Nutrition Pearls: Glycemic Load Diets
James is a 38-year-old man who is clinically overweight but otherwise healthy. He is looking to improve his diet and wants to know whether dried fruit is a snack he should add to his weekly menu.
He is concerned that dried fruit may not be as healthy as its fresh counterpart.
How would you advise your patient?
What is the correct answer?
(Answer and discussion on next page)
Dr. Gourmet is the definitive health and nutrition web resource for both physicians and patients with evidence-based resources include special diets for coumadin users, patients with GERD/acid reflux, celiac disease, type 2 diabetes, low sodium diets (1500 mg/d), and lactose intolerance.
Timothy S. Harlan, MD, is a board-certified internist and professional chef who translates the Mediterranean diet for the American kitchen with familiar, healthy recipes. He is an assistant dean for clinical services, executive director of The Goldring Center for Culinary Medicine, and associate professor of medicine at Tulane University in New Orleans. Dr Harlan was the 2014 co-chair and keynote speaker at the recent Cardiometabolic Risk Summit in Las Vegas.
Now, for the first time, Dr. Gourmet is sharing nutritional pearls of wisdom with the Consultant360 audience. Sign up today to receive an update from the literature each week.
Answer: A high-glycemic load diet may help maintain weight loss.
I am personally always interested in examples of how research can set out to learn one thing and discover something completely different along the way.
Scientists are often investigating the role of self-efficacy in weight management. Self-efficacy is defined as the feeling that one is competent or capable of performing a task. Researchers at Tufts University decided to investigate whether counseling intended to lead to greater self-efficacy, combined with a high or low glycemic load (high-GL or low-GL) diet, would help individuals lose or maintain weight loss.
What is the Glycemic Load?
GL is based on the glycemic index—a standardized measure that calculates how much a food will raise one’s blood sugar levels after consumption. GL is a more practical application of the glycemic index; it is calculated based on the glycemic index of a food as well as the amount of available carbohydrates contained in that food. Therefore, GL can be calculated for different sizes of servings of food, an entire meal, or everything that an individual consumes in a day.
___________________________________________________________________________________________________________________________________________________________________________
RELATED CONTENT
How Do Diets With A Low Glycemic Index Impact Cardiovascular Risk
Fact or Fiction: The Truth About Special Diets
___________________________________________________________________________________________________________________________________________________________________________
The Research
For this study, 42 clinically overweight but otherwise healthy men and women (aged 20-42) received twice-weekly counseling sessions intended to lead to greater feelings of self-efficacy around weight loss. They were simultaneously randomly assigned to a high-GL or a low-GL diet.
For the first 6 months of the study, all food was provided to the participants. For the last 6 months, the participants planned, shopped for, and cooked their own meals according to training they’d been given on their respective diets and the number of calories they were assigned to eat.
The Results
Both groups lost about the same amount of weight, and the GL level of their diets did not appear to affect the participants’ levels of self-efficacy.
Almost as an aside, the researchers note that those on a low-GL diet regained some weight during the second 6 months of the study, while those on a high-GL diet maintained their initial weight loss. This suggests that a high-GL diet is more sustainable.
Cardiometabolic Risk Summit Follow-Up
At the 2014 Cardiometabolic Risk Summit I was asked that, since the DASH diet lists raisins and other dehydrated fruits as fruits, are these considered high-glycemic and high-calorie foods?
My response: Dehydrated fruit will always be higher in calories by weight. This is simply because of the water lost when the fruit is dried, not because the amount of sugar or fiber in the fruit changes.
Let’s take the average raw apricot. The USDA Nutrient Database reports that it weighs 35 g and contains 30.22 g of water. That means the nutrients in the apricot (the non-water part of the fruit) weighs 4.78 g.
The USDA reports that a half of a dried apricot weighs 3.5 g (or 7 g for a whole apricot on average). Of that, 1.08 g is water. When you do the math, a whole dried apricot (without the water) is 4.84 g [(2 x 7) - (2 x 1.08)]. In essence, the dried and the fresh apricot contain the same amount of fruit when you exclude the weight of the water.
When you look at the number of calories in the whole dried apricot versus the fresh apricot they are exactly the same: 17 calories. They have about the same amount of sugar and the same amount of fiber. That is because they are really the same fruit—only the fresh apricot has more water.
I am not a big believer that the glycemic index is anything other than an interesting scientific oddity. In the case of apricots, the University of Sidney website reports 2 values for raw apricots: 34 and 57. It also reports 5 values for dried apricots: 30, 31, 32, 32, and 42. Why is there such variation? The glycemic index is wildly unreliable. In some cases, they rely on as few as 7 subjects in their testing and there is wide variation in the results because of this small sample size.
Take another example: The University of Syndey website notes that the glycemic index value of a Dove dark chocolate is 23. Since that is lower than the apricots, does that mean Dove dark chocolate is better for you than an apricot? Glycemic index is interesting, but is science in search of a practical application.
The real risk for caloric consumption in dried versus fresh fruit is not that there is a difference in the nutrient content between a dried or fresh apricot. It is that there is more volume in the fresh, and as such, it may take longer to eat. One might end up consuming more dried apricots than fresh as a result (emphasis on the might). Either way, you can consume as much fruit as you want.
What’s the “Take Home”?
In the end, counseling patients about glycemic index or glycemic load will only mislead them. We eat fruit, not numbers, and counseling patients about great quality food is the key. Tell your patients to eat either dried or fresh fruit as a snack. At 17 calories, they would have to eat about 13 apricots (dried or fresh) to equal a Dove dark chocolate bar. Both taste great, but they will like the apricots just as much in the long run and be healthier for it.
Reference:
1. Macht M, Dettmer D. Everyday mood and emotions after eating a chocolate bar or an apple. Appetite. 2006;46(3):332-336.