Sunday, July 5, 2009
What are the drawbacks of the GI? For one thing, many people hold it up
as the Holy Grail of dieting, the be-all and end-all of nutrition. It’s not. It is
however another useful tool in the ght against body fat. Many things can
alter the GI of foods.
One drawback is that the GI is gured out in isolation - that is, each food
is tested alone to gure out its GI number. This makes perfect sense from
the research point of view, but rarely re ects how people really eat. Mixing
di erent foods together - the way most people actually eat - can have dra-
matic e ects on the GI of the food in question. Fat, ber, protein, cooking
times, etc. can all a ect the GI of a food or a meal, for that matter.
Want to lower the GI of a rice cake, for example? Smear a tablespoon of
peanut butter on it. The glycemic response to a meal can also be reduced
by vinegar, such as in a oil-and-vinegar salad dressing. Prolonged cooking
that increases starch gelatinization also increases the GI. Pasta cooked “al
dente” has a much lower GI than the same pasta cooked for 15 - 20 min-
In addition, the GI of a food sometimes gives an incomplete picture of its
impact on blood sugar. The GI value tells you how fast the carbohydrate in
a food is broken down into glucose, but it doesn’t tell you how much car-
bohydrate is present in a serving. This is why the concept of Glycemic Load
(GL) was developed. The GL of a food accounts for the amount of carbo-
hydrate present in a food. While the relationship between GI and GL holds
for most foods, there are some exceptions. A few foods can have a high GI,
but because they don’t contain a lot of carbohydrate in a typical serving,
the GL is reduced. Watermelon is a classic example, with a GI of 72 ( GI > 70
is considered high), but a GL of only 4, which is quite low.
GI is also misleading in the case of the simple sugar, fructose. Fructose has
a relatively low GI, but is quite lipogenic. Fructose consumption has been
positively linked to the worldwide epidemic of obesity. Fructose is found
in a wide variety of processed foods, and is also sold as an alternative “natu-
ral” sweetener - but it’s something to be avoided in larger amounts if you
want to limit fat gains, in spite of its low GI.
So, understanding the overall importance of the GI can be a useful tool in
getting the most out of a diet plan for gaining muscle with minimum body
fat, but it is far from the last word in nutrition. It’s important as part of the
“big picture,” but shouldn’t be the sole criterion used for including - or ex-
cluding - certain carb sources in your diet.