Carbohydrates are the main energy source in all living organisms.
1g carbohydrate = 4 calories.
They are a non-essential macronutrient, however the brain and nervous system use glucose as their primary fuel source and require a continuous supply. Glucose can be created from other compounds like protein if necessary.
Carbs almost always have a place in the diet and do not need to be removed in order to see changes with body fat.
Carbohydrates can be categorised into groups, these are:
Complex starchy carbs
Complex fibrous carbs
Starchy carbs can be separated one step further into refined/ processed carbs and less refined/ more wholegrain carbs.
Note that none of these categories are 'good carbs' and 'bad carbs' as this is a grossly reductionist and potentially harmful way to view nutrition.
Simple sugars can be separated one step further into:
Intrinsic sugars: sugars found within the cellular structure of foods, e.g. sugars in fruits and vegetables.
Extrinsic sugars: sugars not bound by cellular structure, e.g. lactose in dairy products, honey, fruit juices, table sugar and confectionery.
All of these categories have utility as part of a balanced diet and all carbohydrates are broken down into simple sugars during digestion.
Simple sugars will break down more quickly, whilst complex carbohydrates will break down more slowly.
However, the macronutrient composition and thus caloric load of the meal they are consumed with will also influence the rate of digestion (Gropper, 2017).
Most carbohydrates contain a mix of sugars and starches with some fibre. By observing the table above we can see that white bread is a more starchy carbohydrate with 42g of its 46g carb content coming from starches. Raisins on the other hand have zero starch and are composed of mostly sugars.
Check out the lists below for a handy guide to categorising carbohydrates.