Your body depends on carbohydrates for energy (in the form of glucose) — quite simply, you couldn’t survive without them. Still, there are plenty of reasons you might want to limit your carbohydrate intake, such as losing weight or feeling less fatigued after lunch.
However, low-carb diets like the ketogenic diet can temporarily disrupt the body's glucose and insulin response [1].
Carbohydrate intolerance, or a more sensitive response to eating carbs, can occur after following a ketogenic diet as your body becomes more efficient at using fat as a fuel source and less efficient at using carbohydrates. A low-carb diet like keto may cause temporary insulin resistance and carbohydrate sensitivity, but it does not necessarily make it "dangerous" or a reason to avoid it.
Your body on a keto or low-carb diet
The ketogenic diet, commonly known as "keto," is a low-carbohydrate, high-fat diet that switches your body’s main fuel source away from carbohydrates to mainly utilize fat [2].
When carbs are eliminated from the diet, the body enters a metabolic state called ketosis, where it burns stored fat for energy. This can lead to weight loss, improved insulin sensitivity, and other health benefits, but it also has some potential downsides.
Many people who try the ketogenic diet find it works best for their body and lifestyle and will continue the diet permanently. However, others like to switch back from keto once they achieve a specific weight or health goal.
What happens to glucose levels after transitioning out of keto
Those wearing a continuous glucose monitor might notice they’ve become extremely sensitive to carbs and experience a higher-than-normal glucose spike after transitioning back from keto —even if they only eat a small number of carbs. They may also feel very tired or experience digestive issues when they reintroduce the carbs they once enjoyed, and even regain a bit of weight due to higher insulin levels.
This phenomenon (known as carbohydrate intolerance) is a normal response when the body is adapting to these changes in diet. That’s because your metabolism is like a hybrid car that can use both gas and electric power for energy (i.e., fat and carbs). However, unlike hybrid cars, if you’ve been limiting your body to one source of energy (fat), it’ll take some time to gradually become efficient at using the other one (carbs) again.
Carbohydrate sensitivity or intolerance after keto: what it means
Carbohydrate sensitivity or intolerance is a condition where your body has difficulty properly metabolizing carbohydrates —which is also known as temporary insulin resistance.
Your body's cells temporarily become less responsive to the hormone insulin. Insulin regulates blood sugar levels by helping to transport glucose from the bloodstream into the cells, where it can be used as a source of energy [3]. When you have temporary insulin resistance, cells do not respond to insulin as well as they should, leading to elevated blood sugar levels.
Sensitivity to carbs can also result in a variety of symptoms, including abdominal pain, bloating, gas, diarrhea, constipation, and fatigue.
Slowly reintroducing carbs can help the process, starting with foods that have a low glycemic index. Over time, the temporary insulin resistance and carb sensitivity will subside.
If you’ve been on keto for a while (say, one year or longer), you may be wondering how long it will take your body to overcome your carb sensitivity. Right now, there isn't much available literature on long-term keto diets —many studies that follow "long-term keto" participants only last about 6 months.
For most people, however, it can take about 2 weeks to readjust to carbs (though this likely won't be as much of an issue if you've only done keto for a few days).
Key takeaways: how to add carbs back into your diet
When you want to add carbohydrates back into your diet after following keto, it’s important to allow your body to adjust over time. Remember that this is a slow transition (just like starting keto was!), so be patient and keep track of how you feel.
However, since the thing that people tend to miss in a low-carb/keto diet is fiber, you may experience a bit of gastrointestinal discomfort —which is why slowly reintroducing carbs (especially fiber) is key. This is also helpful for maintaining weight loss since fiber intake is associated with more successful weight loss [4].
To start, estimate the number of carbs you are eating in a day on keto and increase that by 25% every week until you hit the number of carbs you’d like to be eating on a regular basis. The key is to work your way up gradually —if you experience constipation, increased appetite (to the point of overeating), energy crashes, or other unusual symptoms, ease up on your carb intake. Mild bloating or fatigue may last a little longer but will dissipate as your body adjusts.
- Some other strategies that may be helpful in preventing spikes in blood sugar include:
Eat fiber (vegetables) and proteins/fats first, and carbs last. (This slows the absorption of glucose into your bloodstream.) - Drink a 10-ounce glass of water with a tablespoon of apple cider vinegar before or during your meal to reduce postprandial glucose spikes.
- Avoid eating carbs later in the evening, when your body is less sensitive to insulin. Incorporating post-meal walks into your daily routine (even just 2-15 minutes)..
- Exercising regularly (preferably both aerobic and resistance training) to improve insulin sensitivity and cardiometabolic health.
- Getting adequate sleep to live in alignment with your body clock. (One night of bad sleep can disrupt your body’s ability to regulate glucose.)
- Use a CGM to track your progress as you reintroduce carbs back into your diet and give you insights into your body’s intolerance to carbs.
References:
- https://www.mdpi.com/2072-6643/9/5/517?utm_source
- https://www.ncbi.nlm.nih.gov/books/NBK499830
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1204764
- https://www.acpjournals.org/doi/10.7326/M14-0611?articleid=2118594
FAQs
Carbohydrate intolerance, or a more sensitive response to eating carbs, can occur after following a ketogenic diet as your body becomes more efficient at using fat as a fuel source and less efficient at using carbohydrates.
Why am I so sensitive to carbs after keto? ›
Key Takeaways. It's been known for more than a hundred years that carbohydrate intolerance can skyrocket within two days on a ketogenic diet. On a high-fat diet, blood sugar response can be nearly double what it may be on a high-carb diet.
How to reintroduce carbs after keto? ›
Add in an additional 10 g of carbohydrates per day for the first week, says Keene. Opt for carbs from healthy sources like whole grains, beans, fruits, and starchy veggies. Grab a pad of paper and track your weight and how you feel.
What causes carbohydrate intolerance? ›
Patients with hypokalemia tend to develop carbohydrate intolerance. Hyperkalemia stimulates insulin release, whereas hypokalemia mildly inhibits insulin release. Therefore, hypokalemia blunts insulin secretion in response to the rise in blood glucose levels, which leads to carbohydrate intolerance.
Why do I have carb bloat after keto? ›
After going keto, it takes time for your gut's ecosystem to adjust to new foods. This is especially true if you've increased your sugar alcohol and MCT consumption. Changes in dietary fiber intake can also impact your gut flora. As a result, your gut may become overblown with bad bacteria, a known trigger for bloating.
What happens when you eat carbs after keto? ›
“When you reintroduce carbohydrates back into your diet — and this is more about refined carbs, I'm not talking about eating an apple — you don't feel very good.” She says some people experience a so-called carb hangover — the body feels kind of bloated and inflamed, and you may develop headaches.
How do I fix my gut after keto? ›
Focus on Fiber-Rich Low Carb Foods: While the keto diet restricts carbohydrates, you can still include fiber-rich low carb foods such as leafy greens, cruciferous vegetables (e.g., broccoli, cauliflower), avocados, and berries. These provide essential nutrients and support a healthy gut environment.
How to reverse carbohydrate intolerance? ›
To reverse carbohydrate intolerance, it's important to add carbs back in slowly, starting with small servings and low-GI foods like fruits, vegetables, and whole grains. These foods have “good carbs,” which are higher in fiber, which can help prevent large blood sugar spikes.
What to eat if you have carbohydrate intolerance? ›
Rather than completely restricting carbohydrate intake, it's better to incorporate lean proteins, healthy fats, and fruits and vegetables with lots of dietary fiber on a daily basis. Healthy fats include olive oil, avocados, nuts, and seeds.
What is the best diet to transition to after keto? ›
Instead, concentrate on a diet that is rich in lean proteins, healthy fats and complex carbs. A good model to follow is the Mediterranean diet. Call on the same discipline that allowed you to stick to keto, and choose high-quality carbs, lean proteins and healthy fat.
Carbohydrate maldigestion is when the body is lacking enzymes to digest carbohydrates, a common example being lactose intolerance. Carbohydrate malabsorption is an inability of carbohydrates to move across the intestinal wall into the bloodstream to be used by the body, a few common examples being SIBO and leaky gut.
What does carb inflammation feel like? ›
This achy feeling may appear as stiff joints, achy muscles, migraines, added asthma or PMS symptoms.
What is the most common carbohydrate intolerance? ›
The most common type of carbohydrate intolerance is lactose intolerance due to a primary insufficiency of the lactose digesting enzyme, lactase. Humans, being mammals, are genetically programmed to have reduced lactase activity once the weaning process begins.
Can you develop carb intolerance after keto? ›
Essentially, when there is too much fat in the diet, as is the case for a ketogenic diet or the typical American diet, the body's ability to burn the carbs we eat goes down. Which means that when we reintroduce carbs after a ketogenic diet, our body doesn't know how to handle the carbohydrates.
How do I transition back to carbs after keto? ›
As a general rule of thumb, try to limit your intake of new carbs to 1 or 2 servings, or about 10 g of carbs per week for the first 2 weeks. Introducing carbs gradually will give your body time to adjust and help you avoid gastrointestinal issues.
What is keto whoosh? ›
These keto dieters say the fat on their body starts to feel softer to the touch. The concept of the whoosh effect is if you stay on the diet long enough, your cells start to release all the water and fat that's thought to have built up. When this process begins, this is called the “whoosh” effect.
What are keto carb withdrawal symptoms? ›
Nausea, constipation, headaches, fatigue and sugar cravings are common in some people who are adapting to a high-fat, low-carb diet. Staying hydrated, replacing lost electrolytes, getting enough rest and ensuring you are consuming proper amounts of fat and carbohydrates are ways to reduce keto-flu symptoms.
What is the keto refeeding syndrome? ›
In refeeding syndrome, chronic whole body depletion of phosphorus occurs. Also, the insulin surge causes a greatly increased uptake and use of phosphate in the cells. These changes lead to a deficit in intracellular as well as extracellular phosphorus.
Can eating carbs after keto cause headaches? ›
Yes, eating a large amount of carbohydrates after following a ketogenic diet can result in digestive discomfort and other symptoms, such as bloating, gas, diarrhea, headaches, fatigue, and mood swings. This is often due to the sudden change in the body's metabolism and hormone levels.
What is carb adaptation after keto? ›
Keto-adaptation is a period of the time period when you are in ketosis and you have a high-carb meal. This can cause your body to enter a state of keto-flu, which is when your blood sugar drops and your body feels confused. Your body will react to the large meal by releasing stored fats and carbohydrates.
