Definition of Carbohydrates

This definition of carbohydrates will give you a better understanding of what are carbohydrates, what are complex carbohydrates and what are simple carbs? You can then use this information for your own weight loss efforts.

Carbohydrate is one of the body's main sources of fuel (the other being fat) and it should constitute around 30-40% of your total calorie intake each day if you want to lose weight.

Carbohydrate is composed of three elements, carbon, hydrogen and oxygen and each gram of carbohydrate yields 4 calories or 16 kilojoules of energy.

Carbohydrate is the only source of fuel used by the brain and nerve tissue under normal circumstances as well as being the primary source of fuel for working muscles during intense exercise, e.g. weight training. The body also uses it during the absorption phase following a meal.

Definition of Carbohydrates: Classification and Composition

There are two main types of carbohydrates: simple carbs and complex carbs. Simple carbohydrates (sugars) may be found in food as single molecules (monosaccharides) or as two molecules bonded together (disaccharides).

The image featured here is the chemical structure of a glucose molecule.

There are three types of monosaccharides: glucose, galactose and fructose and these combine to form the disaccharides.

For example:

glucose-glucose forms maltose;
galactose-galactose forms lactose;
glucose-fructose forms sucrose.

Complex carbohydrates (polysaccharides) on the other hand, contain three or more glucose molecules bonded together.

For example:

glucose-glucose-glucose-glucose

It is important to note that glucose is the only type of carbohydrate used by the body. Therefore, if other types of carbohydrates are consumed, they must be broken down by digestive enzymes and/ or converted into glucose by the liver first before they can be used by the body.

There are different digestive enzymes throughout the gastrointestinal tract.

The saliva contains ptyalin (salivary amylase), which breaks down complex carbohydrates into disacchardies (two molecule sugars).

Then, when food enter the stomach hydrochloric acid (HCl) gets produced by the stomach cells. This then stimulates other stomach cells to produce gastric protease, which is an enzyme that breaks down proteins.

Depending on the size and make up of the meal consumed, food can stay in the stomach for several hours. From here it goes (as a liquid called chyme) into the first part of the small intestine, which is called the duodenum.

It is here that enzymes from the pancreas further digest the food consumed. All 3 macronutrients are digested here. These enzymes are: pancreatic protease, pancreatic amylase and pancreatic lipase. The pancreas also produces sodium bicarbonate (NaHCO3), which neutralises the acid coming from the stomach.

The second part of the small intestine (jejunum) is where further digestion occurs along with some absorption. All the 3 macronutrients are digested here and there are specific enzymes being produced for the disacchardies to break them into monosaccharides. The enzymes are lactase (breaks down lactose), maltase (breaks down maltose) and sucrase (breaks down sucrose).

In the third part of the small intestine (ileum) is where a small amount of digestion occurs with mainly absorption.

To get a more detailed definition of carbohydrates, what are carbohydrates, what are complex carbohydrates and simple carbs as well as how the body digests carbohydrates, and how you can manipulate carbohydrates to help you lose weight, get a copy of the my e-book, Look Good Feel Great!

Click here to find out your Daily Carbohydrate Intake

Click here to get some examples of carbohydrates

Click here to go to the Low Carb Food List

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