The ketogenic diet has gained popularity as a way to lose weight and potentially improve your health. The diet is very low in carbohydrates, high in fat, and moderate in protein. While the diet is considered safe for most people, it’s associated with some unpleasant initial side effects. Some followers of the diet refer to this as the “keto flu” or "carb flu." This article investigates the causes of muscle cramps during a low-carb diet and how to ease its symptoms.
Understanding the Keto Flu
The keto flu is a collection of symptoms experienced by some people when they first start the keto diet. These symptoms, which can feel similar to the flu, are caused by the body adapting to a new diet consisting of very little carbohydrates. Reducing your carb intake forces your body to burn ketones for energy instead of glucose. Ketones are byproducts of fat breakdown and become the primary fuel source when following a ketogenic diet. Usually, fat is reserved as a secondary fuel source to use when glucose is not available. This switch to burning fat for energy is called ketosis. It occurs during specific circumstances, including starvation and fasting. However, ketosis can also be reached by adopting a very low carb diet. This drastic reduction can come as a shock to the body and may cause withdrawal-like symptoms similar to those experienced when weaning off an addictive substance like caffeine. Switching to a very low carb diet is a major change, and your body may need time to adapt to this new way of eating. For some people, this transition period can be especially difficult. Signs of the keto flu may start popping up within the first few days of cutting back on carbs. Symptoms can range from mild to severe and vary from person to person. While some people may transition to a ketogenic diet without any side effects, others report symptoms.
Common symptoms include:
- Nausea
- Vomiting
- Constipation
- Diarrhea
- Headache
- Irritability
- Weakness
- Muscle cramps
- Dizziness
- Brain fog
- Stomach or intestinal pain
- Muscle soreness
- Difficulty sleeping
- Food cravings
These symptoms are commonly reported by those who have just begun the ketogenic diet and can be distressing. Symptoms typically last a few days or, rarely, up to several weeks. While these side effects may cause some dieters to give up, there are ways to reduce them.
Muscle Spasms and the Keto Diet
Muscle spasms are a common and frustrating side effect experienced by many following a ketogenic diet. While keto offers benefits like weight loss and improved metabolic health, the drastic reduction in carbohydrates can cause electrolyte imbalances that trigger muscle cramps and spasms. Understanding why these spasms occur-and how to address them-is key to maintaining comfort and sustaining your keto lifestyle effectively.
Read also: Safety of Low-Carb Diets During Lactation
Why Keto Causes Muscle Spasms
The ketogenic diet drastically reduces carbohydrate intake, which causes the body to use stored glycogen for energy. Glycogen holds water in the muscles, so when glycogen is depleted, water and electrolytes like sodium and potassium are also lost through urine. This imbalance disrupts muscle function, leading to spasms. Magnesium deficiency, common on keto, further contributes by impairing muscle relaxation.
Common Causes of Keto Muscle Spasms
- Electrolyte depletion (sodium, potassium, magnesium)
- Dehydration from increased water loss
- Changes in muscle energy metabolism
- Inadequate mineral intake during keto adaptation
Symptoms to Watch For
- Sudden, involuntary muscle cramps (often in legs or feet)
- Persistent twitching or tightness
- Muscle soreness after mild activity
- Nighttime leg cramps disrupting sleep
Electrolyte Imbalance: A Key Culprit
A potential cause of leg cramps is an electrolyte imbalance. Electrolytes are positively charged minerals that play a vital role in many bodily functions, particularly those involving muscles and nerves. They’re present in fluids like blood, sweat, and urine, and they help move fluids in and out of your cells, support muscle contraction and relaxation, and assist with nerve signaling. Electrolytes are minerals that are essential for critical functions in your body, such as cell communication. They include sodium, magnesium, chloride, potassium, calcium, phosphate, and bicarbonates. If your levels become depleted, your nerve cells may become more sensitive. In turn, this leads to pressure on nerve endings, which may cause muscle spasms. When adapting to the keto diet, your body may lose more electrolytes through urination in response to decreased levels of blood sugar and the hormone insulin. This loss is typically greatest during the first 1-4 days of transitioning to keto, so muscle cramps related to electrolyte imbalance may be worse during this period.
When following a ketogenic diet, levels of insulin, an important hormone that helps the body absorb glucose from the bloodstream, decrease. When insulin levels decrease, the kidneys release excess sodium from the body. Furthermore, the keto diet restricts many foods that are high in potassium, including fruits, beans, and starchy vegetables.
The Role of Specific Electrolytes
- Potassium: Potassium plays a vital role in cellular energy balance by supporting fluid regulation and the transport of nutrients and waste across cell membranes. It also works alongside sodium, calcium, and magnesium to coordinate muscle contraction and relaxation.
- Magnesium: Magnesium is the fourth most abundant mineral in the body and is essential for health. Magnesium and calcium work together to regulate muscle and nerve activity. While calcium stimulates muscle contraction, magnesium promotes relaxation.
- Sodium: Sodium plays a critical role in maintaining fluid balance both inside and outside of cells and serves as a cofactor in muscle contraction and nerve function. It also helps regulate the balance of other key electrolytes, including potassium and magnesium.
Dehydration and Muscle Cramps
People transitioning to the keto diet often urinate more due to factors like reduced insulin levels and increased sodium excretion. In turn, increased urination can lead to dehydration, another potential cause of leg cramps. Dehydration is one of the most common keto side effects and may thus increase your risk of leg cramps.
A keto diet can cause you to rapidly shed water stores, increasing the risk of dehydration. This is because glycogen, the stored form of carbohydrates, binds to water in the body. When dietary carbohydrates are reduced, glycogen levels plummet, and water is excreted from the body.
Read also: Best keto-friendly chips
Solutions That Help
- Replenish electrolytes through diet and supplements
- Stay well-hydrated with water and mineral-rich fluids
- Incorporate magnesium and potassium-rich foods
- Moderate exercise and stretching routines
- Consult a healthcare provider if spasms persist
Electrolyte Management Is Key
Replacing lost electrolytes is critical to preventing and relieving keto muscle spasms. Foods rich in potassium (avocados, leafy greens), magnesium (nuts, seeds), and sodium (broth, salted foods) should be prioritized. Many people also benefit from targeted supplementation under medical guidance, especially during the early adaptation phase.
To help maintain adequate potassium, it’s important to include potassium-rich foods in your diet. While many high-potassium foods like sweet potatoes, lentils, and coconut water are too high in carbohydrates for a ketogenic diet, there are plenty of keto-friendly options. Leafy greens such as beet greens, Swiss chard, and spinach are excellent sources, as are vegetables like mushrooms, Brussels sprouts, zucchini, broccoli, and asparagus. To support healthy magnesium levels, it’s important to include magnesium-rich, keto-friendly foods in your diet. Leafy greens such as spinach and Swiss chard are excellent sources, as are avocados, hemp seeds, chia seeds, and pumpkin seeds. To help maintain sodium balance on a keto diet - especially during the keto adaptation phase - consider adding a pinch of Himalayan or sea salt to your meals or water throughout the day. These unrefined salts provide sodium along with lesser amounts of trace minerals.
Hydration Strategies
Keto causes a natural diuretic effect, increasing water loss. Proper hydration isn’t just about drinking more water-it requires balancing electrolytes to maintain cellular function. Drinking mineral-enhanced water or electrolyte drinks without added sugars can support muscle health and reduce spasms. Staying hydrated can help with symptoms like fatigue and muscle cramping. Replacing fluids is especially important when you are experiencing keto-flu-associated diarrhea, which can cause additional fluid loss.
One of the simplest and most effective ways to support hydration is to drink water consistently throughout the day. A general guideline is to consume at least half your body weight in ounces of water daily. For instance, if you weigh 150 pounds, aim for around 75 ounces (2.6 liters) of water. If you’re physically active while following a ketogenic diet, it’s especially important to hydrate before, during, and after your workouts. Adding mineral drops to your water is a convenient option; these typically contain concentrated trace elements that support electrolyte balance. Keto-friendly electrolyte powders can also be useful, particularly after exercise or periods of heavy sweating. These are typically free of added sugars and can be mixed into water or smoothies.
Exercise and Muscle Care
While exercise is important, overexertion can worsen spasms if electrolytes aren’t balanced. Incorporate gentle stretching, yoga, or light resistance training to improve muscle tone and flexibility. Avoid intense workouts until your body fully adapts to keto. Prolonged sitting is associated with various health concerns, including increased risk of muscle cramps. If you spend much of your day at a desk, make it a point to stand up, stretch, and move your body regularly. Setting a reminder to walk or gently stretch every couple of hours can help promote circulation and reduce muscle tension. While exercise is important for staying healthy, strenuous exercise should be avoided when experiencing keto-flu symptoms. Fatigue, muscle cramps, and stomach discomfort are common in the first week of following a ketogenic diet, so it may be a good idea to give your body a rest. Activities like intense biking, running, weightlifting, and strenuous workouts may have to be put on the back burner while your system adapts to new fuel sources. While these types of exercise should be avoided if you are experiencing the keto flu, light activities like walking, yoga, or leisurely biking may improve symptoms.
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Food to Eat
- Avocados
- Leafy greens such as beet greens, Swiss chard, and spinach
- Vegetables like mushrooms, Brussels sprouts, zucchini, broccoli, and asparagus
- Hemp seeds
- Chia seeds
- Pumpkin seeds
Additional Tips for Managing Muscle Cramps
- Stay hydrated: Drink plenty of water throughout the day.
- Consume enough salt: Salt your food and consider sipping on salted bone broth to reduce the chances of electrolyte imbalance.
- Cut back on or avoid alcohol: Alcohol is a diuretic and may worsen dehydration.
- Engage in gentle exercise: Try walking, stretching, and yoga when first adapting to keto. Avoid intense exercise for the first few days to reduce the chance of leg cramps.
- Get adequate sleep: Fatigue and irritability are common complaints of people who are adapting to a ketogenic diet.
When to Seek Professional Help
If muscle spasms persist despite lifestyle adjustments, underlying conditions such as mineral absorption issues, thyroid dysfunction, or neurological problems may be involved. If you have persistent or extreme leg cramps, you should visit a health professional to ensure that you’re not experiencing symptoms of a more serious medical condition. Blood tests measuring CRP, ESR, hormone panels can help identify underlying inflammation and imbalances.