Low-carb, high-protein diets restrict your intake of grains, starchy vegetables and sugars, and increase your intake of protein and fat. A study published in Annals of Internal Medicine in September 2014 found that this type of diet was more effective for weight loss than a low-fat diet. Low-carb, high-protein diets may also improve cholesterol profiles and help with blood sugar control in diabetics. However, this eating plan also has drawbacks, including kidney damage and increased risk of heart disease.
Grams of Carbs in a Low-Carb Diet
The Dietary Guidelines for Americans 2010 recommends adults get 45 to 65 percent of daily calories from carbohydrates, your body's main source of energy. That's about 225 to 325 grams of carbs each day. Low-carb diets recommend significantly fewer carbs -- 60 to 130 grams per day, according to MayoClinic.org. Some diets, such as the Atkins diet, go even lower, allowing only 20 grams of net carbs -- carbs minus fiber -- in the first phase.
When you reduce your carbs, you need to increase your protein and fat intake to make up the extra calories. In a high-protein, low-carb diet, a good part of those extra calories will come from protein.
How Low-Carb Diets Work
Low-carb, high-protein diets can encourage weight loss because you're automatically cutting out some unhealthy, calorie-rich foods, such as cake, cookies, candy, ice cream and sugary beverages. You're also cutting down on foods such as potatoes that, although nutrient-rich, are also high in starches that are converted to sugar in your body and then enter your bloodstream as blood sugar, or glucose.Your body uses blood sugar to fuel all your activities, but excess glucose is stored as fat. On a low-carb diet, your body begins to use fat as a primary energy source.
Because protein is the most satiating nutrient, it can help you control your calorie intake while losing weight. Protein may also stimulate thermogenesis, or increased metabolic activity, during digestion, according to a study published in The American Journal of Clinical Nutrition in January 2011.
Low-Carb Dieters Fared in Studies
In the 2014 Annals of Internal Medicine study, the low-carb group lost an average of 8 pounds more than the low-fat group in one year. The low-carbers also lost more body fat and had higher levels of good cholesterol and lower levels of triglycerides than the low-fat group.
The results of a 12-week study published in The Journal of Pediatrics in March 2003 found that adolescents on a low-carb diet lost 11 pounds more than those on a low-fat diet.
A study published in Diabetes in September 2004 found that a five-week low-carb, high-protein diet dramatically lowered circulating blood sugar concentrations in participants with untreated diabetes.
Restricting carb intake to fewer than 20 grams per day can cause ketosis, a process in which your body breaks down fat for energy. This causes substances called ketones to build up in the blood and can lead to symptoms such as headache, nausea, bad breath and mental and physical fatigue.
A diet high in protein can increase your intake of saturated fat, an unhealthy type of fat from animal foods that can cause heart disease. A study published in BMJ in June 2012 found that regular adherence to a low-carb, high-protein diet, without consideration of the type of carb or protein, was associated with an increased risk of heart disease in Swedish women aged 30 to 49 years over a 16-year period.
A low-carb diet can also put strain on your kidneys and worsen existing kidney problems. Your risk of osteoporosis and kidney stones may be higher as well since you may lose more calcium through increased urination on a high-protein diet.
A Healthy Middle Ground
Complex carbohydrates such as whole grains, fruits and vegetables are healthy parts of a balanced diet. They are rich sources of dietary fiber, which you need for digestive health, as well as key vitamins and minerals. Rather than cut out these healthy foods, instead cut out sugary foods and refined-grain products such as white rice and white bread. Eat more nonstarchy vegetables and choose lean proteins such as white meat chicken, fish, tofu and beans to lower your saturated fat intake.