High-protein diets restrict carbohydrates, which normally make up more than half of the calories in your diet. In a normal 2,000-calorie diet, you consume approximately 225 to 325 g of carbohydrates and 50 to 175 g of protein. A high-protein, low-carb diet increases your protein intake and drops your carb consumption to as low as 20 g per day. Since you're replacing carbs with protein, you may consume two or three times as much protein than normal. High protein diets can have adverse effects on your health and should only be followed for a short period of time. Talk with your doctor before you decide to make any changes to your diet.
Irregularity
Since high protein diets drastically limit or exclude fruits, vegetables and whole-grains, you may experience irregularity. These foods are rich in a type of indigestible carbohydrate called fiber. While fiber doesn't break down in your digestive tract, it aids digestion. Having inadequate fiber intake can lead to constipation, gas, bloating, abdominal cramping or diarrhea. Being irregular for an extended period of time may increase your risk of hemorrhoids and diverticulitis, a condition that forms pouches throughout intestinal walls where food can get stuck and cause inflammation.
Increased Cholesterol
Having a diet too high in protein may cause you to eat large amounts of animal foods, such as meat, cheese and dairy. While these foods are healthy in small portions, too much can have adverse health effects. Animal foods contain saturated fat, a type of unhealthy fat that can raise your low-density lipoprotein, or LDL cholesterol, as well as your total cholesterol. As your blood cholesterol rises, your risk of heart disease also increases. If you follow a high-protein diet, enjoy lean meats and low-fat or skim dairy products, in place of full-fat animal foods.
Fatigue
A diet too high in protein may cause you to feel weak and fatigued. According to research published in the "Journal of the American Dietetic Association" in 2007, ketones in your blood increase fatigue. Ketones are by-products formed when your body is forced to metabolize fat, instead of carbohydrates for energy. While small amounts of ketones are safe once in awhile, continuous high levels can be damaging. In the study, subjects following a ketogenic, or high-protein diet, had elevated beta-hydroxybutyrate at the end of the two-week period. When elevated, beta-hydroxybutyrate leads to fatigue and can reduce your desire to exercise.
Strain on Kidneys
A diet too high in protein can put added strain on your kidneys. When you have constant ketones in your blood, your kidneys work hard to excrete them, since they are toxic and can cause permanent damage to organs. Your kidneys pull water from all over your body in order to dilute ketones so they can be excreted through urine. This can lead to kidney problems or worsen current kidney problems, explains Katherine Zeratsky, a registered dietitian of MayoClinic.com.
References
- MayoClinic.com: High-Protein Diets: Are They Safe?; Katherine Zeratsky, R.D., L.D.; June 2010
- Medline Plus: Protein in Diet; July 2009
- Colorado State University: Dietary Fiber; J. Anderson, et al, January 2011
- "Journal of the American Dietetic Association": Blood Ketones are Directly Related to Fatigue and Perceived Effort During Exercise in Overweight Adults Adhering to Low-Carbohydrate Diets for Weight Loss: A Pilot Study.; A.M. White, et al; October 2007
- MayoClinic.com: Low-Carb Diet; May 2010
- McKinley Health Center: Macronutrients: The Importance of Carbohydrate, Protein, and Fat; March 2008
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