What to know about Low Carb Diets

Everywhere you look you can find low-carbohydrate (or high- protein) diet books, foods, advertisements, and even stores. These diets promise fast, effective weight loss and have been around since the 1970s. Many Americans have testified to their effectiveness—at least for the short-term—and have readily embraced them. Health professionals, on the other hand, have remained skeptical because of their potentially harmful effects. So, what is the skinny on low-carbohydrate diets? This fact sheet provides an overview of two of the most popular diets, along with the pros and cons of weight loss and health with these diets.

What are low-carbohydrate diets?

The meaning of “low carbohydrate” varies from diet to diet. Some diets recommend extreme restriction of all carbohydrates, while others merely limit carbohydrates to primarily whole grains. What “low carbohydrate” means really depends on the diet and how it is followed. Two of the most popular diets, the Atkins and South Beach diets, show this contrast.

What are the benefits?

Weight Loss

One of the biggest benefits of low-carbohydrate (high-protein) diets is short-term weight loss. This is one reason that they have been so successful. In fact, compared to a traditional low-fat, high-carbohydrate, low-calorie diet, these diets have been shown to result in greater weight loss in studies lasting less than six months. In a few studies carried out for one year, dieters on the Atkins diet lost more initial body weight com- pared to the low-fat group and at the end of six months. At one year, however, the Atkins diet group gained back more weight compared to the low-fat diet group with the end weight loss being similar for the two groups at the end of the studies.
Many scientists argue that the short-term greater weight loss for individuals on the Atkins diet is due to fewer calories, not necessarily because of the lack of carbohydrates. Weight loss may also be in the form of muscle, not fat.


Diets high in saturated fat and dietary cholesterol are known to raise LDL, “bad” cholesterol, and lower HDL, “good” cholesterol, in long-term studies. Although low-carbohydrate (high-protein) diets typically include foods high in saturated fat and cholesterol, to date, studies have indicated that they do not positively or negatively change total cholesterol, LDL cholesterol, or HDL cholesterol in short-term studies. These diets do have a positive impact on triglycerides. Levels went down in all reported stud- ies. High triglycerides in combination with low HDL cholesterol levels are risk factors for heart disease.
LDL = “Bad” cholesterol; High LDL linked to higher risk of heart disease
HDL = “Good” cholesterol; High HDL linked with lower risk of heart disease
In this case, weight loss, not the saturated fat and cholesterol in the diet, may be the reason that cholesterol is not changed. It is unclear what would happen to cholesterol levels if the diet were followed over an extended period of time.

What foods are not part of low carbohydrate diets?

One of the biggest concerns with restrictive, low-carbohydrate diets is the elimination of certain foods and food groups. There are definitely some foods in each food group that offer more nutrients than others, such as whole-grain foods versus refined grains like white bread and sweet rolls. Still, there are numerous studies showing that healthy choices and sensible portion sizes from all of the food groups of the Food Guide Pyramid, combined with physical activity, help achieve a healthy weight – and promote lifelong health. Protein and fat alone cannot provide you with the nutrients you need for good health, which is not necessarily the same thing as weight loss. Vitamin and mineral supplements are just that – “supplements” – and should not be used as replacements. They do not offer the same benefits as vitamins and minerals obtained from “real” foods.
Following is a list of some of the nutritional benefits that are lost as a result of restrictive carbohydrate diets:

• Breads, cereals, and grains – especially whole grains – pro- vide excellent sources of fiber and B vitamins, like folic acid, which helps promote heart health and prevent childbearing women from having babies with neural tube defects.
• Carbohydrates are the best source of energy for your brain and body, especially if you are active. Protein and fat are not as efficient sources of energy; they need to be converted into energy units that you can use. Many people complain about being fatigued and getting headaches on low-carbohydrate diets because of this.
• Fruits and vegetables are rich sources of fiber, vitamins, minerals, and phytochemicals that help protect against disease. Fruits, despite their numerous benefits, are not recommended in low-carbohydrate diets because they naturally contain sugar.
• Dairy products are excellent sources of calcium and vita- min D for strong bones and teeth, but because they also contain natural sugars, they are also avoided in many diets.
• Nuts provide healthy sources of fat, such as omega-3 fatty acids, which help protect against heart disease.
• Fiber, which is found in most of the foods that are eliminated in low-carbohydrate diets, helps give you the feeling of being full.

Are all fats and high protein foods created equally?

Although many of the low-carbohydrate diets stress the importance of eating proteins and not worrying about fat, it is important to distinguish between healthier and unhealthier choices. High-fat meats, heavy cream, butter, and gravy con- tain saturated fat and cholesterol, which can contribute to an elevated risk of heart disease.

Try to limit saturated fat by choosing lean meats or beans, low-fat dairy products, and  fish and nuts that are high in omega-3 fatty acids, considered beneficial for the heart.

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