What are Carbohydrates, Simple carbs and Complex Carbs

a pan with white potatoes

What are Carbohydrates?

Carbohydrates (Carbs) are one of the 3 main macronutrients whose primary purpose is to provide the body with energy, and consist of carbon, hydrogen and oxygen atoms. Carbs can be found in different forms; starchy carbs, fibres and simple sugars found in fruits, dairy products, grains and vegetables. However when digested these take the form of glucose, scientifically known as sugar molecules.

The brain alone requires a constant supply of approximately 100-120g of glucose to function normally! However luckily, your body can make this amount without any consumption of carbs (hence why you can still function on a low carb/ketogenic diet).

All carbohydrates can be classified into simple carbs or complex carbs:

What are simple carbs?

These refer to the sugars found in foods, such as fructose (found in fruit) and galactose (found in milk). These simple carbs consist of approximately 1-10 sugar units each, also known as monosaccharides, and are the form in which your body digests and absorbs carbs.

What are complex carbs?

These are both starchy and non-starchy food types and consist of 100’s of sugar units each, also known as polysaccharides. These can be found in the forms of maltose (sweet potato), sucrose (cookies) and lactose (cakes and biscuits). People who are lactose intolerant simply cannot digest this type of sugar effectively.  

What are Starchy Carbs?

  • Starchy carbs can be divided into resistant and digestible carbs. Resistant carbs, also known as amylose, slow down digestion due to their long unbranched chemical structure. These are good with respect to keeping you full since it takes longer for your body to digest them. These carbs are found in cereals including; corn, maize, rice, potatoes, beans, pulses and some vegetables.
  • Digestible carbs, also known as amylopectin, and are found in our small intestines. During digestion, enzymes break down its chemical structure, and in this process molecules branch off from the stem of that chemical structure, making them easier to digest than resistant carbs. Sources of digestible carbs include cereals, potatoes, beans, pulses and some vegetables. 

What are non-starchy Carbs?

  • Non-Starchy Carbs also known as fibre, and are obtained solely from foods of plant origin. We can safely say that fibre should be one of your best friends if you are trying to lose weight. Why? Let’s firstly discuss the thermogenic effect. Thermogenesis refers to the creation of heat within the body so you can burn more calories per day. When you consume thermogenic foods, your body burns more calories at rest due to the heat production. Fibre also adds bulk to your foods and keeps you fuller for longer. How? There are two types of fibre; soluble and insoluble.
  • Soluble Fibre can dissolve in water (blood) whereas insoluble fibre cannot. During digestion, soluble fibre will dissolve in water and take a form of gel-like mass which helps to slow digestion and absorption of carbohydrates like starch which helps you keep fuller and reduces spikes in blood sugar and reduces cholesterol levels. Whereas insoluble fibre does not dissolve in water but instead swells up from absorbing the water, therefore it moves through our digestive tract mostly undigested. Therefore, it helps to keep our gut clean and food moving and promotes regular bowel movement to reduce constipation and risk of bowel cancer. The recommended intake of fibre is 30g per day. However, if you are training to increase your muscle mass you should roughly consume 10-15g of fibre per 1000 daily calories (Norton and Baker,2019). 

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The complexity of carbs has been widely twisted over the years, but its important to remember that there are simple and complex carbs which are broken down into its constituent parts but in the end, they are all broken down into glucose which are small sugar molecules.

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Cho S, Dietrich M, Brown CJ, Clark CA, Block G. The effect of breakfast type on total daily energy intake and body mass index: results from the Third National Health and Nutrition Examination Survey (NHANES III). J Am Coll Nutr. 2003;22:296–302

Kevin, h. and Juen, G. (2019). Obesity Energetics: Body Weight Regulation and the Effects of Diet Composition. [online] pubmed. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568065/ [Accessed 17 Jul. 2019]. 

Norton, L. and Baker, P. (2019). Fat loss forever. 1st ed

Pi-Sunyer, X., Astrup, A., Fujioka, K., le Roux, C., Ortiz, R., Jensen, C. and Wilding, J. (2019). A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management | NEJM. [online] New England Journal of Medicine. Available at: https://www.nejm.org/doi/full/10.1056/NEJMoa1411892 [Accessed 17 Jul. 2019]. 

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