Basic Guide to Carbohydrates

We’re all a bit carb obsessed lately what with the influx of low carb, controlled carb, carb cycling diets that have dominated the nutrition and health scene.  Before you jump on the latest carb wagon it’s wise to take some time to learn about carbohydrates as a group of macronutrients and how they are processed by our body.  This will help you determine your needs and possibly the food choices you subsequently make regarding carbohydrates. Here at Fitter Food we have simplified the science to help you out.

The human diet consists of macronutrients; substances we consume to provide our body with energy.  These are measured in units known as calories.  There are four different types of macronutrient and each offers differing amounts of calories per gram: 

  • Protein 4 calories per gram
  • Carbohydrate 4 calories per gram
  • Fat 9 calories per gram
  • Alcohol 7 calories per gram

In this article we’re going to focus on carbohydrates.  In biochemistry carbohydrates are referred to as saccharides, which comes from the Greek word sákkharon meaning “sugar.” We commonly divide carbohydrates into four chemical groups:

  1. Monosaccharides
  2. Disaccharides
  3. Oligosaccharides
  4. Polysaccharides

Take a moment to consider the name of each and you can clearly see the name is based on the number of saccharide molecules it contains.

Monosaccharides & Disaccharides

These have only 1 or 2 sugar molecules and are therefore known as simple forms of carbohydrates. These occur naturally in foods including fruit, vegetables and dairy.  All carbohydrates when digested are broken down into single molecules of sugar, either glucose, fructose or galactose. 


Blood SugarGlucose is a single sugar molecule or monosaccaride.  It is the body’s preferred energy source and so when you consume more complex carbohydrates they are digested and broken down into single units of glucose.  These circulate in the blood (known as blood sugar) and when blood levels of glucose rise our body secretes the hormone insulin.

Insulin helps to shuttle the glucose into our cells to be used as energy for thousands of metabolic processes or it may be stored in muscle cells or the liver as something known as ‘glycogen’ This stored energy or glycogen can be released when we need a source of energy quickly. Hitting the wall in a marathon is the term used when your body has utilised all the glucose available in the blood and all the stored glycogen in the muscles and liver.  It hurts (apparently!)


Fruit 3Fructose is the sugar found naturally in many fruits and vegetables, and also added to various soft drinks and snacks or confectionary. It is distinct from other sugars because it has a very different metabolic pathway.  Fructose is processed in the liver and relies on an enzyme known as fructokinase to break it down.

It is not the preferred energy source for muscles or the brain (they run on glucose) and so has more lipogenic (fat producing) properties and may cause weight gain in some people, especially if taken in excess. Unlike glucose it doesn’t cause insulin to be released, and studies have shown it can potentially interfere with the leptin signalling, a hormone involved in appetite regulation, energy intake and expenditure. This isn’t so much of an issue if you’re just eating a few pieces of fruit but some processed foods and drinks contain excessively high amounts of fructose.


2014-07-29 13.35.10This is the natural sugar found in milk and therefore other dairy produce.  It is not well tolerated by most people. Our pancreas produces an enzyme known as lactase to breakdown lactose into smaller units of sugar: glucose and galactose.  However, we stop producing this after the age of two, leading some health practitioners to suggest that maybe we’re not really supposed to drink milk after childhood.  Although nothing about the human body ever seems to be straight forward and the deal with dairy is no exception as something known as “lactase persistence” has been observed in some populations, whereby genetic adaptations are taking place and we continue to produce lactase enzymes into adulthood.   You can be tested to see if you have the gene code for lactase persistence via DNA Diet.  We’ve been tested and sadly don’t have it, however, that doesn’t stop Matt eating ice cream.  


This is what most of us would recognise as sugar if asked.  Obtained from sugar cane or beets and commonly referred to as ‘table sugar.’ Fruits and vegetables also naturally contain sucrose. When sucrose is consumed, digestive enzymes separate sucrose into glucose and fructose. The body will use glucose as its main energy source and the excess energy from fructose, if not used, could lead to weight gain.   


This name originates from the Greek word oligos meaning  ‘few’ so it’s literally a few simple sugars linked together.  

Fructo-oligosaccharides (FOS) is found in many vegetables and consists of small chains of fructose molecules. Galactooligosaccharides (GOS) consist of short chains of galactose molecules. 

Oligosaccharides are broken down during digestion into their single molecules of either glucose, fructose or galactose, however,  a portion is left undigested and provides food for our gut bacteria.  Research is suggesting that increasing consumption of oligosaccarides can boost the number of beneficial bacteria in the colon and suppress populations of harmful bacteria.

Foods such as Jerusalem artichoke, burdock, chicory, leeks, onions, and asparagus are a good source of FOS and GOS is naturally found in soybeans or can be produced from lactose (milk sugar). 


Sweet 'tato wedgesAs the name suggests these consists of many sugar molecules bonded together and occur naturally in vegetables, grains and pulses. Commonly referred to as starch. Fibre also is also classified as a complex carbohydrate. 

Starch is the most common carbohydrate in the human diet. Major sources include cereal grains (rice, wheat, and maize) root vegetables, sweet potatoes, rye, chestnuts and legumes (lentils, peas, chickpeas, and mung beans).

Starch is made up of two molecules; amylose and amylopectin. Amylose consists of hundreds or even thousands of glucose molecules closely interlinked, it takes our digestive system a while to break it down and therefore is digested slowly.  If our hormones are functioning effectively amylose supports good blood sugar balance because as it’s slow release of glucose molecules does not cause a large spike in blood sugar levels. Around 20- 30 % of the natural starch in plant foods is made up of amylose.

Amylopectin is much larger and consists of millions of glucose molecules, and these are easily broken down during the digestive process. Once digested the result is a big rush of sugar into the blood which can spike your blood sugar rapidly and will be followed by a sudden drop that leaves you hungry: hungry and angry! About 70 to 80 percent of the total natural starch in plants is made up of amylopectin.

Once consumed these are broken down into single units of glucose and this actually starts when we chew food.  Our saliva has an amylase enzyme that begins breaking down carbohydrates as soon as we start chomping. When determining whether a source of starch has a healthily impact upon blood glucose levels we always advise testing with a glucose monitor.

Consuming starch based carbohydrates with them with fat which will slow down the relase of the glucose into the bloodstream, so never skip the butter on your baked potato.  Alternatively you can choose fibre rich sources such as brown rice, potatoes and root vegetables.  These will then be broken down at slower rate and provide a more sustained release of energy. We still recommend glucose testing to establish your carbohydrate tolerance where possible. 

Resistant Starch

Another type of starch that recently received a great deal of focus by the Paleo community, referred to as resistant starch as it literally ‘resists’ digestion and instead is fermented in the large intestine feeding the growth of good bacteria.  Excitingly it’s also been shown to improve blood sugar balance and detoxification as the resistant starch binds to bad bugs in the gut and toxins and carries them out the body.  It also improves bowel regularity so definitely increase your consumption if constipation is an issue for you.  White potatoes, white rice and legumes provide excellent sources of resistant starch. The important thing to remember is that the resistant starch is formed once the starch has been cooked and cooled.  An easy way to implement is to cook extra rice or potatoes for dinner and have some cold potato or rice salad for lunch the following day.

For more information pick up a copy of our debut book: Fitter Food – A Life Long Recipe for Health and Fat Loss.