Glycemic load of promoted items at Subway and Burger King

Nutrition Research Newsletter, Nov, 2006

The glycemic index (GI) was first developed to guide dietary decisions for people with diabetes. The glycemic indexing of foods is an alternative method for ranking carbohydrate exchanges in foods based on their impact on blood glucose levels.

The Sydney University GI Research Service (SUGiRS) provides commercial GI testing for the Australian and international food industry. Food manufacturers contract with SUGiRS to have foods tested and are then allowed use of GI labeling in Australia and some other countries. Foods are tested in 10 healthy volunteers using standardized methods to assess the GI. Response to the food is compared with the blood glucose response to an equivalent carbohydrate amount of pure glucose or white bread as the reference food. Foods with a GI of 70 or more would be labeled as high, those with a GI of 55 to 70 are considered medium, and foods with a GI of 0 to 55 are considered low.

The potential role of the glycemic load (GL) of foods in metabolic dysregulation and the development of obesity is of increasing research interest. Several observational and intervention studies in children and adults have reported that a low-GI diet is associated with a lower body weight when compared to a reduced-fat diet. However, other observational studies have not found GI to be related to diabetes risk.

A recent study explored how GL may be applied to nutritionally promoted food items (low-fat, low carbohydrate, or low calorie). The evaluation is limited to Subway and Burger King chain restaurants, however such food options are being offered in an increasingly wider range of fast-food chains.

The menu items chosen for evaluation as well as the macronutrient content were selected from published menus from the restaurants. Options from the restaurants' menus were classified as such based on advertising of these foods under categories similar to low calories, low fat, or low carbohydrates on these franchises' Websites. The Original Whopper is used as the food item for comparison for Burger King, while the double meat turkey breast 6-inch sub and the cold cut trio 6-inch sub are used for Subway. The investigators also considered how the extras that were offered by the restaurant would alter the composition of the promoted products. Therefore, it was examined how adding a soft drink and either French fries (Burger King) or baked potato chips (Subway) would affect the overall content of the meal.

The GI of the menu items was obtained from published values. The GI contributed by each individual food item was calculated by taking the GI of the item and multiplying it by the proportion that the item contributed to the total carbohydrates. The GL was then determined by multiplying the GI by the amount of carbohydrate (grams) per serving for that item and then dividing by 100.

Subway offered seven low-fat (total/saturated fat: 3/5.5 g), low-calorie (230 to 330) sandwich options that had an average GL of 29. If the customer accepts the soda and baked potato chips, the total calories exceed 600 and the total/ saturated fat becomes 13/4 g, with a doubling of the GL. The Burger King low-fat options contained 4.5 g total fat and 1.5 g saturated fat, with GLs of 53 to 54, and low-calorie options (265 calories to 310 calories) had low GLs (0 to 18.3). Adding fries and a soda brings the GL up from a 53 for just the sandwich to 123 for the meal. The bunless low-carb Whopper has the same fat content (total/saturated: 42/13 g) as the original Whopper, but the GI and GL are zero.

The nutritional information provided for meal options at these two restaurants can help patients with diabetes make informed and good decisions. Adding the "extras" can dramatically increase fat, calories and the glycemic response. A. Bove, J. Hebreo, J. Wylie-Rosett, et al. Key Nutrients, Glycemic Index, and Glycemic Load of Nutritionally Promoted Items. The Diabetes Educator; 32:675-690 (September/October 2006). [Correspondence: Judith Wylie-Rosett, Altert Einstein College of Medicine, Jack and Pearl Resnick Campus, Department of Medicine (Endocrinology), 1300 Morris Park Avenue, Belfer Building, Room 1307, Bronx, NY 10461. E-mail: jwrosett@aecom.yu.edu.]