It is not how much a food raises insulin, as too many sources have erroneously reported. No, instead it is based on how much blood glucose rises after consuming a particular food over a 2-hour period. This is compared to a "reference" food usually glucose or white bread.
For instance, if you consume 50 grams of glucose (that'll make you swear off candy for a month or two), you'll get a fairly dramatic elevation in blood glucose. Let's say you consume 50 grams of carbs found in the form of apples. Your blood glucose would probably rise only 40% as high as compared to glucose. So the GI rating for apples would be 40. Get it?
Why The GI Rating Is Important In A Nutshell
Scientists have compared the effects of four different meals (low to high GI rating) each containing 1 gram of carbs per kg. body weight, fed 1-hour before cycling to exhaustion (65-70% of V02max). The meals were boiled lentils (low GI rating = 29), baked potato (high GI rating = 98), glucose (high GI rating = 100) and water (no GI rating).
Blood glucose declined considerably in the potato and glucose group right at the start of exercise. Also, the lentil group burned more fat during exercise than the glucose or potato groups. And last, but not least, the lentil-fed groups lasted longer on the bike test than the other groups .
In a similar study, women who consumed a moderate glycemic food (75 g of sweetened whole grain rolled oats with 7 g fiber) 45 minutes before an exercise test performed longer on a bike test to exhaustion than when they consumed a high glycemic food (sweetened whole-oat flour with 3 g fiber). In fact they lasted 16% longer !
Our conclusion? If you were going to eat a meal or take a supplement prior to training, it would make sense to skip the high GI foods and stick with the low GI foods. Of course there will be those individuals in whom the GI of the food has little to no effect on how they train or work out. But why take the risk?
Low GI, Low Body Fat
By now you should know that even though Americans eat less and less fat, they keep getting fatter! What gives? Well, they have in all likelihood "replaced" fat consumption with sugars as well as exercising less. It's not from overeating apples, vegetables or proteins like MET-Rx, that's for sure.
Indeed, it's probably high GI cookies, cakes, and assorted junk you'll find in the crap aisle of your local grocer.
Fat Kids Can Become Fat Adults
An interesting study from the Journal Of Pediatrics looked at how the GI affected eating behavior in obese teenage boys . First the subjects consumed a high, medium or low GI meal at breakfast and lunch. The researchers then measured how much these chubbies ate for the 5-hour period after lunch. Researchers found that voluntary food intake was 53% greater after the medium GI meal and a whopping 81% greater after the high GI meal, when compared to the low GI meal. Also, insulin levels were dramatically higher after the high GI meal. So even though each meal had the same number of calories, it's clear that the impact on how you eat later is dramatically different!
A study from the University of Sydney (Australia) found that "the hypersecretion of insulin without insulin resistance may be one mechanism for increased fat deposition in rats fed a high GI diets ." And scientists from the University of Navarra (Spain) found that "after intake of the high-carbohydrate meal, the overweight men had high insulin, higher fatty acid and triglyceride concentrations than did the lean men ."
Now don't think you have an unlimited metabolism with a license to pig-out endlessly on low GI foods. Eating too much of anything may make you rounder than the Fuji blimp. But if given a choice, choose the low GI foods. In the long run, you will probably end up eating just a little less afterwards.
Eat Low Glycemic For A Healthy Heart
Though having a healthy heart and being disease-free is not a concern for most bodybuilders, let's face it, we're all getting older and our hearts are not getting any cleaner. Eating high glycemic foods can by itself increase your risk of coronary heart disease. In fact, carbohydrates classified by their glycemic index rather than as either simple or complex, were a better predictor of coronary heart disease . Though this study examined women only, it is a good possibility that similar results would be found in men.
Moral Of The Story:
- Eating low GI foods 30-60 minutes before exercise minimizes the hypoglycemia that might occur at the start of exercise.
- Eating low GI foods prior to exercise may increase the amount of free fatty acids in the blood therefore increasing fat oxidation.
- Eating low GI foods will result in less eating later, greater appetite suppression, and perhaps fewer cravings for quick-n- easy junk foods.
- Eating low GI foods is healthier for you metabolically (insulin levels are stable) and cardiovascularly (decreased risk of heart disease).
- Eating low GI foods may promote lower body fat levels and leaner, muscular physique.
PLANET MUSCLE NOTE: The popular, high-quality supplement company Worldwide Sport Nutrition is considered the pioneer in low glycemic products in our industry, with revolutionary products such as the Pure Protein Bar and the Ultra Pure Protein Shake. Their new division, Low Glycemic Technologies, specializes in low GI supplements such as the Revolution Bar and Revolution Shake. Other up-to-date companies have lagged but are now struggling to fall in line. You can find Worldwide Sport Nutrition and the Low Glycemic Technology products at Bodybuilding.com.
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