We've heard enough about low-carb diets - they promote weight loss but can be dangerous. Why? How? What is really going on inside your body when you cut down on sugars and grains? If you are keen to dig a little deeper underneath your skin and fat tissue, read on. Here is the complexity of carbohydrate metabolism simplified for your easy-to-digest comprehension.

It is certainly true that the amount of sugars and grains you eat effects the size of your waist line. Fluctuations in hormones caused by the ingestion of carbohydrates make the burning or utilization of fats more difficult until all the glycogen or stored glucose is used up.

Eating a meal high in carbohydrates will cause the release of insulin, a hormone that allows cells to uptake glucose. However, insulin also acts on adipose tissue to inhibit the release of fatty acids and promote their synthesis. Since most people are trying to become leaner by burning fat through exercise, eating a meal before exercise may not be the best idea for losing weight. The best time of the day to exercise with the intention of losing weight is in the morning.

Carbs Before of After Exercise?

Then why is it that before almost any activity, most dieticians suggest a diet high in starch and other complex carbohydrates and low in fats and proteins? Fats and proteins take more time for breakdown and digestion than carbohydrates. This inhibits gastric emptying and may lead to cramping and acid reflux into the esophagus.

When you start exercising, blood circulation in the muscles takes over to supply oxygen and nutrients. The the sympathetic nervous system controls the mechanism of blood distribution and inhibits the function of gastrointestinal tract. Any fats or proteins in the stomach that haven't been properly digested would require blood supply diminishing efficiency of muscle work. Simple sugars are readily absorbed by the intestine and should be avoided because they cause rapid fluctuations in blood glucose, thereby affecting the circulating energy supply. Unlike simple sugars, starch found in potatoes, pasta and bread must be broken down into glucose before being absorbed into the blood. In this way, the energy can be absorbed more slowly and be available for longer than other simple sugars.

Since no food has been consumed since the last meal of the previous day, levels of insulin in the blood will be low. Furthermore, levels of glucagon will increase due to fasting and this hormone stimulates the release of fatty acids from adipose tissue while inhibiting the breakdown of glycogen from the liver. Epinephrine and Norepinephrine are also secreted in response to exercise and these hormones mimic the effects of insulin by increasing availability of fatty acids in the blood. Of course, fatty acids may only be utilized by working muscle under aerobic conditions. Therefore, in order to burn fats effectively, the ratio of insulin to glucagons must be low and the body must be performing exercise at a relatively low intensity for a prolonged period of time.

The release of glucose from stored liver glycogen and the synthesis of glucose by the liver acts to keep the blood glucose concentration stable during the fasting state. Taken together, these processes maintain blood glucose at a level adequate to support the activities of other tissues in the body, particularly the central nervous system. It is difficult to overstate the importance of the role of the liver in glucose storage and release to the healthy functioning of the whole body.

All cells of the body are capable of storing at least some glycogen, but the liver cells can store up to 5–8% of their weight as glycogen (although this drops to nearly zero after 18 h of fasting) and muscle cells can store up to 3% glycogen. Because of their relative mass compared to liver, most of the glycogen is stored in muscle, and though the glycogen in the liver is available for all cells via the blood, that in muscle is not easily converted to glucose for general use, even when hypoglycaemia is profound. The brain cells contain little glycogen and hence depend on a continuous supply of glucose for their high metabolic activity.

When there is no dietary glucose intake (between meals), circulating glucose concentration must be maintained. The pancreas secretes more glucagon and less insulin. The glucagon :
* stops liver glycogen synthesis (by deactivating the synthesis enzymes)
* increases liver glycogen breakdown (by activating the degradation enzymes)
* stimulates gluconeogenesis in the liver to further increase the circulating blood glucose concentration

To be continued...

Find Out More:

Where The Energy Comes From