I always try to encourage my patients to eat healthy and only as much as their bodies need. However, it is just as important to understand why some foods are better than others to eat.

One key point to consider when deciding what or how much of a particular food to eat is its glycemic index (GI).

A food with a low glycemic index has less carbohydrates in it, is digested more slowly and typically raises blood sugar (glucose) levels only moderately. A food with a high GI contains a lot more carbohydrates and is digested quickly, resulting in blood sugar (glucose) levels increasing quickly and more than desired.

The presence of glucose in the bloodstream usually triggers the production of insulin, a hormone that helps glucose get into cells where it can be used for energy.

Once the cells in our bodies have enough stores of glucose, any extra glucose still remaining in the bloodstream can be stored in our muscles and liver for later use.

If our muscle and liver stores of glucose are full, but we still have extra glucose floating around in our blood, then insulin can help our body store this excess sugar as fat. Yes, as fat. This means that any excess sugar in your blood is converted to and stored as fat in your fat cells.

Since insulin helps glucose get into cells where energy is made, insulin is vital to fuelling the body. However, too much insulin secretion, due to consuming too many carbohydrates or sugar over long periods of time can cause serious health problems.

Prolonged exposure to elevated levels of insulin can cause:

• High triglycerides

• High “bad” LDL cholesterol

• Low “good” HDL cholesterol

• High blood pressure

• Insulin resistance

• Increased appetite

• Obesity

• Risk of developing or exacerbating Type 2 diabetes.

The presence of these unhealthy factors raises a person’s risk of cardiovascular disease, diabetes, and prostate or breast cancer. For example, studies published in the American Journal of Clinical Nutrition in 2002 found diets high in carbohydrates that also have a high GI were linked to a greater risk of coronary heart disease.

Other studies have also shown that people who eat foods with a high GI daily increase their risk of developing chronic conditions such as cardiovascular disease, Type 2 diabetes and certain cancers.

An article appearing in the October 2003 issue of Critical Reviews in Food Science and Nutrition by doctors Stacey Bell and Barry Sears explains in detail what happens metabolically when a high glycemic load meal or snack is eaten.

In their study of healthy volunteers, Bell and Sears found that two hours after eating a high glycemic meal, blood sugar levels were twice as high as the levels that resulted from consumption of a low glycemic meal. These high blood sugar levels triggered the synthesis and release of insulin, our key hormone for getting sugar back out of the bloodstream and into the cells.

While a single, high GI meal might not cause significant health problems for our bodies, frequent consumption of high glycemic load meals can result in perpetually high insulin levels.

When insulin levels stay high, our hormone (endocrine) system can start out on a rollercoaster ride in which the body tries to adjust to its perpetually high insulin level with changes in other hormone levels that can leave us tired, hungry, and on a course toward increased risk of cardiovascular disease and Type 2 diabetes.

By contrast, many or all of these unfavourable hormonal shifts become less likely when a meal with low GI is eaten.

Since low glycemic meals take longer to digest and absorb, and nutrients are released gradually, blood sugar levels tend to remain more stable and insulin levels tend to rise in a non-risky fashion. As an added benefit, a low glycemic way of eating is associated with lower levels of LDL (bad) cholesterol and triglycerides.

Have you ever noticed that you feel lethargic after eating foods that stimulate a large insulin response, such as donuts or candy? This often happens because too much insulin is produced in response to such foods, and this excess insulin causes blood sugar levels to drop below normal, resulting in low blood sugar (hypoglycemia) and fatigue.

When this happens, people who are unaware that the high-sugar food they just ate is the reason for their sudden drop in energy reach for another sweet or high carbohydrate food, which starts the cycle all over again.

When our blood sugar is bouncing from too high to too low repeatedly throughout the day, we certainly don’t feel our best.

On the other hand, when our food choices help us maintain consistent normal blood sugar levels, we feel great and have the energy we need to enjoy long, active days.