Controlling Carbohydrates with a Low Glycemic Diet

by Douglas S. Kalman MS, RD

June, 26 2000

A recent study suggests that dietary fat may not be the principal cause of obesity (1). In fact, the battle is now becoming one of the types of carbohydrate that you eat may be the cause of weight gain and other related diseases. The researchers, led by David S. Ludwig, M.D., Ph.D., the Director of the Obesity Program at Children's Hospital in Boston, focused instead on glycemic index (GI), which is a measure of the effect foods have on blood glucose level after they are eaten.

Ludwig defines high-GI foods as those "that are rapidly digested and

absorbed or transformed metabolically into glucose." These include refined starchy foods (such as bread, cereal, rice, pasta, etc.) and table sugar. By contrast, low-GI foods comprise most vegetables, legumes, and fruits. To put it simply, high glycemic foods are ones that cause a rapid spike or

rise in your blood sugar values, while low glycemic foods rarely effect

blood sugar.

In this study of 12 obese adolescent males, the researchers found that

after eating high-GI meals, the subjects were hungrier and ate again

sooner: voluntary food intake was 53 percent greater than after a medium-GI meal, and 81 percent greater than after a low-GI meal. Apparently, eating a low glycemic diet can result in being less hungry and eating less throughout the day. The attached table, which lists the glycemic value of various foods, is a great tool in helping you to choose foods that promote a stable blood sugar and reduced appetite.

The researchers concluded that the hormonal and metabolic changes that

occurred in those who had eaten high-GI meals-as their bodies more readily absorbed glucose-led them to eat excessively. They also reported greater hunger sooner after eating than those who had eaten medium- and low-GI meals. The researchers acknowledge that the study charted only the acute effects of low-GI meals: "The effectiveness of a low-GI diet in promoting long-term weight loss is unknown." More studies are needed to determine the role of GI and other factors in eating and in weight gain. "Nevertheless," said Ludwig, "this study suggests possible advantages for treating obesity with a diet abundant in vegetables, legumes, and fruits; low in high-GI carbohydrates; and moderate in protein and fats." Ludwig also found that reducing GI in the diet improve serum lipids [cholesterol, triglyceride and high density lipoprotein (HDL)] while decreasing the risk of type 2 diabetes.

Recently, the concept of a body weight set point has been proposed. The set point theory basically states that body weight is predetermined and

extremely hard to alter. If you overeat the body responds by increasing the metabolic rate, when you undereat, the metabolism slows down. The body does this as a both a method to keep your weight where it wants it (thus, the set point theory) and as a protective mechanism (2). The link from the set point to the type of carbohydrate that you include in your diet is the glycemic effect of the carbohydrate. As previously stated, high glycemic carbohydrates (for the most part, unwanted in the diet) can increase hunger

and overall food intake throughout the day, whereas low glycemic

carbohydrates reduce appetite and enhance satiety. Thus, certain types of carbohydrates can increase the risk of obesity.

To further test how dietary carbohydrates effect physiology, researchers from Children's Hospital and Brigham and Women's Hospital in Boston tested

10 overweight men by putting them on two different reduced calorie diets and measuring the hormonal and weight response to the diets. The high glycemic diet was 67% carbohydrate, 15% protein and 18% fat, while the low glycemic diet consisted of 43% carbohydrate, 27% protein and 30% fat. Both

diets were the same in calories, while differing in macronutrient ratios and sources of carbohydrate (3).

The results of this study are nothing less than staggering. In fact, to all of those "high-carbo" fans out there, sorry but your diet leads to a slower metabolism, weight gain and leans towards a negative nitrogen balance.

Specifically, the high GI/high carbohydrate diet resulted in a decline in energy expenditure of 10.5%, while the low-GI/reduced carbohydrate diet only slowed the metabolic rate by 4.6%. It is important to point out that reduced calorie diets in general will slow the metabolism. The shocker in this study is the reduction of the metabolic rate on the high-GI diet was double that of the low-GI diet. Past research has not indicated that carbohydrate intake impacts nitrogen balance. Nitrogen balanceis related to protein intake and muscle mass status. When you follow a diet that is too restrictive in total calories, your body will pull upon protein in the muscles for energy. This is evident when looking at an anorexic or prisoner of war. The muscle wasting becomes apparent by the lack of tone on their body. This study demonstrated that a modest calorie reduction coupled with a high-GI diet results in a negative nitrogen balance - muscle protein being used for energy when compared to a low-GI diet (preserves lean body mass).

A popular diet that is slowly but surely receiving scientific validation is the Zone. In fact, if you examine the low-GI diet used in this study (43% carb, 27% protein, 30% fat), it is strikingly similar to the 40% carb, 30% protein and 30% fat put forth as optimal macronutrient ratios by Dr. Barry Sears. If you are looking to shed a few pounds, maintain lean body mass and keep your blood sugar in check, then a low-GI diet is for you. Table II contains a sample low-GI diet. Books such as the Zone or the Greenwich Diet can provide you with daily recipes, menus and a lifetime eating plan for a healthy, long, fit life.

Table 1.

Glycemic Value of Selected Foods.

This is an index that you can use to maximize your satiety, weight control and sugar cravings. In order to reach your full potential, it is better to pick a food with a score less than 60%. These foods should be a part of your daily eating plan, but may not have to be the sole entity of your energy consumption. In other words we want to control our insulin responses

to the sugar in our diet.

FOODGLYCEMIC INDEX (%)

All-Bran40

Fiber One49

Shredded Wheat67

Special K70

Sustain66

Cornflakes76

White Pasta50

Whole Wheat Pasta42

White Bread100

Grain Bread60

Brown Rice68

White Rice79

Eggs42

Cheese55

Beef21

Fish28

Chicken/Turkey40

Yams/Sweet Potato51

Peas/Legumes/Beans29-51

Potato70

Corn59

Apples50

Oranges39

Orange Juice46

Bananas79

Grapes74

Grapefruit26

Raisins62

Peaches29

Peanuts12

Popcorn62

Potato Chips52

Yogurt62

Skim Milk32

Whole Milk34

Jellybeans114

Croissants74

Cake56

Water Crackers102

Oatmeal Cookies74

Sponge Cake46

Table II.

Sample Low Glycemic Index Diet.

Breakfast

Omelet (made with 1 whole egg, 1 egg white, spinach, tomato and low fat

chedder cheese) Apple (with peel)

1 slice pumpernickel bread

1 tsp. Diet jelly

12 oz. Water

Lunch

Turkey breast sandwich ( whole grain 3-kernal bread, 4 oz. skinless turkey

breast, 1 tsp. mayonnaise, ¼ cup iceburg lettuce).

Tossed green salad (1 cup iceburg lettuce. ½ cup sliced celery, cucumber, 2

tsp. Italian dressing)

1 cup Stewed tomatoes

Apple (with peel)

8 oz. Sugar free gelatin

12 oz. water

Dinner

6 oz. Salmon fillet

1 cup String beans

½ cup Sweet red bell pepper

2 tsp. Butter

1 cup Tossed green salad ( ¾ cup iceburg lettuce, ½ cup sliced/diced

cucumber, tomato, 2 tsp. fat free French dressing)

1 slice pumpernickel bread

½ Grapefruit

12 oz. water

Sample Snacks (throughout the day, choose one)

Canned peaches in light syrup (1/2 cup)

2% cottage cheese (3/4 cup)

2% yogurt (1 cup)

2 Strips of string cheese