There are three basic macronutrients: protein, fat, and carbohydrate.  They are all some combination of carbon, hydrogen, and oxygen, with protein also containing nitrogen.  The particular molecular construction of each accounts for how it functions in the body.  For example, caloric content: Protein and carbohydrates contain 4 calories per gram, fat is 9 calories.  (Alcohol is 7 calories per gram.)  Caloric content is extremely important when it comes to planning a diet to stay in a negative caloric balance.  So along with making sure to ingest enough protein (at least 1 gram for every 2.2 pounds of lean body mass), bodybuilders need to exercise to burn up energy and limit their food and caloric intake sufficiently.

If you ingest more calories than you burn up, the body stores the excess as fat.  If you burn up more energy than you take in, your metabolism starts to turn stored fat into the necessary energy to make up the deficit.

All this is pretty basic knowledge.  But one aspect of diet many don’t understand is the role of the glycemic index.

Measuring a sandwich with a caliper
Glycemic index is a measure of how quickly various foods are digested. Shutterstock

The Glycemic index is a measure of how quickly various foods are digested.  Food with a low glycemic index metabolize fairly slowly, those with a high glycemic index metabolize more quickly – and enter the bloodstream as glucose, rapidly, causing the body to release insulin as a result. An excess of insulin is called an insulin spike.   

Insulin, a hormone produced by your pancreas, unlocks cells so that glucose can enter them. Without insulin, the glucose keeps floating around in your bloodstream with nowhere to go, becoming increasingly more concentrated over time.

When glucose builds up in your bloodstream, your blood glucose (blood sugar) levels rise. If they rise too much, this causes damage long-term to organs, nerves, and blood vessels. But in terms of diet, this also keeps your body from burning fat for energy and drives fat and sugar from your bloodstream into your fat cells.

All this makes your body think it’s starving, causing it to slow your metabolism and increase your hunger.

Bowl of steamed vegetables next to dumbbells and measuring tape
Caloric content is extremely important when it comes to planning a diet to stay in a negative caloric balance.a shutterstock

Recently, people have become more and more carbohydrate averse, believing that intake of carbs makes you gain fat.  But this view treats all carbs as equal, which they are not.  Back in the day, carbs were classified as simple or complex.  We have a more sophisticated view nowadays.  What was called simple carbs are now identified as those with a high glycemic index, meaning they enter the bloodstream quickly.  Complex carbs are now those with a low glycemic index, indicating they are digested more slowly and contribute to a slower increase in blood glucose.

Protein and fat foods have very low glycemic index ratings.  Carbs have higher glycemic index ratings, but different carb foods can be digested a lot faster or a lot slower.  For example, fructose (found in fruits) has an extremely high glycemic index.  Starches such as rice or potatoes have lower glycemic indexes.  If you want to eat low glycemic index carbs, go for green or yellow vegetables.

But the glycemic index is primarily a measure of how quickly foods are digested when they are in the stomach by themselves. For example, when you eat something on an empty stomach.  However, that is not how people usually eat.  We usually eat a variety of foods that are all in the stomach together.  When this is the case, the glycemic index of these foods is averaged out.  So, when you eat high-glycemic fruit with protein or fat already in your stomach, the digestion of the high-glycemic carbs is slowed down considerably and results in a much slower increase in blood glucose.

Seared meat with asparagus and tomatoes
We usually eat a variety of foods that are all in the stomach together.  When this is the case, the glycemic index of these foods is averaged out. Shutterstock

So, when you plan your diet, by all means, pay attention to the macronutrients and calories, eat enough protein and control your fat intake to reduce calories.  For carbohydrates, emphasize vegetables rather than starches.  And only eat high-glycemic foods like fruit or fruit juice when they will be combined with low glycemic food in the stomach.

For example, you can drink a glass of fruit juice after you have already eaten bacon and eggs without spiking your insulin level but drinking the juice on an empty stomach will likely cause an insulin spike.

In terms of macronutrients, all food that is not protein or fat is carbohydrate.  All carbohydrate is some kind of sugar, but there are various kinds of sugars. Some metabolize more quickly in the body than others.  The rate they do is called glycemic index – the measure of how rapidly food is converted into glycogen in the blood.  Fruit, containing fructose, has a very high glycemic index, starches lower and vegetables lower still.

There is a rating system for glycemic index.  Low-glycemic foods have a rating of 55 or less, and foods rated 70-100 are considered high-glycemic foods. Medium-level foods have a glycemic index of 56-69.

The measure of the glycemic index of food in your stomach is determined by an average of the GI of the different foods you are trying to digest.  When fat or protein is present, the GI of the stomach contents which contains some high-sugar content is lowered as a result.  So, it makes sense to eat high GI foods in combination with those with a lower GI.  For example, drinking orange juice for breakfast could be a problem because the sugar would spike your insulin level.  But this is not such a problem if you are also eating bacon and eggs, full of protein and fat.

In this era of “keto diets” carbohydrate has developed a negative reputation.  But carbs are an essential nutrient and an important part of a healthy diet.  You just have to keep in mind that all carbs are not created equal, some sugars metabolize more quickly and cause extreme insulin spikes, so attention needs to be paid to the glycemic index

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