When a person sets out to lose weight, especially if they are over 50lbs overweight, they usually lose a quick 5-15 pounds in the first couple of weeks. Many people are told “oh that’s just water weight” and they get discouraged. BUT THEY SHOULDN’T BE DISCOURAGED. That “water weight” loss is vital to being able to burn off stored fats. Most people do not realize how energy is stored in their body, and so do not understand the significant biological steps towards a healthy weight. The first step is using up your excess glycogen, which is where the “water weight” comes in.
When you eat, your body first breaks down the carbohydrates, fats, and proteins into the simplest form that it needs to be able to use them. The primary nutrients released into the bloodstream for our bodies to use are glucose, triglycerides, and amino acids. Glucose is the main energy fuel for most of your body’s energy needs. When there is more glucose in your blood than your body can use right away (which is usually the case after any meal), it is modified and stored for later use. One of these stored components is glycogen. The process that turns glucose into glycogen for storage takes in over 2 grams of water for every 1 gram of glycogen (so for each gram of glycogen stored you have over 3 grams of total weight added).
Glycogen is stored in liver and muscles tissues in your body, though some is also stored in the kidneys and intestine. When your body is active (even sleeping your burn energy) and runs out of glucose in the blood, the body begins to break down the stored glycogen so that your cells have the fuel they need. As your body converts glycogen back into glucose, it releases those extra grams of water, which are then filter through your kidneys and out they go.
How much glycogen a person stores is directly correlated to how much the person weighs. Your body normal stores enough glycogen so that your body has easy access to energy for multiple days in a starvation situation. The maximum amount appears to be 5g/kg of your body weight (1 pound = 2.2 kg). So if you are around 150lbs (68.2 kg), you could be storing around 341g of glycogen. At 3-4 grams total (remember over 2 grams of water is stored with each gram of glycogen) that is over 1348 grams of excess weight that as you burn off your glycogen, you lose in water as well. Once the stores of glycogen are depleted, then the body can begin to break down fats. First it takes the triglycerides that are in your bloodstream and liver, and breaks those down for energy (either as fatty acids for direct energy of broken down further into glucose). Then the stored fats are released, broken down first into glycerol and fatty acids, and then if needed into glucose.
As you go through your day and are burning off the glycogen. Within a couple of weeks, you will have used up the stored glycogen, and as you are eating less and exercising more, smaller amounts of glycogen will be stored. As you burn off each new storage of glycogen, your body will be able to access the stored fats that you are targeting. This is why you have an initial “water weight” drop in weight and then weight loss slows. Fat stores very little water with it, and thus after depleting your glycogen stores, you know that all of the weight you are losing is coming from the stored fats. So rejoice in losing the “water weight”, it means that now you can get into the nitty gritty and lose that stored fat.
Because a number of chemical and hormonal processes are required to adequately facilitate these transformations, you do need to keep a steady supply of fats, protein, and carbohydrate entering your body. Without the input of fresh, non-stored carbohydrates, fats, and protein, the body cannot be as efficient in breaking down glycogen or stored fats. The metabolism depends on a cycle of insulin to no insulin states of the blood, so ingesting the right amounts of the right food, at regular intervals will speed up weight loss (both use of glycogen AND stored fats). So use your food wisely, and talk to a doctor or nutritionist to get the best weight loss advice.
Resources used in this article:
Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 0-13-250882-6 .