Side effects of eating Paleo or low-carb

Changing your diet from a high-carb, low-fat standard American diet to a lower carb and higher fat diet requires your body some time to adapt. In the meantime, you may experience some short-time and transient side effects. These side effects are not dangerous but can be a bit annoying. Most of them are preventable if you follow these simple tips.

What are the possible side effects that may occur when getting started with the Paleo diet?

  • Headache
  • Fatigue
  • Lack of energy
  • Lack of concentration
  • Weakness
  • Light-headedness
  • Dizziness
  • Irritability
  • Constipation or diarrhea
  • Body aches
  • Cold sweats
  • Nausea
  • Cravings

Can the Paleo diet or low-carb diet cause side effects?


What are causing these side effects?

  • Fat-adaptation: if you used to consume a high-carb, low-fat diet, switching to a lower-carb and higher-fat Paleo diet will require your body to transition from being a sugar-burner to being a fat-burner.
  • Mild dehydration: A high-carb diet can make you retain more water in your body, while a lower-carb diet has a diuretic effect and allows you to get rid of this extra unnecessary water. If you lose this extra water too fast however, you could experience symptoms of mild dehydration. Read the section on how to prevent or alleviate the potential side effects of mild dehydration and avoid suffering unnecessarily.
  • Withdrawal symptoms: grains, dairy and sugar are addictive and can have a strong effect on your brain chemistry, just like drugs but to a lesser degree. Eliminating these foods from your diet can cause a withdrawal reaction as your body learns how to function without these substances. The 4-week Paleo challenge is a good way to get rid of your food addictions.

How long does it last?

The side effects may start within 12 hours of getting started on the Paleo diet and usually resolve within 4 to 5 days, although it can last for up to 2 to 4 weeks in some people.

How to prevent or alleviate potential side effects?

  • Eat enough fat: the Paleo diet is lower in carbs compared to the standard American diet, which is high in carbs and low in fat. When switching to the Paleo way of eating, you need to make sure you provide your body with enough energy to allow you to function optimally. Fat is the solution! As a general rule of thumb, most people benefit from including about 1 to 2 tbsp. of extra natural fat, from coconut oil, ghee, extra-virgin olive oil or even butter, at each of your meals*Avocado, coconut, olives, nuts and nut butter are also good ways to increase your fat intake to help your body adjusts from being a sugar-burner to becoming a fat-burner. (*Had your gallbladder removed? Read the last part of this post.)
  • Eat at regular intervals: you may have heard of people practicing intermittent fasting, skipping meals  or restricting their eating within a 8-hour window on the Paleo diet, but if you are new to Paleo eating and especially if you have blood sugar issues, make sure you eat at regular intervals until your blood sugar levels stabilize and until your body becomes completely fat-adapted.
  • Drink enough water: because decreasing your carb intake can have a diuretic effect, make sure you stay properly hydrated and avoid the symptoms caused by mild dehydration by drinking a minimum of 2L of fluids (water, sprinkling water, tea, herbal tea or homemade broth).
  • Supplement with salt*: to prevent experiencing side effects due to the diuretic and mildly dehydrating effect of a lower-carb Paleo diet, add a bit more salt to your diet to help you retain enough water in your body. Crystal mineral-rich salts, such as Himalayan salt, Murray River salt or Celtic sea salt, are best. Sprinkle about ½ tsp. per day over your food*. Alternatively, you can drink about 2 cups of homemade salted bone broth or use about 2 tbsp. of wheat-free tamari sauce to replenish your electrolytes and prevent, or at least alleviate, side effects.
  • Consult your doctor*: some of the side effects you may experience when starting eating Paleo could be due to a lack of adjustment to your medications. If you have a medical condition or take prescribed medications, especially diabetic or blood pressure medications, consult your doctor to make sure the dosage is adjusted appropriately.
  • Slow down: during the first 2 weeks or until your body is fully acclimated to the Paleo diet, it may be a good idea to avoid high-intensity physical activity. Walking and other low-intensity exercises should be fine, but listen to your body. If you experience low energy and fatigue, take some time to rest to allow your body to gently adapt to your new way of eating.
  • Stick to it and be patientbe patient and resist the temptations and within a couple of weeks, things will get a lot easier and you may even notice an improvement in your energy levels and well-being. Give yourself at least 28 days or 4 weeks to make sure you are able to go past the potential short-term side effects and start noticing the benefits of eating Paleo.


*Special considerations:

Always check with your doctor first before making any changes to your diet, especially if you decide to try the Paleo diet and/or lower your carb intake by cutting out grains and sugar and/or increase your fat and/or sodium or salt intake. If you have blood sugar issues, diabetes, hypertension or any other medical conditions and/or take prescribed medications, consult your doctor or registered dietitian for help during the transition to a lower carb diet. Decreasing your carb intake can rapidly lower your blood sugar levels, blood pressure and other health parameters, which may require prompt adjustments to your medications or medical treatment.

★ If your doctor is not familiar with low-carb / Paleo diets, consult the Paleo Physician NetworkPrimalDocs or Jimmy Moore’s list of Low-Carb Doctors.


*If your gallbladder was removed (cholecystectomy) or if you were used to eating a low-fat diet, make sure you increase your fat intake gradually when starting on the Paleo diet to help your body adjust by secreting adequate amounts of digestive enzymes. Some people may benefit from supplementing with digestive enzymes and ox bile to facilitate fat digestion. Consult a health professional for advice in this regard.