Why does the glycemic index of a carb NOT affect exercise performance?

Question

I read an article on SimplyShredded that claimed that the type of carbohydrate doesn't matter, but rather only the amount of carbs matter to bodybuilders. In the following excerpt, the author claims that exercise performance does not differ with carbs of differing glycemic index.

Nope, not even endurance exercise performance is affected by the GI of the food eaten before the training session. Neither do beta-endorphin levels, rate of perceived exertion, heart rate, ventilation, lactate, respiratory quotient and substrate oxidation rate. For anaerobic strength training, the GI of the carbs you eat makes absolutely zero difference in the gym. The whole ‘needing carbs for energy’ thinking is in your head anyway.

This seems to go against other books I've read and videos of pro bodybuilders I've watched. In these books and videos, they always say to eat low GI foods (yams, whole grain) throughout the day for stable energy levels and high GI foods (fruit, sugar) after working out for recovery and shifting to an anabolic state.

So who is right? Does the GI of a carb matter or not to bodybuilders?

Answer 1

More and more studies are coming up showing that your protein/carb/fat ratio and total calories are really the only thing that separates that shredded look from the flabby. That does not negate the need for intelligent self experimentation to find what works for you and your body.

Many anabolic diets work by manipulating the easiest hormone to manipulate: insulin. There are a couple that are more concerned with leptin such as LeanGains. The bottom line is that the deeper you dig into nutrition the less clear things become.

First, lets talk about exercise performance (per your question):

• Muscles are just as content to burn fat as they are glycogen
• Many people perform well in a fasted state, using only stored energy
• The key to exercise performance is what energy you have stored prior to training!

The question of low GI pre-training and high GI post-training has to do with manipulating the insulin response. The general idea is to remain in a fat burning state as long as possible, and then replenish the energy after training as quickly as possible. It's the same idea with protein manufacturers trying to give you the quickest absorbing protein--which isn't always what you want.

• From an energy standpoint, you simply want to replenish your glycogen stores.
• The speed of replenishment doesn't affect your training performance, just that it's replenished.
• Your hormone response is regulated by the nervous system, and it will respond as fast or slow as you are genetically wired.

I don't have any links, but the real main issue seems to be that many of the claims for anabolic diets and thermal effect of food are overstated. Those effects are present, but not to a point where they become game changers. That doesn't mean they are not useful tools. People respond differently to the proportions of food that they eat. The key is finding the right balance and approach that works for you both with your body and your schedule.