How many carbohydrates can I eat and stay in ketosis?

When following a ketogenic diet, it’s important to restrict your carbohydrate intake sufficiently to induce a metabolic state called ketosis. In ketosis, your body switches from using carbohydrates as its primary fuel source to using fats and ketones instead. This has many potential benefits related to weight loss, blood sugar control, heart health, and more. But how low do you need to go with your carb intake to stay in ketosis? Let’s take a look at the evidence.

What is ketosis?

Ketosis occurs when your body doesn’t have enough carbohydrates available to burn for energy. Instead, it begins breaking down stored fat into molecules called ketone bodies, which can be used as fuel by many tissues in your body, including your brain. Some of the most common ketones produced during ketosis are acetone, acetoacetate and beta-hydroxybutyrate (BHB). As ketone levels rise in your bloodstream, your body enters a state of ketosis. This is characterized by higher-than-normal levels of ketones in your blood or urine.

When you restrict carbs to very low levels, your body ramps up fat burning and ketone production. Blood ketone levels increase dramatically, often reaching levels of 1–5 mmol/L on low-carb diets compared to a normal range of about 0.1–0.3 mmol/L for non-ketogenic diets. Achieving and sustaining this metabolic state of elevated blood ketones provides most of the benefits associated with ketogenic diets.

How many carbs per day to stay in ketosis?

There isn’t a one-size-fits-all answer here, as the amount of carbs required to maintain ketosis varies between individuals. However, most people will need to keep their daily carb intake to somewhere between 30–50 grams of net carbs per day.

Net carbs refer to the grams of total carbohydrates in a food, minus grams of fiber and sugar alcohols it contains. Because fiber and certain sugar alcohols don’t raise blood sugar or insulin levels, they don’t count toward your daily carb limit on a keto diet.

Studies show that consuming around 30–50 net grams of carbs per day is typically enough to maintain ketosis for most people:

  • One study in 17 men with obesity found that eating 20–30 grams of net carbs per day significantly increased blood ketone levels compared to eating 50–75 grams per day.
  • Another study in adults with obesity showed that consuming 25 grams of net carbs per day led to greater weight loss and ketone levels compared to consuming 50 grams per day.
  • An analysis of several studies suggests that consuming no more than 50 grams of net carbs per day typically results in clinically significant levels of ketosis in most people.

However, some individuals — especially athletes, women, and those with metabolic disorders — may require lower carb intakes, such as 20–30 net grams per day to achieve adequate ketosis. Higher carb intakes of up to 100 grams per day may work for maintaining ketosis in some cases as well.

Factors influencing carb needs for ketosis

Your individual carb requirement for ketosis depends on several factors:

Insulin sensitivity

Insulin plays a key role in regulating blood sugar levels and ketogenesis. People who are more insulin resistant tend to require lower carb intakes to reach ketosis.

Metabolism

Your metabolic rate influences ketosis. Those with a higher metabolism may be able to eat more carbs while remaining in ketosis.

Activity levels

If you exercise regularly, especially at higher intensities, you may be able to consume more carbs while staying in ketosis. Active individuals often report consuming 50–100 grams of carbs per day on a ketogenic diet.

Body size

In general, the larger you are, the more carbs you can consume and remain in ketosis. Smaller people may need to eat closer to the lower end of the range.

Personal tolerance

Due to biochemical individuality, some people report remaining in ketosis at carb intakes well over 50 grams per day. Others need to eat closer to 20–30 grams to maintain ketosis.

Foods to eat on a keto diet

Here are some of the best low carb foods to eat on a ketogenic diet:

  • Meat: Beef, chicken, pork, lamb, etc.
  • Fish: Salmon, trout, tuna, mackerel, etc.
  • Eggs
  • Butter and cream
  • Cheese
  • Nuts and seeds
  • Healthy oils like olive oil and avocado oil
  • Low carb vegetables: Leafy greens, broccoli, cauliflower, zucchini, peppers, etc.
  • Berries in moderation
  • Avocados
  • Natural and zero-calorie sweeteners
  • Coffee, tea and water

When grocery shopping and meal planning for keto, stick to the whole, unprocessed food groups listed above as much as possible. These provide healthy fats, protein and carbs while avoiding processed and sugary foods.

Foods to avoid on a keto diet

Here are the main foods and ingredients to limit or avoid on keto:

  • Grains: Wheat, rice, oats, corn, barley, millet, etc.
  • Starchy vegetables: Potatoes, sweet potatoes, peas, winter squash, etc.
  • Fruit: Apples, bananas, grapes, pineapple, mangoes, etc.
  • Beans and legumes: Chickpeas, kidney beans, lentils, peanuts, etc.
  • High carb sauces and condiments: Barbecue sauce, sweet chili sauce, ketchup, etc.
  • Sweetened beverages: Soda, fruit juice, sports drinks, etc.
  • Sugar-heavy desserts: Cakes, cookies, candy, ice cream, etc.
  • Processed low fat foods: Often high in carbs and added sugars
  • Alcohol: Some options like wine and spirits in moderation

Reading nutrition labels is an easy way to steer clear of foods that aren’t keto-friendly. Avoid products with more than 5 grams of net carbs per serving.

Ketosis testing

There are a few ways to test your state of ketosis when starting a low carb or keto diet:

Check ketones in urine

Ketone urine strips are a simple way to test for the presence of ketones. However, they only show excess ketones not being used by your body.

Once keto-adapted, many people no longer show high ketones in urine despite being in ketosis. Therefore, urine testing isn’t recommended for long-term keto dieters.

Measure blood ketones

You can use a specialized meter to prick your finger and measure blood ketone levels. This provides a more accurate and reliable assessment of your state of ketosis.

Optimal ketone levels for health range from 0.5 to 3.0 mmol/L on most blood ketone meters.

Try a breath analyzer

A breath analyzer device allows you to blow into it and measure your ketone levels via your breath. This is another easy, non-invasive way to test ketones.

Signs you’re in ketosis

Here are some signs and symptoms indicating you’ve achieved ketosis:

  • Bad breath. A slightly fruity or metallic taste in the mouth.
  • Increased thirst and frequency of urination. Ketosis causes a diuretic effect.
  • Fatigue and weaker exercise performance for the first 1-2 weeks while adapting to keto. This resolves over time.
  • Digestive issues like constipation may occur.
  • Decreased appetite and carb cravings as your body adapts to burning fat instead.
  • Rapid weight loss in the first week due to fluid losses. Weight loss stabilizes after this.
  • A possible rash, dry skin or itchiness as ketosis begins.

These symptoms often resolve within 1-2 weeks as your body adapts to being in ketosis. If symptoms persist past the initial adaptation phase, try tweaking your diet to reduce carbs further or increase calories temporarily.

Health benefits of ketosis

Some health benefits associated with being in a state of nutritional ketosis include:

Weight loss

Ketosis suppresses hunger and carb cravings, making it easier to consume fewer calories without feeling hungry or deprived. Restricting carb intake also reduces insulin levels, allowing faster weight loss.

Reduced blood sugar and insulin levels

Consuming very low carb diets can help manage insulin resistance, metabolic syndrome, PCOS and type 2 diabetes.

Improved heart health

Ketosis has been linked to lower cardiovascular disease risk markers, including improved triglycerides, HDL cholesterol and inflammatory markers.

Increased mental focus

Many people report improved focus, concentration and mental clarity in ketosis. However, a small percentage may experience a mild “brain fog” for up to 1 month while adapting.

Seizure reduction

The ketogenic diet originated as a way to reduce seizures in epilepsy. It continues to be highly effective for this purpose.

Increased energy and physical endurance

After adapting to ketosis, many people report surges in sustained energy levels and stamina during physical activity. However, high intensity, explosive exercise performance may decrease temporarily.

Potential side effects of ketosis

Ketosis is generally safe for most people. However, there are some potential side effects to be aware of:

  • Keto flu: Some people get headaches, brain fog, poor energy, nausea, cramps or other symptoms when transitioning to keto. This resolves within a few days to weeks.
  • Digestive issues: Constipation, diarrhea and other GI issues may occur. Staying hydrated and eating more fiber can help.
  • Bad breath: A very low carb intake causes a fruity or metallic mouth odor. Drinking more water and chewing gum or mints can mask it.
  • Leg cramps: Some people report leg cramps. Increasing mineral intake helps for most people.
  • Lightheadedness: Low blood pressure and dizziness can occur. Check with your doctor if concerning and increase carbohydrates and calories.
  • Kidney stones: There is some concern about kidney stone risk on the ketogenic diet. Make sure to drink plenty of fluids.
  • Nutrient deficiencies: The diet is restrictive, so consulting a health professional can help you avoid deficiencies in certain micronutrients.

Most of these issues can be avoided by eating a nutrient-dense, well-balanced keto diet and supplementing where there are concerns.

A Sample Ketogenic Meal Plan

Here is a one day sample menu that comes out to around 30-50 grams of net carbs to get an idea of what a ketogenic diet looks like:

Breakfast:

  • 3 eggs fried in butter or olive oil with cheese, avocado and sliced tomato
  • Bulletproof coffee made with butter and MCT oil

Lunch:

  • Bunless burger topped with cheddar cheese, mushrooms and mixed greens salad

Dinner:

  • Grilled salmon served with boiled broccoli and side salad with ranch dressing

Snacks:

  • A handful of almonds
  • Small celery sticks with nut butter
  • Berries with whipped cream
  • 90% dark chocolate square

Tips for starting a ketogenic diet

Here are some tips for getting started with a keto diet to help ensure success:

  • Cut carbohydrates to 20-50 grams per day for 1-2 weeks, then adjust as needed to maintain ketosis.
  • Focus on getting the majority of your carbs from low carb vegetables and a moderate amount of berries.
  • Include 3-5 servings of healthy fats from foods like fatty fish, avocado, olive oil, nuts and seeds.
  • Meet your protein needs with meat, poultry, fish, eggs and dairy products.
  • Drink plenty of water and mineral-rich broth if you experience flu-like symptoms when starting keto.
  • Supplement with electrolytes from a sports drink or bouillon cube to prevent muscle cramps and headaches.
  • Consider taking MCT oil and exogenous ketones to boost ketone levels.
  • Test your breath, blood or urine periodically to ensure you stay in ketosis.
  • Allow 1-3 months for your body to fully adapt to burning fat and ketones for fuel.

Frequently Asked Questions

Is ketosis safe?

Ketosis is generally safe for most healthy people. However, people with certain conditions like liver or kidney disease, diabetes or metabolic disorders should consult a doctor first.

How long does it take to reach ketosis?

It typically takes 2-4 days of restricting carbs to under 50 grams per day to reach ketosis. Some reach it faster, especially with fasting, exercise or low carb diets.

Do calories matter on keto?

Yes. You’ll likely lose weight rapidly in the first week due to fluid losses. After this, calories still matter for fat loss. Reduce intake or increase physical activity to break through plateaus.

Can you gain weight on keto?

It’s unlikely given unrestricted calories. However, it’s possible to regain weight by eating excessive calories from fat and protein sources.

Can I drink alcohol in ketosis?

Yes, but alcoholic beverages can affect ketosis. Spirits like vodka and whiskey have minimal carbs and don’t need to be avoided. Wine should be limited.

Conclusion

In summary, a carbohydrate intake of 20-50 grams per day will induce ketosis for most people. However, some individuals can go up to 50-100 grams per day and remain in ketosis. Testing your blood, breath or urine ketones can help you find your carb sweet spot to sustain a state of ketosis for health benefits like weight loss, mental clarity, disease prevention and more.

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