logo for medical-weight-loss-guide.com
leftimage for medical-weight-loss-guide.com

Low Carb Diet
(or Low Carbohydrate Diet)

Basics

pasta shellsA low carb diet restricts the amount of carbohydrates you eat. The Atkins and the South Beach diets are two examples. These types of diets generally recommend somewhere between 20-60 grams of carbohydrates per day. That comes out to about 20% of your daily calories. To make up for having less carbs, these diets give you more of your calories from fat and protein.

Most of the low carb diet plans have different phases. First, there is an initiation phase which has the lowest amount of carbohydrates. Not eating many carbs will cause your body to use fat and protein for energy. When fats are mostly used for energy, your body enters a state called ketosis. Your blood becomes more acidic and accumulates chemicals called ketones. This state can be detected by checking your urine.

There may be health consequences for going into ketosis, so you should discuss this with your doctor. After the initiation phase, carbohydrates are slowly added back to your diet until weight loss stops and you reach a steady weight.

Some people claim that these diets cause weight loss from the effects of lowering carbohydrates in your diet. However, these diets really end up being low calorie diets with a high amount of protein. Protein makes you feel more full than carbohydrates do. That makes it easier to eat less. In the end, weight loss comes from eating fewer calories than you burn with these weight loss plans.

french friesGlycemic Index

The glycemic index is a way to rate foods based on how easily they are broken down into sugars in your blood. The higher the glycemic index, the faster carbohydrates are turned into blood sugar. Higher blood sugar levels cause your body to release more insulin. This quick rise in insulin causes your body to overshoot and quickly lower your blood sugar to a level that is lower than normal. While this may not cause you to have a lot of symptoms, this might make you feel hungrier and eat more. 

Grill skewers with chicken and zucchiniTheoretically, high glycemic index foods can make you feel hungry after eating them, rather than feeling full. Also, most foods with a low glycemic index are higher in fiber. Some of the low carb diets restrict the amount on carbohydrates to 40% of your daily calories and focus more on the glycemic index of foods.


Early Weight Loss

Low carbohydrate diets tend to cause a quick early weight loss. When your body uses its own stored carbohydrates for energy, the chemical reaction produces water. This extra water then goes out in your urine. The ketosis state also causes your body to get rid of more water. Therefore, much of this early weight loss is just water weight.

If too many carbohydrates are added back, you can retain water and regain some of this water weight quickly. This can cause swelling. This effect is called refeeding edema.

How Well Do They Compared to Other Diets?

The studies on low carb diets lasted only up to one year. There is no scientific evidence at this time as to how well people do on different diets after one year. After six months, people generally lost more weight on low carb diets. After one year, the weight loss was about the same between low carb and low calorie diets.

One study looked specifically at the Atkins (very low carbohydrate), Zone (low carbohydrate), LEARN (low fat and high carbohydrate), and Ornish (very high carbohydrate) diets. It found that women on the Atkins diet lost more weight after one year than women on the other three diets, who all lost about the same amount of weight. It may be that people are able to stick to the low carb diets more easily than the other diets because the extra protein fills them up, which is probably why they are more successful at weight loss.

In that same study that compare the four different diets, women on the Atkins diet had better triglyceride and HDL (or good cholesterol) levels than those on the other diets. LDL (or bad cholesterol) levels were the same after one year with all of the diets. Blood pressure was also lower for women on the Atkins diet after one year compare to the other diets.

Another study lasting 2 years compared the Atkins diet, the Mediterranean diet, and a low-fat diet. It found that men lost the most weight with the Atkins diet (10.8 lbs) and almost as much weight with the Mediterranean diet plan (8.8 lbs). They only lost only 7.5 lbs on the low fat diet. Women in the study lost 5.3 lbs on the Atkins plan, 13.6 lbs on the Mediterranean, and only 0.22 lbs on the low-fat diet. It appears that Men do best on the low carb diets and women do best on the Mediterranean diet.

Risks

The current studies seem to indicate that low carbohydrate diets are safe. However, there are some theoretical risks to long term low carb dieting. They have a low fiber intake. Fiber can help reduce the risk of heart disease, stroke, and diabetes. In spite of this, low carb diets have been shown to improve cardiac risk factors, such as increasing HDL cholesterol and lowering triglycerides. They do this better than low-fat diets.

There is also a lower amount of magnesium, potassium, and vitamin C, as well as an increase in the loss of calcium with these diets. This may lead to osteoporosis. They are also low in thiamine, folate, and iron, as well as Vitamins A, B6, & E. You may need to take a vitamin supplement. Low carbohydrate diets raise the levels of a chemical called uric acid in the blood, which may worsen gout. The ketosis state can cause bad breath. You should discuss all of these things with your doctor.

Different Low-Carb Diets

The main low carbohydrate diets are the Atkins, South Beach, and Zone diets.

The Atkins diet focuses on low carbohydrate levels. The South Beach diet is more balanced and puts some limits on fat. The Zone diet focuses on eating the right ratio of carbohydrates to fat.

Return to Diets or the Home Page.

It is important you discuss any weight loss or exercise plan with your doctor. Only you and your physician can decide what is best for you. Some people have certain conditions that prevent them from doing all exercises, and goal body weights may be different for different people. You need to discuss all these things with your physician before starting any weight loss or exercise program.

This article was written by John Vickery, MD.

References

American Family Physician 2006;73:1942-8
Treatment Guidelines from The Medical Letter 2003;1:101
“Dietary therapy for obesity” Up To Date version 15.3
Journal of the American Medical Association 2007;297:969-977
“Prudent diet” Up To Date version 15.3
Treatment Guidelines from the Medical Letter 2008;6:23-28
N Engl J Med 2008;359:229-41

footer for Medical Weight Loss page

Site Build It!
Last updated 7/19/09