Carbohydrate selection and the insulin to glucagon ratio.

This post builds on the ground work set up in the How meal composition affects fat loss post. If you haven't read it, I strongly suggest reading it before you go one with this one.

Ok, let's do this. This time I want to talk about how and when you should eat your carbohydrates to stimulate the use of stored body fat for fuel.

The total amount of insulin secreted and the period of time insulin levels stay elevated after a meal is ingested depend on the amount and types of carbohydrates eaten.

Carbohydrate classification and the glycemic index.

Carbohydrates were conventionally classified structurally as simple or complex.
Simple carbohydrates are sugars known as monosaccharides. The term is usually used to describe refined sugars and white flour products. The natural simple carbohydrates are fructose (found in fruit) and lactose (found in dairy products).

Complex carbohydrates, also known as polysaccharides, are nothing more then multiple chain of simple sugars linked together.

This classic distinction leads toward the recommendation of complex carbohydrates over simple ones because nutritionists assumed that a long polysaccharide would take longer to digest than a simple sugar and therefore would lead to a more gradual and lasting blood glucose response with a smaller insulin response.

Although theoretically sound, this presumption is not true for many complex carbohydrates; some complex carbohydrates are digested more rapidly than simple sugars and cause drastic increases in insulin levels.

For this reason, the classic classification was dropped in favor of one that classifies carbohydrates according to how they are processed in the body – the glycemic index (GI).

The glycemic index, put simply, is a scale of how rapidly ingested carbohydrates enter the bloodstream as glucose. The speed at which ingested carbohydrates enter the bloodstream as glucose is one of the factors determining the insulin response.

Some scientists question the glycemic index’s accuracy at predicting the glycemic and insulin responses to mixed meals (protein, fats and various carbohydrates) because it only offers numbers for meals consisting only in a single carbohydrate eaten in a fixed quantity.

A JAMA (Journal of the American Medical Association) review on this subject has concluded that:

• Most refined starchy foods have a high GI whereas non starchy vegetables, fruits and legumes have a low GI.
• Eating protein and fats along with your carbohydrates lowers the GI of the individual carbohydrates somewhat but does not change the hierarchical relationship with regard to the GI.

What this means is that, despite initial concern, the GI can be used to predict with reasonable accuracy the glycemic response to mixed meals.

Optimizations to carbohydrate selection for maximum fat loss.

• Eat low to medium GI carbohydrates with every non post workout meal.
  This will reduce insulin spikes, improving the glucagon to insulin ratio.
  
  
• Include high GI carbohydrates only in your post workout meal.

Arguments in favor of a low GI diet instead of a high GI diet:

A study by Agus et al (2000) showed that during a short low calorie dieting period a low GI diet does a better job of preserving the metabolic rate and enhancing fat loss than a high GI diet.

A Ludwinget et al (2000) study showed that a 4 month period of low GI eating led to a decrease in body weight in overweight teens while a 4 month high GI eating period had the opposite effect leading to a increase in body weight in test subjects.

The same Ludwinget et al (2000) study associates low GI diets with
- better nutrition
- increased satiety/ decreased hunger
- fat loss