Move over low carbohydrate, here comes the next craze -- the glycemic index. As attention to the Atkins and South Beach diets wanes, watch out for the next wave of diet books featuring the glycemic index. Indeed, just googling the term shows a variety of books already exist that promise health benefits, including type 2 diabetes control and the ever elusive weight loss miracle.
Just how does the glycemic index work? Should we add another diet book to our already burgeoning libraries?
The Glycemic Index Promise for Diabetes & Weight Loss
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The glycemic index is simply a measure of the effect a carbohydrate-containing food has on blood sugar levels. The theory - emphasis on theory; this isn't proven -- is that foods with a higher glycemic index cause blood sugar levels to rise more than foods with a lower index, thereby increasing insulin secretion, which then causes blood sugar levels to drop. Theoretically, that leads to false hunger, causing us to eat more than our body really needs. Hence, struggles with weight and, for people with diabetes, blood sugar control.
A number of studies have looked at various aspects of this promise. For people with diabetes, several studies do suggest that paying attention to the glycemic impact of foods may have a positive effect on A1C levels (a measure of blood sugar control). Studies of the effect of the glycemic index on weight gain are inconsistent; some show a potential effect; others don't. A recent study of 32 healthy 'overweight' adults with normal glucose tolerance, however, showed that those who had high levels of insulin secretion and ate a low glycemic load diet lost the most weight.
The Problems with Using the Glycemic Index for Weight Loss &/or Diabetes Control
The glycemic index, however, has a number of practical problems. For one, it fails to truly categorize foods according to their impact on glycemic effect because it doesn't consider the amount of a food that we tend to eat at one time. A good example of this is a carrot versus a Snickers bar.
In the low carbohydrate diet craze, carrots gained a bad reputation due to their glycemic index. They rank 92 on the scale, which runs from 0 to 100. By comparison, a Snickers bar has a glycemic index of only 68. So does that mean Snickers are better choices than carrots for type 2 diabetes and weight loss? No. Because the amount of carbohydrate eaten at any one time is an important factor. If you take into account how much carbohydrate you eat in each carrot vs. each Snickers bar - which is the basis for a calculation called glycemic load - carrots rank as 7 and Snickers as 23. To get as much carbohydrate from carrots as one Snickers bar, we'd have to eat about 8 carrots in one sitting.
The concept of glycemic load, then, appears to better to assess the effect of individual foods on blood sugar levels. Still, experts agree that this concept has more utility for research on how populations of people eat, not for individual diet planning. One reason is because glycemic load is based on measures of the glycemic index, and the measures themselves are highly variable according to, among other things, individual response, where a food is grown, how ripe it is, its physical form (whether it's whole or ground, for example) and how it is prepared.
For example, rice from Italy has a glycemic index of 102; in Canada, it's 72. Tables of glycemic index often reflect an average glycemic index, which can be useful for studies of what an entire population eats. When it gets down to individuals, obviously the variations can make a big difference. To further complicate things, fat and protein also affect the glycemic response, resulting in a lower glycemic effect when a food is eaten in combination with other foods rather than by itself.
What to Do
Clearly, trying to determine the effect of a food on blood sugar outside of a laboratory is fraught with complications that would make eating a low glycemic diet an exercise in frustration. That is, if you keep looking at single foods. But if you look at the total diet, there are some words of wisdom to make smart eating a reality.
Choose among a wide variety of whole foods, including whole grains, beans, vegetables, fruits, lowfat dairy products and protein foods. Most likely, you'll automatically be eating a lower glycemic diet as a result. Refined foods - those with fiber removed such as white bread and fruit juices - tend to have a higher glycemic load. What's more, they're lower in all the vitamins, minerals, phytonutrients and other substances that make for healthy eating.
If you do want to eat a food with a higher glycemic index, eat it in combination with a protein food. For example, saltines with peanut butter for a snack.
If you have type 1 or type 2 diabetes or high insulin levels, work with your dietitian to determine if some foods have a higher glycemic effect for you. This may involve checking your blood sugar levels after test meals.
So save your money - skip the latest book promising easy solutions for type 2 diabetes and weight loss by using the glycemic index. First, it isn't easy; second, it's not necessarily accurate. Try spending your money instead on something that really helps you feel better - like a massage, facial, manicure, pedicure, personal training session, and the like.
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