Building a lean, mean physique depends heavily on how you manage your body's natural production of insulin.
Just the right amount of this hormone is critical for allowing fat to be utilized for fuel while also maintaining the anabolic drive of nutrients into hungry muscles.
Dietary control of insulin maximizes muscle gains and promotes fat loss.
The macronutrient that influences insulin responses the most is carbohydrate. Due to their impact on insulin, your carb choices make or break your results from training.
Astute folks no longer think of carbs in terms of simple and complex. They understand the importance of low and high glycemic index (GI) carbohydrates. However, as I'll explain in this article, you can't live by one rule, the GI isn't perfect, it does come with a few problems. I'll show you how to overcome them
What is the GI?
The GI is a ranking of foods based on their immediate effect on blood glucose (blood sugar) levels. The GI ranks a food on a scale from 0 to 100 according to the extent to which it raises blood sugar levels after eating. Carbohydrate foods that break down quickly during digestion have the highest GI rating. Their blood sugar response is fast and high. The substance which produces the greatest rise in blood sugar is pure glucose. Therefore, the GI of glucose is 100.
Every other food is ranked between 100 and zero. Carbohydrates that break down slowly, releasing glucose gradually into the blood stream, have a low GI. Foods with a high GI produce a great surge of glucose into the blood stream. This surge in blood glucose is matched by another in insulin in an attempt to control blood glucose levels.
High GI foods produce marked fluctuations in blood glucose levels. Low GI foods, by virtue of their slow digestion and absorption, result in steady blood glucose and insulin levels.
By selecting carbs with the GI factor in mind, you will decrease the amount of insulin secreted while promote insulin sensitivity within tissues. Both factors enable fat to be utilized (burnt) for fuel while promoting a hormone profile maximizes muscle anabolism. The bottom line is a leaner, stronger, healthier physique.
Glycemic Load vs Glycemic Index
More recently, another term, the Glycemic Load (GL) has become popular when discussing the GI impact of food choices. Without trying to confuse you, both the GI and the GL are important but they are very different. A clear understanding of both terms will help you make much better choices at meal time to optimize the results from exercise.
Whereas GI compares the potential of foods containing the same quantity of carbohydrate to raise blood glucose, the amount of carbohydrate consumed also affects blood glucose levels and insulin responses.
The GI indicates how rapidly a particular food increases blood sugar levels after consumption, However, the GL takes into account the serving size of the food and the effect this has on blood glucose levels.
The GL is measured by the GI of a food multiplied by the carbohydrate content of the food (per 100grams). It provides a more accurate picture of blood sugar responses to meals.
The GL is useful to clarify the confusion about some foods on the GI list. That is, even though a food may technically have a high GI, it may not necessarily have a high GL.
Carrots and ice cream
For example, some very healthy foods such as carrots and watermelon have a rather high GI on most scales. However, that does not mean that these foods should be avoided if an individual is looking to optimize fat loss.
Plant foods such as carrots and watermelon may be listed with a fairly high GI, but they actually posses a low GL. This is due to the small amount of carbohydrate they contain per serving. According to Dr. Rob Thompson, author of The Glycemic Load Diet, you’d need to eat 30 carrots to get the same elevation in blood sugar as you’d get from one bagel.
Conversely, ice-cream is characteristically listed as a low GI food. However, the amount of calories contained per serving makes it an unrealistic staple food for anyone that wants to shed body fat and keep it off. A reflection of this is ice-cream’s high GL rating.
The GL describes the quality and quantity of carbohydrate in a meal or diet. The GL helps clarify carb choices as it reveals the real impact the meal will have on blood insulin responses. Knowing both the GI and GL will help you make much better carb choices to maximize results from training.
Dr Paul Cribb is an award-winning sports scientist, author, personal trainer and the creator of mp-body.com – the first ever science-based, research-proven, nationally accredited body transformation program. Learn more here.
References
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Fajcsak Z, Gabor A, Kovacs V, Marto. The effects of 6-week low glycemic load diet based on low glycemic index foods in overweight/obese children--pilot study. J Am Coll Nutr. (1):12-21, 2008.
Pereira MA. Dietary glycemic index and glycemic load in diabetes prevention-what can we learn from observational studies? Nat Clin Pract Endocrinol Metab. June 10, 2008