saw the results, he was drowning his salads in it too.

4. Try intermittent fasting

Fasting depletes your glycogen stores faster, which means you reach ketosis sooner. A 16:8 pattern (eating within an 8 hour window) works well alongside keto. Many of my clients combine the two and find it speeds things along noticeably.

5. Move your body

Exercise burns through stored glycogen. Even a brisk walk or some light resistance training in the first few days can accelerate the switch into ketosis.

6. Test your levels

You can guess whether you’re in ketosis based on how you feel. Or you can actually know. I’d recommend knowing, at least in the beginning. Blood meters are the gold standard. Urine strips are cheaper and fine for confirming you’ve crossed the threshold.

RELATED: Stock up on the right foods with our guide to High Fat Keto Foods

How Long Does It Take to Get Into Ketosis?

Most people enter ketosis within 2 to 7 days of starting a ketogenic diet. I’ve seen clients get there in 36 hours with a combination of fasting and exercise. I’ve also seen it take a full 10 days for someone coming off a very high carb diet.

Your body has to burn through its glycogen stores before it starts producing ketones in meaningful quantities. Think of glycogen as your body’s glucose savings account. The more you’ve deposited (through weeks of pasta and bread), the longer it takes to empty.

What to expect day by day:

Day

What Happens

Days 1 to 2

Glycogen stores start depleting. You’ll wee more than usual. Initial water weight drops off.

Days 2 to 4

Blood sugar drops. Your liver begins producing ketones. Keto flu symptoms may appear. This is often the hardest stretch.

Days 4 to 7

Ketone production ramps up. Urine strips start showing positive. Energy can be a bit all over the place.

Weeks 2 to 4

Your body gets better at using ketones. Keto flu resolves. Energy steadies and often improves noticeably.

Weeks 4 to 12

Full fat adaptation. Your body can efficiently switch between fuel sources. This is the sweet spot.

Things that speed up the process:

• Fasting for 24 to 48 hours before starting

• Exercise (even gentle walking helps)

• Starting with 20g carbs rather than 50g

• Being younger and more metabolically healthy

• Lower pre existing glycogen stores

Things that slow it down:

• Coming from a very high carb diet

• Being sedentary

• Insulin resistance

• Hidden carbs sneaking in (sauces, dressings, “low carb” products that aren’t actually low carb)

• Age and metabolic history

One thing I notice with my clients: the people who struggle most in the first week are often the ones who were most addicted to carbs beforehand. If you’ve been living on cereal, sandwiches, and pasta for 20 years, your body is going to put up a fight. That’s normal. 

Push through it.

Signs and Symptoms of Ketosis

How do you know if you’re actually in ketosis? Your body gives you some fairly obvious signals.

Keto breath

Acetone is released through your breath when you’re producing ketones. It smells fruity or metallic, a bit like nail polish remover. My husband could always tell when I was deep in ketosis because he’d get a whiff and say “you’re doing that thing again.” Romantic, eh? The good news is it usually fades after a few weeks as your body gets more efficient at using ketones rather than excreting them.

Reduced appetite

This one catches people off guard. You wake up one morning and realise you’re… not hungry. At all. Ketones suppress ghrelin, your hunger hormone, and it’s one of the most powerful effects of ketosis. A pilot study on ketogenic diets and depression confirmed this objectively: participants reported the same level of hunger at week 10 as at the start of the study, despite eating significantly fewer calories. I’ve had clients tell me they forgot to eat lunch. On a standard diet, that would never happen.

Increased energy and mental sharpness

Once you’re past the adaptation phase, many people report feeling like someone’s turned the lights on. Clearer thinking. Steadier energy through the day without the 3pm crash. Your brain runs very efficiently on ketones.

Early fatigue and brain fog

Before the energy boost comes the slump. During the first 3 to 7 days, you might feel tired, foggy, and generally rubbish. This is your body figuring out how to make and use ketones efficiently. It passes.

Increased thirst and weeing

As glycogen depletes, it releases water. You’ll be running to the loo frequently in the first week. Drink plenty and keep your electrolytes up.

Digestive changes

Constipation is common because fibre intake often drops when you cut carbs. Make sure you’re eating plenty of above ground veg. Broccoli, spinach, courgettes, cauliflower. These are low carb and keep things moving.

Positive test results

The most reliable sign of all. A blood ketone reading above 0.5 mmol/L means you’re in nutritional ketosis. No guesswork required.

RELATED: Feeling rough? Read about Keto Flu: Symptoms and Prevention

Ketosis Numbers: Blood Ketone and Blood Sugar Levels

Numbers matter in ketosis. Not to make you obsessive, but to give you an objective picture of what’s happening inside your body.

Blood Ketone Levels (Beta Hydroxybutyrate)

Level

What It Means

Below 0.5 mmol/L

Not in ketosis

0.5 to 1.0 mmol/L

Light nutritional ketosis. Weight loss can happen here.

1.0 to 3.0 mmol/L

Optimal nutritional ketosis. The sweet spot for most health benefits.

3.0 to 5.0 mmol/L

Deep ketosis. No extra weight loss benefit. Sometimes used therapeutically for epilepsy or neurological conditions.

Above 5.0 mmol/L

Unusually high. Get medical advice if you don’t have a specific medical reason for these levels.

Above 10 mmol/L

Dangerous territory. Risk of ketoacidosis. Medical emergency for diabetics.

I want to be clear about something. Chasing higher ketone numbers does not mean faster fat loss. I’ve had clients obsess over getting their readings from 1.5 to 2.5 mmol/L thinking it would speed up weight loss. It doesn’t. Anything above 0.5 mmol/L means your body is burning fat for fuel. Higher numbers reflect ketone production, not fat burning efficiency.

Blood Sugar Levels for Ketosis

When you’re in nutritional ketosis, fasting blood sugar typically runs between:

Research confirms the inverse relationship between these two numbers. In controlled studies, blood glucose decreased by 19.97% (p=0.01) in ketogenic diet subjects, while blood ketone (BHB) concentration increased by 43.48% (p=0.0004), with a significant inverse correlation (Pearson’s r = -0.58, p<0.01). In plain English: as your ketones go up, your blood sugar comes down. They move in opposite directions, and the relationship is statistically robust.

Individual variation exists. Stress, poor sleep, and even intense exercise can temporarily raise blood glucose even when you’re solidly in ketosis. Don’t panic over a single reading. Look at trends over days and weeks.

If you have diabetes, work closely with your healthcare provider when monitoring these numbers. Medication adjustments are often needed.

Testing Methods Compared

Method

Measures

Accuracy

Cost

Best For

Urine strips

Acetoacetate

Lower accuracy. Becomes less reliable once fat-adapted.

£5 to £10 for 100 strips

Beginners confirming initial ketosis

Blood meter

BHB

Most accurate

£20 to £40 for device. £1 to £2 per strip.

Precise tracking and medical purposes

Breath analyser

Acetone

Moderate. Varies by device quality.

£50 to £150 one off purchase

Convenient long term monitoring without ongoing costs

My honest advice? Start with urine strips because they’re cheap and they’ll confirm you’ve crossed into ketosis. After a few weeks, switch to a blood meter if you want precision. 

The urine strips become less useful once you’re fat adapted because your body gets better at using ketones rather than excreting them, so the strips show lower readings even when you’re deeper in ketosis.

Keto vs Low Carb Diet: What’s the Difference?

I get this question weekly. Is keto the same as low carb? No. The keto diet is a specific type of low carb diet, but not all low carb diets produce ketosis.

Keto Diet

Low Carb Diet

Atkins Diet

Daily carbs

Under 20 to 50g

50 to 150g

Varies by phase (20g to 100g+)

Fat intake

Very high (70 to 80%)

Moderate to high

High

Protein

Moderate (about 20%)

Variable

Not restricted

Goal

Achieve and stay in ketosis

Reduce carbs for weight loss or health

Weight loss through phases

Ketosis

Yes, sustained

Usually not

Only in induction phase

The practical difference? On a ketogenic diet, you’re specifically trying to get your body producing ketones. The high fat, moderate protein, very low carb ratio is designed to flip that metabolic switch and keep it flipped.

On a low carb diet, you might eat 80 to 100g of carbs daily. That’s less than the average Brit’s 250 to 300g, and you’ll probably lose weight, but you won’t be in ketosis. Your body is still running primarily on glucose.

The Atkins diet starts with a strict induction phase that looks a lot like keto, but then gradually adds carbs back over subsequent phases. Most people exit ketosis as they progress through Atkins.

Which is better? Depends on your goals. If you want the specific metabolic benefits of ketone production, like enhanced mental clarity, appetite suppression, and potentially faster fat loss, then keto is the way. If you just want to eat fewer carbs and feel a bit better, a general low carb approach might suit you fine.

We actually have a full comparison of these approaches if you want the details: Keto vs Low Carb vs Atkins

Health Benefits and Risks of Ketosis

Health Benefits of Ketosis

The research on ketosis has grown massively over the last decade. Here’s what the science actually supports.

Weight loss and fat burning

This is the headline benefit and it’s well supported. A 2013 meta-analysis in the British Journal of Nutrition analysing 13 randomised controlled trials found that people on ketogenic diets lost significantly more weight than those on low-fat diets, even when calorie intake was similar between groups. More recently, a systematic review of very-low-calorie ketogenic diets (VLCKDs) showed a standardised mean body weight reduction of -5.63 (p=0.008) and a waist circumference reduction of -2.32 (p=0.04) compared to control diets. Ketones suppress hunger hormones, stabilise blood sugar, and your body becomes a very efficient fat burning machine. I’ve watched hundreds of people lose significant weight on keto at The Keto Collective. The ones who stick with it consistently see the best results.

Blood sugar control

By dramatically cutting carbs, you remove the thing that spikes blood sugar in the first place. A meta-analysis of ketogenic diet interventions for type 2 diabetes found a significant HbA1c reduction (standardised mean difference -0.38, p=0.0008) and triglyceride reduction (SMD -0.36) across studies lasting 3 months to 2 years. A landmark 2018 study published in Diabetes Therapy followed 262 type 2 diabetics on a supervised ketogenic diet for one year. 60% of participants reduced their HbA1c to below the diabetic threshold (<6.5%), with mean HbA1c dropping from 7.6% to 6.3% — a clinically significant 1.3% absolute reduction. Insulin resistance (HOMA-IR) decreased by 55% and the inflammation marker hsCRP dropped by 39%.

Reduced hunger and cravings

Ketones directly suppress ghrelin. This isn’t willpower. It’s biochemistry. Your brain receives fewer hunger signals when you’re in ketosis. I genuinely believe this is the most underrated benefit. Every diet works better when you’re not fighting constant hunger.

Stable energy

No more blood sugar rollercoasters. When you’re running on ketones, your energy stays remarkably steady from morning to night. That afternoon slump where you’d normally reach for a biscuit? Gone.

Neurological benefits

The keto diet was literally invented for this. A Cochrane systematic review (the highest level of medical evidence) confirmed that the ketogenic diet achieves >50% seizure reduction in children with drug-resistant epilepsy, making it a standard of care for refractory cases. 

Beyond epilepsy, emerging clinical studies show Parkinson’s patients experienced improvements in anxiety, mood, short-term memory, and verbal fluency on a ketogenic diet. Multiple sclerosis patients showed reduced expression of pro-inflammatory enzymes after 8 weeks or more. And migraine sufferers saw reductions in both frequency and severity of attacks. 

A pilot study on depression found significant improvements across three validated depression scales (PHQ-9, HRSD, and WHO-5), with participants reporting the same level of hunger at week 10 as at study start — meaning the diet didn’t make them miserable to stick with. The science is still developing across these conditions, but the early results are genuinely promising.

Improved blood lipids

The numbers here are compelling. In the Virta Health clinical trial, after one year on a supervised ketogenic diet, participants saw triglycerides drop by 24%, HDL (good) cholesterol rise by 18%, and white blood cell counts significantly reduce. Liver enzymes (ALT, AST, ALP) all declined significantly (p≤0.0001), suggesting improved liver health. 

LDL cholesterol is more complicated – it increased by approximately 10% on average, but here’s the nuance: apolipoprotein B (widely considered a more predictive cardiovascular risk marker than LDL alone) remained unchanged (p=0.37), and overall 10-year ASCVD risk scores actually improved. I’ll address the LDL question in more detail in the risks section.

Risks and Side Effects of Ketosis

I wouldn’t be much of a nutritional therapist if I glossed over the downsides. Ketosis has real side effects and isn’t right for everyone.

Short Term Side Effects

Keto flu

The first 1 to 2 weeks can be rough. Headaches, fatigue, nausea, dizziness, irritability. Your body is adapting to a completely new fuel source. The good news: adequate hydration and electrolytes (sodium, magnesium, potassium) dramatically reduce these symptoms. I tell all my new clients to salt their food generously and consider an electrolyte supplement in the first month.

Digestive issues

Constipation is the most common complaint I hear. It usually comes down to not eating enough fibre rich vegetables. Eat your greens. Broccoli, spinach, and avocado are low carb and keep your gut happy.

Keto breath

That fruity, metallic smell from acetone production. It can be a bit embarrassing. It typically fades within a few weeks. In the meantime, sugar free mints are your friend.

Muscle cramps

Electrolyte imbalances, particularly low magnesium and potassium, cause cramping. This is easily fixed with proper supplementation.

Longer Term Considerations

Nutrient gaps

Cutting out entire food groups means you might miss certain vitamins and minerals. This is why eating a varied keto diet with plenty of vegetables matters. A multivitamin isn’t a bad idea either.

Cholesterol response

This is the one that generates the most debate. Most people see their cholesterol profile improve on keto, with lower triglycerides and higher HDL. But approximately 18% of people on carbohydrate-restricted diets develop what researchers call the “Lean Mass Hyper-Responder” (LMHR) phenotype: LDL-C ≥0 mg/dL, HDL-C ≥80 mg/dL, and triglycerides ≤70 mg/dL. Some individuals experience LDL increases from ~100 mg/dL to 500–800 mg/dL — and intriguingly, the leaner you are, the greater the LDL rise tends to be. However, a landmark 2024 study published in JACC (the Journal of the American College of Cardiology) called the KETO Trial found that 80 LMHR individuals with mean LDL-C of 272 mg/dL showed no significant difference in coronary plaque burden compared to matched controls with LDL-C of just 123 mg/dL. 

No correlation was found between LDL-C level and total plaque score in the LMHR group. This is one study with a modest sample size, so it’s not the final word. But it does suggest the picture is more nuanced than “high LDL = high risk” in every context. If your LDL shoots up dramatically on keto, get proper medical advice from a doctor who understands the nuance, and don’t just ignore it.

Kidney considerations

If your kidneys are already compromised, a high fat, moderate protein diet needs careful management. Healthy kidneys cope fine. Damaged ones might not.

Gut bacteria changes 

A 2020 study published in Cell (one of the world’s most prestigious scientific journals) found that BHB (the primary ketone your body produces) directly inhibits the growth of Bifidobacteria in the gut. However, here’s where it gets interesting: this reduction was actually associated with decreased pro-inflammatory Th17 cells in intestinal and visceral fat tissue, suggesting it may be part of how keto reduces inflammation. 

More recent 2024 research found 79 metabolites significantly changed in post-ketogenic-diet fecal samples. The diet increased Akkermansia muciniphila (a bacterium linked to improved insulin sensitivity) and short-chain fatty acid-producing Lachnospiraceae. The practical takeaway? A novel ketogenic diet with added dietary fibre was shown to restore short-chain fatty acid levels and prevent liver steatosis (fatty liver). So eat your low-carb vegetables, include fermented foods like sauerkraut and natural yoghurt, and don’t treat keto as an excuse to eat nothing but meat and cheese.

Ketosis for Weight Loss

Let’s talk about the thing most people actually care about. How well does ketosis work for shedding fat?

Pretty well, if you do it properly.

Why ketosis promotes fat loss:

Your body is literally burning fat as its primary fuel. Both the fat you eat and the fat stored on your body. Metabolic chamber studies suggest that total daily energy expenditure may increase by approximately 400–600 kcal/day on a ketogenic diet compared to a high-carbohydrate diet, with significantly increased fat oxidation. (This figure is debated among researchers, but the directional finding — that keto increases energy expenditure — has been replicated.) When combined with a calorie deficit, the results can be impressive. In one clinical trial combining a ketogenic diet with an intragastric balloon, the KD group lost 19kg total versus 12kg in the low-calorie diet group — an additional 8kg versus 3kg beyond the device effect alone.

Ketones suppress hunger. This means you naturally eat less without feeling deprived. I’ve seen this with so many clients. They start keto expecting to be hungry all the time and within two weeks they’re saying “I can’t finish my meals.”

Stable blood sugar means fewer cravings. No more 4pm raids on the vending machine. No more “I need something sweet” after dinner.

With adequate protein, you preserve muscle mass while losing fat. This matters because muscle drives your metabolism. Lose muscle and your metabolic rate drops. Keep muscle and the fat keeps coming off.

Realistic expectations:

Week 1: You’ll lose 2 to 5kg. I know that sounds amazing but I need to be honest with you. Most of this is water. When glycogen depletes, it releases stored water. It’s still motivating to see the scale move, but don’t expect that rate to continue.

Weeks 2 to 4: Fat loss begins properly. Expect 0.5 to 1kg per week. This is real, sustainable fat loss.

Months 2 to 6: Continued fat loss if you’re maintaining a calorie deficit. The rate may slow as you get lighter. This is normal, not a sign that keto has “stopped working.”

I always tell people: don’t compare your week 8 results to someone else’s week 1 results. Everyone loses weight at different rates depending on their starting point, age, activity level, and metabolic health.

RELATED: More detail in our guide to Losing Weight with the Keto Diet

RELATED: Keto Weight Loss Timeline

Considering Ketosis with Medical Conditions

Ketosis and Diabetes

The relationship between ketosis and diabetes is something I feel strongly about as a nutritional therapist. The research is compelling, but the approach needs care.

Type 2 Diabetes

Multiple studies show the ketogenic diet can help people with type 2 diabetes improve blood sugar control, reduce HbA1c, decrease insulin resistance, and potentially reduce or eliminate certain medications.

A landmark study by Virta Health (2018) followed 262 type 2 diabetics on a supervised ketogenic diet for one year. 60% achieved HbA1c levels below the diabetic threshold. 94% of insulin users reduced or eliminated their insulin. These are remarkable numbers — but the long-term data is even more interesting.

At 2 years, 38% had achieved full diabetes reversal (HbA1c <6.5% without medication except metformin), 91% of insulin users had reduced or eliminated insulin, and 67% had discontinued all diabetes-specific prescriptions. Study retention was 74% at 2 years — unusually high for a dietary intervention.

At 5 years (data published October 2024), 61.3% of completers sustained ≥5% weight loss and 39.5% maintained ≥10% weight loss. By 3.5 years, 71% of all diabetes medications (other than metformin) had been discontinued, and sulfonylureas were entirely eliminated from the treatment group.

The cost implications are striking too. The TOWARD pilot study (a VA health system collaboration with Virta) found that 96 medications were deprescribed among just 50 participants over one year, with only 8 new medications started — representing estimated savings of ~£1,400 per patient annually versus ~£10,600 per year for GLP-1 receptor agonists like semaglutide (Ozempic/Wegovy).

But and this is a big but. If you have type 2 diabetes and take medication, you cannot just start a keto diet without talking to your doctor. Cutting carbs dramatically while still taking blood sugar lowering medication can cause dangerous hypoglycaemia. Your doses will almost certainly need adjusting. This needs medical supervision.

Type 1 Diabetes

People with type 1 diabetes should only attempt ketosis under strict medical supervision. Without adequate insulin, there is a serious risk of diabetic ketoacidosis, which is a medical emergency. I won’t go into more detail here because this is firmly in the territory of specialist medical care, not general nutrition advice.

The metabolic syndrome concepts closely related to diabetes are covered in more detail in our dedicated guide.

RELATED: Our full guide on Keto and Diabetes

Ketosis vs Ketoacidosis

This is the confusion that won’t die. Every time ketosis comes up in conversation, someone says “isn’t that dangerous?” They’re confusing nutritional ketosis with diabetic ketoacidosis. These are completely different conditions.

Nutritional Ketosis

Diabetic Ketoacidosis

Ketone levels

0.5 to 3.0 mmol/L

Over 10 mmol/L

Blood sugar

Normal or low

Very high (often over 250 mg/dL)

Blood pH

Normal

Acidic (below 7.3)

Who it affects

Anyone on a low carb diet

Primarily people with type 1 diabetes

Is it dangerous?

No. Natural metabolic state.

Yes. Medical emergency.

In a healthy person, nutritional ketosis cannot cause ketoacidosis. Your body has a built in safety mechanism: when ketone levels rise, the pancreas releases a small amount of insulin that prevents dangerous accumulation. This feedback loop keeps ketones within a safe range.

In type 1 diabetes, this mechanism is broken because the pancreas doesn’t produce insulin. Without insulin to act as a brake, ketones can accumulate to lethal levels. That’s ketoacidosis.

If you’re a healthy adult with a functioning pancreas, you do not need to worry about ketoacidosis from a ketogenic diet. Full stop.

How to Stay in Ketosis

Getting into ketosis is one thing. Staying there requires some ongoing attention.

Keep carbs under your personal threshold

For most people that’s 20 to 30g net carbs daily. Hidden carbs are the biggest saboteur. Sauces, dressings, “low carb” wraps, and even some medications contain carbs that add up quietly.

Test periodically

Especially when trying new foods. I had a client who thought she was in ketosis for months. Turned out her daily “sugar free” yoghurt was knocking her out every morning. A quick blood test would have caught that immediately.

Plan your snacks

Being caught hungry without keto options is how most people fall off the wagon. Keep something reliable in your bag. Our Keto Bars have 2.2 to 2.4g net carbs and are made from almonds, sunflower seeds, and chicory root fibre. No artificial sweeteners, no maltitol, no sugar alcohols. I carry one in my handbag at all times. If you fancy something sweeter, the Keto Cookies are 1.5g net carbs each, made with British grass fed butter and real ingredients.

Stay consistent

One high carb meal can knock you out of ketosis for 1 to 3 days. If you have a slip up, don’t spiral. Just get back on track with your next meal.

Watch the alcohol

A glass of dry wine or a neat spirit is usually fine. But your liver has to process the alcohol before it can go back to producing ketones. Too much booze and your ketosis stalls. We’ve got a full guide on Alcohol on Keto if you want the details.

How Long Should You Stay in Ketosis?

Here’s something most keto content won’t tell you: until recently, the longest rigorous studies on ketosis were around 2 years. That changed in 2024, when Virta Health published 5-year clinical outcomes — one of the longest ketogenic diet datasets we have. Their retention rates were 90.8% at 11 weeks, 83% at 1 year, and 74% at 2 years — remarkably high for any dietary intervention, attributed to continuous remote care and monitoring.

Does that mean we have all the answers on long-term keto? Not yet. But the evidence base is getting stronger. And the safety data from these extended trials has been reassuring.

Some people thrive on keto for years. They feel brilliant, their blood work looks great, and they have no desire to change. Others find that strict keto becomes unsustainable after 6 to 12 months. Both are valid responses.

After reaching your initial goals, you might consider:

• Staying on strict keto if it’s working and feels sustainable

• Trying cyclical keto (5 days strict, 2 days slightly higher carb)

• Shifting to moderate low carb (50 to 100g carbs daily)

• Using keto periodically for metabolic resets a few times per year

If you’re staying in ketosis long term, get regular blood work. Lipids, liver function, kidney function, thyroid. Not because something will definitely go wrong, but because monitoring is sensible when you’re eating in a way that’s significantly different from the standard diet.

Why Ketosis Affects Everyone Differently

Wondering why your mate lost 2 stone in a month while you’re struggling to shift half a stone? I hear this all the time. Ketosis is not one size fits all.

Genetics play a big role. The APOE4 gene variant, carried by about 25% of the population, can cause LDL cholesterol to spike dramatically on high-fat diets. Research has also identified the LMHR phenotype, where the magnitude of LDL increase is inversely associated with BMI — meaning the leaner and more metabolically healthy you are, the greater the LDL rise. This is the opposite of what most people expect. Some individuals see LDL jump from ~100 mg/dL to 500–1800 mg/dL, levels comparable to genetic familial hypercholesterolemia. Other genetic profiles see cholesterol improve. This is why blanket statements about keto and heart health are usually wrong in one direction or another.

Your metabolic history matters. Starting keto at 25 after being relatively healthy is a very different proposition to starting at 55 after decades of yo yo dieting and insulin resistance. Your body’s ability to switch fuel sources gets less efficient with age and metabolic damage.

Gut bacteria affect adaptation. Your baseline microbiome influences how smoothly you adapt. People with diverse, healthy gut bacteria going in tend to have an easier time.

Activity level changes the equation. Someone doing CrossFit five times a week needs a different approach to someone who walks 30 minutes daily. High intensity athletes might do better with targeted keto (adding carbs around workouts) or cyclical approaches.

What this means for you: monitor YOUR response, not someone else’s. If you can, get baseline blood work done before starting: full lipid panel, fasting glucose and insulin, inflammatory markers. Then retest at 3 and 6 months. That gives you actual data instead of guesswork.

What’s New in Ketosis Research (2024 to 2025)

The Cholesterol Response Is Individual

The biggest headline from 2024 was the KETO Trial, published in JACC (Journal of the American College of Cardiology) in August 2024. Researchers assessed 80 Lean Mass Hyper-Responder individuals with a mean LDL-C of 272±91 mg/dL (more than double the “normal” range) who had been on ketogenic diets for an average of 4.7 years. Using coronary CT angiography, they found no significant difference in coronary plaque burden compared to matched controls with LDL-C of just 123±38 mg/dL. Even more striking: there was no correlation whatsoever between LDL-C level and total plaque score within the LMHR group. The mean BMI in the LMHR group was just 22.5 kg/m² versus 25.8 kg/m² in controls — reinforcing the inverse relationship between leanness and LDL elevation on keto. This doesn’t mean sky-high LDL is harmless. But it does challenge the assumption that elevated LDL always carries the same risk regardless of metabolic context.

Gut Bacteria Research Is Evolving

The gut microbiome story on keto is more nuanced than “keto kills good bacteria.” Yes, a landmark Cell study confirmed that BHB directly inhibits certain Bifidobacteria species. But 2024 research found the ketogenic diet also increased Akkermansia muciniphila (associated with improved insulin sensitivity and negatively correlated with BMI) and Lachnospiraceae (short-chain fatty acid producers). 79 metabolites were found to be significantly altered in post-KD fecal samples. The practical takeaway: the gut changes are both positive and negative, and the negative effects can be mitigated. Studies show a ketogenic diet supplemented with added fibre restored cecal short-chain fatty acid levels and prevented liver steatosis. Eat your vegetables, include fermented foods, and consider a fibre supplement if your vegetable intake is low.

Personalised Nutrition Is Where Things Are Heading

Your genes, gut bacteria, age, hormonal profile, and activity level all influence how your body responds to ketosis. The future of nutrition is personalised, not prescriptive. The best approach is finding what works for YOUR body through testing, monitoring, and honest self assessment.

5-Year Clinical Data Now Available

One of the biggest criticisms of ketogenic diets has always been “where’s the long-term data?” That gap is closing. Virta Health published 5-year outcomes in October 2024, making it one of the longest-running ketogenic diet clinical datasets. Among completers, 61.3% sustained ≥5% weight loss at 5 years and 39.5% maintained ≥10% weight loss. Diabetes remission was achieved by 20% at 2 years, with 12.5% maintaining full remission at 5 years. Liver enzymes continued to improve, and the overall safety profile remained favourable. This won’t silence every critic, but it significantly strengthens the case for keto as a sustainable, long-term dietary approach when properly supported.

Finally On… What is Ketosis?

I’ve worked with hundreds of people on ketogenic diets through The Keto Collective. I’ve seen the results first hand, both the incredible successes and the occasional struggles.

Ketosis works. The science supports it. The clinical evidence for weight loss, blood sugar control, and neurological benefits is strong and getting stronger.

But it’s not magic. It still requires eating real food, managing your portions, staying consistent, and listening to your body. And it’s not for everyone. Some people do brilliantly on a more moderate low carb approach without ever needing to chase ketone numbers.

If you’re considering trying ketosis, start properly. Read up. Get your cupboards sorted. Have a plan for the first difficult week. And if you want convenient keto snacks that won’t compromise your progress, we use real ingredients with no artificial nonsense. Because staying in ketosis shouldn’t mean going hungry or eating rubbish.

How can I tell if I’m in ketosis?

Common signs include reduced appetite, increased energy, acetone on your breath (fruity or metallic smell), and rapid weight loss in the first week. The most reliable method is testing with a blood ketone meter. A reading above 0.5 mmol/L confirms nutritional ketosis.

Is ketosis dangerous?

For most healthy adults, nutritional ketosis is safe. It’s a natural metabolic state that your body is designed to enter. People with type 1 diabetes, kidney disease, liver disease, or who are pregnant should get medical advice before attempting ketosis. Ketosis is completely different from dangerous ketoacidosis.

Is keto the same as low carb?

No. Keto is a specific type of low carb diet that aims to induce ketosis by restricting carbs to under 20 to 50g daily. Low carb diets may include 50 to 150g carbs and don’t typically produce ketosis. All keto diets are low carb, but not all low carb diets are keto.

What is the blood sugar level for ketosis?

During ketosis, fasting blood glucose typically runs between 70 to 90 mg/dL (3.9 to 5.0 mmol/L). This is lower than on a standard diet because your body is primarily using ketones rather than glucose for fuel.

Does ketosis burn belly fat?

Ketosis promotes overall fat burning, including visceral fat around the abdomen. You cannot spot reduce fat from specific areas. Consistent ketosis combined with a calorie deficit leads to fat loss across the body, and abdominal fat often responds well to reduced carbohydrate intake and lower insulin levels.

Can I do keto if I have type 2 diabetes?

How much weight can I lose in ketosis?

Results vary. The first week typically shows 2 to 5kg loss, mostly water from glycogen depletion. After that, typical fat loss is 0.5 to 1kg per week with a calorie deficit. Individual results depend on starting weight, adherence, activity level, and metabolic health.

How long does it take to get into ketosis?

Most people enter ketosis within 2 to 7 days of restricting carbs to under 20 to 50g daily. Factors like your previous diet, activity level, and metabolic health affect the timeline. Combining carb restriction with fasting or exercise can speed up the process.

Can you stay in ketosis long term?

Some people maintain ketosis successfully for years. Others do better cycling in and out or shifting to moderate low carb after reaching their goals. Long term research beyond 2 years is limited, so regular health monitoring with blood work is recommended for anyone staying in ketosis indefinitely.

SUZIE WALKER 

Keto Collective Co-Founder & Naturopathic Nutritionist dipNT.CNM 

Suzie has researched and reviewed the many health benefits of low-carb living. She co-founded The Keto Collective, a company that aims to make it easier to find whole food, great tasting, keto alternatives to their everyday favourites.

Read more about Suzie Walker