Sunday, July 5, 2009
As most people are probably aware, Americans are eating less fat, but are fatter than ever! One likely culprit is the fact that most people have re- placed fat with high GI foods such as “low fat” cookies, cakes, rice cakes and other high GI foods. Some research has even found the GI of food can actually alter the eating behavior all day long. A study in 1999, for example, examined how GI af- fected eating behavior in obese teenage boys. The boys consumed either a high, medium or low GI meal at breakfast and lunch. The researchers then measured how much the boys ate for a 5 hour period after lunch. Each of the meals contained the same number of calo- ries.
Amazingly, the study found food intake was 53 percent greater after the
medium GI meal, and a whopping 81 percent greater after the high GI
meal, when compared to the low GI meal.
As one would expect, insulin levels were dramatically higher after the high
GI meal. The study showed that a single high GI meal could a ect how
many calories a person will eat many hours later. The reason for this is most
likely the e ect of the high GI meal on blood sugar.
As mentioned, the study found the insulin levels of the high GI meal were
much higher than the other meals. When insulin rushes in to lower blood
sugar after a high GI meal, the result is low blood sugar shortly after. The
body senses the low blood sugar and responds by sending out the hunger
Eating low to moderate GI carbs throughout the day keeps steadier blood
sugar levels, so the body senses that adequate food and carbohydrates are
coming in. The feedback pathways controlling hunger and appetite (no
they are not the same thing) are incredibly complex and beyond the scope
of this chapter. Su ce it to say, blood sugar level and its e ect on insulin is
a key feedback mechanism the body uses to sense incoming nutrients, and
divert those nutrients where needed.
Numerous studies have found that the eating of high GI foods is associated
with greater body fat levels. Some animal studies have found that feeding
high GI foods to animals causes them to gain body fat. When you under-
stand the role of insulin in human metabolism, it does not take a Ph.D. in
biochemistry to see why this would happen.
One thing is clear, the GI of the carbs you eat will be a factor in how much
body fat is ultimately produced from the meal and the spike in insulin you
You know those low fat cakes you were so happy about? Throw ‘em out!
One important caveat to remember is that calories also matter and al-
though it may be possible to eat greater amounts of low GI carbs vs. high
GI carbs without problems, it’s far from a free-for-all excuse to stu oneself
The body can only burn or store so much carbohydrate as glycogen. Af-
ter that, increased body fat will be the result. The trick is to eat the cor-
rect amount – and types – of carbs to replenish glycogen levels and to fuel
workouts and daily activities, while making up the other calories in healthy
fats and proteins. How to do this will be covered in the following sections