When following a ketogenic diet, the goal is to get your body into a metabolic state known as ketosis. This is achieved by severely restricting carbohydrate intake, typically to less than 50 grams per day. This forces your body to switch from using glucose as its main source of fuel to using ketones, which are produced by burning fat.
Many people worry that eating too many carbs in a day can kick them out of ketosis. But how many carbs does it really take to get knocked out of ketosis? Can one day of higher carb intake be enough to undo all your hard work? Let’s take a closer look at how carbs impact ketosis.
How Many Carbs Per Day for Ketosis?
To get into ketosis initially, it is recommended to keep carbs to around 20-50 grams per day. The exact amount can vary between individuals. Some may need to go as low as 20 grams for ketosis, while others can get away with up to 50 grams.
Once in ketosis, most people will remain there as long as carbs are kept to around 50 grams or less per day. Consuming more than this amount consistently can jeopardize ketosis. However, an occasional higher carb day may not be enough to reverse ketosis, depending on the individual.
Here are some general carbohydrate guidelines for ketogenic diets:
- To induce ketosis: 20-50 grams per day
- To maintain ketosis: Less than 50 grams per day
- To reverse ketosis: More than 50-100 grams per day consistently
Again, exact thresholds vary between people. The only way to know your personal carb tolerance is through self-experimentation using blood or breath ketone testing.
Why Do Carbs Reverse Ketosis?
To understand why carbs can reverse ketosis, it helps to understand what ketosis is.
Ketosis occurs when the body shifts from relying primarily on glucose (sugar) for energy to relying on fat-derived ketones. This metabolic shift happens when carbohydrate restriction lowers insulin levels. Insulin is the hormone that allows glucose to enter cells for energy.
When carbs are restricted to below 50 grams per day, the body responds by breaking down fat into fatty acids and ketones. Ketones can be used by the brain and body for fuel in the absence of glucose.
As soon as more carbs are eaten again, the body preferentially uses glucose for energy instead of ketones. Insulin levels rise, and ketogenesis (ketone production) slows down. If carb intake remains high, with enough glucose available, ketone levels will plummet and the body will no longer be in nutritional ketosis.
This is because the body prefers to use glucose (from carbs) for energy when it is available. It takes metabolic flexibility and adaptation to become efficient at burning ketones from fat when glucose is low. An influx of dietary carbs can rapidly reverse these ketone-burning adaptations.
How Many Extra Carbs Kicks You Out?
There is no universal threshold for the amount of carbs that will definitely kick someone out of ketosis. It really depends on the individual. Some people can consume 100-150 grams of carbs per day and remain in light nutritional ketosis. Others may get kicked out by just 50-60 grams of carbs.
Factors that affect carb tolerance for ketosis include:
- Metabolic health and flexibility
- Physical activity levels
- Degree of keto-adaptation
- Insulin sensitivity
As a general rule, consuming 100-150 grams or more of carbs per day is likely to reverse ketosis in most people. However, some may be knocked out by as little as 50 grams of carbs.
The only way know your personal carb threshold is to slowly increase carbs while tracking ketones with a blood or breath meter.
Typical Effects of Extra Carbs on Ketosis:
- 50 grams: May not affect ketosis for highly active or keto-adapted individuals.
- 75-100 grams: Likely to notice a moderate drop in ketone levels.
- 100-150 grams: Ketone levels will significantly drop, but some ketosis may remain.
- 150+ grams: Most people will be kicked completely out of ketosis.
Again, effects will vary based on the individual. The more adapted you are to keto, the more your carb tolerance may increase. But for most people new to keto, sticking to under 50 grams daily is a safe bet.
Can One Higher Carb Day Kick You Out?
In most cases, a single day of higher carb intake is unlikely to reverse ketosis completely. However, it may cause a temporary drop in ketone levels.
Some effects of one high carb day may include:
- Lower ketone readings the next day or two after the spike in carbs. Blood BHB may drop from 1-3 mmol/L down to 0.5-1 mmol/L the day after extra carbs.
- It may take a couple days to recover back into optimal ketosis above 1.5 mmol/L blood BHB.
- Performance in high-intensity exercise may decline temporarily as the body readapts to using ketones again.
- Craving for carbs and hunger levels may increase.
But while one day of high carb eating may not totally reverse ketosis, it’s best to get right back into keto the next day. Sustained higher carb intake, even if spread out over multiple days, runs the risk of knocking you out of ketosis eventually.
Carb Tolerance While Keto Adapted
The longer someone follows the ketogenic diet, often the more carbs they can tolerate while still staying in ketosis. This is because metabolic flexibility is improved, allowing the body to switch back to burning ketones more efficiently after a carb load.
Well keto-adapted individuals may be able to consume 100-150 grams of carbs 1-2 times per week without losing ketosis. However, this tolerance depends on many factors, so your mileage may vary.
How to Get Back into Ketosis Quickly
The good news is that even if you get knocked out of ketosis, it is fairly quick and easy to get back in. Here are some tips:
- Restrict carbs again: Get net carbs below 20-50 grams per day for 1-3 days.
- Exercise: Intense exercise can help burn through glycogen to accelerate ketosis.
- Reduce protein intake: Lowering protein to 0.8 – 1.0 grams per pound of lean mass may help.
- Fasting: Going 12-16 hours without eating can induce ketosis faster.
- MCT Oil: Consuming medium chain triglycerides provides ketone bodies directly.
- Exogenous ketones: Ketone supplements like salts and esters raise ketone levels.
Using these strategies, most people can get back into nutritional ketosis within 2-4 days after having extra carbs. Keep carb intake minimal and test ketones to confirm you’re back.
Ways to Test If You’re In Ketosis
Here are some ways to test if you’re actually in ketosis:
- Blood ketone meter: Measures blood BHB levels. Goal is 0.5 – 3.0 mmol/L.
- Breath ketone meter: Measures acetone on breath. Goal is 40-160 ppm.
- Urine strips: Change color based on ketones. Less reliable for nutritional ketosis.
- Symptoms: Signs like reduced appetite or “keto breath.” Unreliable.
Using a blood or breath ketone meter provides the most accurate method to know your real-time ketone levels and confirm you’re in ketosis.
Long-Term Effects of Carb Loading
While an occasional carb load may not kick you out of ketosis permanently, regularly going extremely high carb can stall fat loss and damage metabolic health over time.
Here are some potential long-term effects of frequently carb loading on a ketogenic diet:
- May prevent keto-adaptation from fully developing
- Can stall weight and fat loss
- Greater fluctuations in energy, cravings and hunger
- Insulin resistance may develop
- Increased risk for diabetes and obesity
- Cardiovascular health may decline
On the other hand, cyclical and targeted ketogenic diets can incorporate strategic carb refeeds while still maintaining many benefits of ketosis. This involves sticking to keto most days, with a timed carb load once or twice per week.
But regularly going way overboard on carbs can undermine the results you’re trying to achieve. Those following a ketogenic diet for therapeutic reasons like epilepsy may need strict ketosis and should be more cautious.
Food Choices to Stay in Ketosis
Focus on these low-carb, high-fat foods to maximize ketone levels:
- Meat: Beef, chicken, pork, lamb, etc.
- Fish: Salmon, tuna, trout, mackerel, etc.
- Eggs
- Non-starchy vegetables: Greens, peppers, onions, etc.
- High-fat dairy: Butter, hard cheese, heavy cream
- Nuts and seeds
- Avocado and oils: Olive oil, coconut oil, MCT oil
- Berries in moderation
Avoid going overboard on the following higher-carb foods:
- Grains: Wheat, rice, pasta, bread, etc.
- Beans and legumes
- Root vegetables: Potatoes, sweet potatoes, carrots
- Fruits: Particularly very sweet fruits like bananas
- Processed carbs and sugars
Stick to nutritious, low-carb foods most of the time. Save any high carb treats for occasional intake.
Summary
To summarize, here are the key points on carbs kicking you out of ketosis:
- It typically takes at least 50 grams of carbs to reverse ketosis depending on the individual.
- Consuming over 100-150 grams of carbs almost guarantees leaving ketosis for most people.
- A single day of high carbs probably won’t kick you entirely out of ketosis.
- Ketone levels will drop, but ketosis will resume within a couple days if carbs are restricted again.
- Frequently going very high carb can prevent keto adaptation and stall progress.
- The longest someone has been in ketosis, often the more carbs they can handle in occasional refeeds.
Ketosis is a metabolic state that responds quickly to changes in carb intake. Be mindful of your carbohydrate intake, test your ketone levels, and get back into keto right away after any cheats or refeeds.
