Under non-dieting conditions the primary source of fuel that the body uses for energy is its blood sugar. When that blood sugar supply gets low the body has reserves of sugar which are stored as a complex molecule called glycogen. Glycogen is stored in the body bound to a great deal of water.
When we change the amount of glycogen in the body we also change the amount of water. Glycogen and water are heavy. Changes will affect our weight a great deal and in a very short timespan.
After dieting the body will again need glycogen and it will be restored with the reintroduction of food. A few simple facts about glycogen...
Glycogen is made of sugar and is, therefore, a carbohydrate.
A pound of glycogen is worth about 1800 calories. 1800 calories deficit in the daily intake can use up a pound of glycogen from the storage.
Glycogen is stored with about 4 parts of water for each part of glycogen. This means that a pound of glycogen may hold and additional 4 pounds of water. 1800 calories of calorie deficit in the food eaten can cause a 5 pounds weight poss. Compare that with the real need for fat loss. The same 1800 calorie deficit will only use up 1/2 pound of fat.
Glycogen is stored in the liver, muscles and fat cells of the body. The amount we can store can vary depending upon what we eat and how much we use our muscles. Recent research suggests that some people may store as much as a kilogram of glycogen that can be mobilized in the first few days of using a vlcd. This could mean that such a person could lose almost a stone in weight during the first few days of dieting and not yet have burned any fat.
Glycogen is use up and replaced as a matter of course all the time. Think of the glycogen stores the way you think of a kitchen jug that contains sugar. When the levels get low it is easy to fill it up. Daily activities of living and sleeping use glycogen up. Eating fills glycogen stores back up, every day.
The average person uses up about 2000 calories energy each day so that difference between energy used up and energy eaten means that the body's reserve stores of sugar and fat are drawn on to meet the body's needs.
In this way body weight is lost. You are not actually living on reduced calories, you are only changing the place the calories come from.
The sugar content of the diet is kept deliberately low so that the body's own sugar stores get used up quickly. Fat then becomes the major source of energy.
When fat is burned rapidly, the body produces substances from the fat called 'ketone's' and the person is said to be in 'ketosis'.
Source: Lipotrim.
Hope this helps.
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