Cereals can be refined like white pasta and rice or unrefined which means that the fibre has not been removed and therefore they are high in complex carbohydrates.
Complex carbohydrates help maintain our energy levels stable as energy from these foods is released slowly. Refined carbohydrates as those find in sugar, white bread, confectionery, etc are very rapidly digested to glucose that then enters our bloodstream leading to quick rises of energy followed by energy slumps, which leave us wanting more quick-release energy foods, i.e. sugar cravings.
Diets high in refined sugars require large amounts of insulin, the hormone that helps transport glucose into our body cells for the production of energy, to be released on a continuous basis. This process could eventually make our cells less sensitive to insulin preventing glucose transport into the cells and leading to high blood sugar levels and, potentially, type 2 diabetes.
High levels of blood glucose and insulin have been associated with high levels of the enzyme that triggers cholesterol production. Also, when both glucose and insulin levels are high, glucose is converted into fatty acids and stored in adipose tissue promoting weight gain.
Lastly, refined cereals have been stripped of many nutrients including B vitamins that are needed to produce energy from foods.
Widely available cereals contain complex carbohydrates include wholewheat pasta, flour, cereal and bread and to a lesser extent brown and granary bread, buckwheat flour and noodles, rye bread, spelt grain and wholemeal spelt pasta and flour, oats, porridge, oat cakes barley, quinoa and amaranth (although they are seeds rather than cereal) and brown rice.
Other foods containing complex carbohydrates are fruits and vegetables, pulses, beans, nuts and seeds.