Effectiveness of a Low-Carbohydrate Diet for Obese Individuals With Type 2 Diabetes
The latest figures place nearly two-thirds of Americans in the overweight or ]]>obese]]> category, putting them at risk for numerous health conditions, including ]]>type 2 diabetes]]> . This suggests that the majority of Americans are—or should be—trying to lose weight. Along with exercise and behavior therapy, diet is a key component of any weight loss strategy. Just which diet is most effective, however, is the subject of ongoing debate.
Over the recent years much of the focus has been on the low-carbohydrate diet. Its popularity with consumers has compelled researchers to investigate its potential benefits and risks. So far the results look favorable for the low-carbohydrate diet—at least for the short term. Still, little is known about how low-carbohydrate diets cause weight loss or how they affect blood sugar control.
A new study in the March 15, 2005 edition of the Annals of Internal Medicine looked at the effects of a low-carbohydrate diet on obese individuals with type 2 diabetes. The study found that after following this diet for two weeks, participants lost an average of 3.6 pounds of body fat, voluntarily reduced their calorie intake by approximately 1,000 calories, and did not eat more fat or protein to make up for the lost carbohydrate calories.
About the Study
This study included 10 participants with type 2 diabetes and an average body mass index (BMI) of 40, classifying them as very obese. (A healthy BMI is between 19 and 25.) Participants resided at the research hospital throughout the three-week study, where they were allowed to maintain their usual activity level by walking around the hospital with a nurse, riding a stationary bike, doing calisthenics, or lifting weights.
The first phase of the study lasted one week. During this time participants continued their usual diet. Food was provided by the research center’s kitchen to meet participants’ requests and also included foods from local fast food restaurants. During the second phase, participants followed a very low-carbohydrate diet for two weeks. Total carbohydrate intake was reduced to approximately 21 grams per day, but participants were allowed an unrestricted amount of fat and protein.
The researchers weighed and recorded all foods that the participants consumed and obtained body weights, vital signs, blood tests, and urine outputs daily. They also assessed body composition and surveyed participants about diet satisfaction.
The participants’ body weight remained stable during the usual diet period. During the low-carbohydrate diet period, total body weight decreased by an average of 4.4 pounds and average body water decreased by 0.8 pounds. The researchers determined that body fat accounted for all 3.6 pounds of non-water weight.
During the usual diet period, participants consumed about the same number of calories as they burned, leading to energy balance and stable body weights. However, during the low-carbohydrate diet period, calorie expenditure exceeded calorie intake by an average of 1,027 calories. The average carbohydrate intake during the usual diet period was 309 grams, compared to just 21 grams during the low-carbohydrate phase.
Average fasting blood sugar levels decreased from 135 milligrams (mg) per deciliter (dL) (7.5 mmol/L) to 113 mg/dL (6.3 mmol/L) during the low-carbohydrate diet. Triglyceride levels decreased an average of 35%, and total cholesterol decreased an average of 10%. Low-density lipoprotein (LDL, or “bad”) and high-density lipoprotein (HDL, or “good”) cholesterol levels did not change. There was also no significant change in kidney function.
Participants rated the low-carbohydrate diet as comparable to their usual diet with respect to feelings of hunger, satisfaction, comfort, and energy levels.
How Does This Affect You?
This study adds to previous evidence showing that low-carbohydrate diets can promote weight loss. The method, however, is nothing new. As with any diet, a low-carbohydrate diet works because fewer calories are consumed than burned. The reason people consume fewer calories on the low-carbohydrate diet is that there are fewer foods to choose from—significantly fewer foods. In this study, participants chose from a selection of high protein, low-carbohydrate foods, including: chicken, turkey, beef, fish, and eggs (without any sauces or gravies); limited amounts of cheese; steamed or raw vegetables; diet gelatin; and certain Atkins brand products.
The findings that blood sugar and cholesterol levels improved with the low-carbohydrate diet are particularly important for people with type 2 diabetes, since for them, diet is not just about weight loss but also about blood sugar control. Additionally, this population has a higher risk of cardiovascular disease, making it important to keep cholesterol levels as low as possible. An original fear with the low-carbohydrate diet was that it would increase cholesterol levels since it includes a significant proportion of calories from animal fat. Apparently, this is not the case, at least not in the short-term.
Although the very low-carbohydrate diet works well for many individuals early on, there is some research suggesting that it may not be as effective over the long-term, mainly due to the difficulty of adhering to this type of limited diet for an extended period of time. Additionally, the long-term safety of a very low-carbohydrate is not yet known, and it may have different effects on cholesterol levels and kidney functioning.
If you are trying to lose weight, you need to find a way of eating fewer calories than you do now. A less extreme and probably safer version of the very low-carbohydrate diet is a low-carbohydrate diet that still includes healthy carbohydrates such as whole grains, fruit, and low-fat dairy products. Since most Americans currently consume a significant proportion of their calories from refined sugars such as white bread, cookies, and sweetened beverages, cutting out these types of products would go a long way to reducing calories, weight, and blood sugar levels.
American Diabetes Association
American Dietetic Association
Shape Up America
Boden G, Sargrad K, Homko C, Mazzoli M, Stein P. Effect of a low-carbohydrate diet on appetite, blood glucose levels, and insulin resistance in obese patients with type 2 diabetes. Annals of Internal Medicine . 2005; 142:403-411.
Bray G. Is there something special about low-carbohydrate diets? Annals of Internal Medicine . 2005; 142:469-470. [Editorial]
Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) (2002). National Academies Press. Available at: http://www.nap.edu/openbook/0309085373/html/207.html#pagetop . Accessed March 16, 2005.
Last reviewed Mar 18, 2005 by ]]>Richard Glickman-Simon, MD]]>
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