Side Effects of the Paleo Diet

Paleo diets focus on foods that Paleolithic man caught or gathered: free-range meat, eggs, seafood, vegetables, fruits, seeds and nuts. You may experience better health with a diet that humans have eaten for thousands of years, explains Robb Wolf, author of "The Paleo Solution: The Original Human Diet," than with a modern diet high in grains, sugars and processed foods, which humans have eaten for a much shorter period. Wolf, a former research biochemist, is a Paleolithic nutrition expert. Shifting from the USDA food pyramid to a Paleo diet may cause some side effects. Check with your doctor before changing your diet.

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Low-Carb Flu

Some people experience lethargy, fatigue, irritability and shakiness when first eliminating starches, grains and legumes from their diet, explains Sébastien Noel, of Paleo Diet Lifestyle. Although you can eat sufficient carbs from plants on the Paleo diet, the change in overall carb consumption may be quite dramatic if your former diet was heavy on breads, pastas and beans. The low-carb flu symptoms usually last at most three to four weeks, says Noel. During this time, your body shifts into burning fats as a fuel source instead of carbohydrates. You can reduce the low-carb flu effect by gradually lowering your carbohydrate consumption, instead of going cold turkey on your diet overhaul.

Ketogenic Breath

As your body shifts to primarily burning fat, instead of carbohydrates, for energy, you will shift into a process called ketosis. Acetone is a byproduct of ketosis, and it carries a distinct scent. This is normal and usually not a sign for concern, notes Noel. The exact amount differs from person to person, based on size and activity level. Avoid potatoes, rice and grains, as they are higher in carbs and contain fewer nutrients. Chewing on mint or cilantro can take the edge off ketogenic breath, as well.


Some people on long-term low-carbohydrate diets report hypothyroid symptoms, such as fatigue, sluggishness and sensitivity to cold, reports Noel. Low-carb dieting suppresses your appetite, which can eventually send your body into starvation mode. If you lose too much weight, your body down-regulates thyroid function to save energy. You can avoid this by eating larger amounts of Paleo-permitted vegetables to keep your carbohydrate levels up.


You might experience cravings for sugar and other non-Paleo options like French fries or potato chips during the first couple of weeks of transitioning to a Paleo diet, according to Sarah Fragoso, author of "Everyday Paleo." This is always followed by an increase in energy and mental clarity. The cravings cease and most people report no longer desperately desiring sweets and treats like those that they have on other diets, she explains. Fragoso is a strength and conditioning coach and a certified Level 1 Crossfit Trainer.

Excess Protein

The Paleo diet includes large amounts of animal protein -- meat, shellfish, poultry, eggs and fish. Except for fish, which has less total fat, these foods are high in saturated fat and cholesterol. Excess animal protein consumption elevates blood levels of bad LDL cholesterol, decreases good HDL cholesterol and increases your risk of heart disease. Your kidneys process the by-products of protein metabolism. Because of the high-protein content of the Paleo diet, your kidneys have to work harder to remove the additional waste products, according to Martha Filipic, technical editor for Chow Line, Ohio State University's nutrition column.

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