Where are extra calories stored in the body?Bart Loews:

This is more complicated than you think it is.

The first step is to stop thinking in terms of calories. Calories are a measurement of energy. It's like saying ”how do I save gallons?” rather than “how do I save gas?” in reference to your car.

Energy in your body comes from three sources: amino acids, glucose, and fatty acids.

Glucose is the simplest for your body to use. Fatty acids are the next, while amino acids take a little more work to break down.

All of them go through some metabolic processing to be broken down into acetyl-CoA, which is then broken down into ATP and used for energy.

Glucose is located in the bloodstream (blood sugar) and in your muscles and liver (glycogen stores). Your blood sugar levels are regulated by various glands. If they get low, your body is told to release energy from various stores to maintain its level.

Fatty acids are stored in adipose cells in the form of triglycerides. Fatty acids are also often found in your bloodstream as well, either as free fatty acids or cholesterol. Fats contain more than twice the amount of energy of glucose, but take a little more processing to get to and require oxygen to get there, while glucose can create energy without oxygen.

Amino acids are found in many places, primarily your muscles. If you need energy your body will break down muscles as well as fat to create that energy.

Glucose, amino acids, and fatty acids can all be converted to triglycerides. Triglycerides and amino acids can also be converted to glycogen for storage if your muscles and liver run low—this is the primary method that you lose fat through exercise, by your liver and muscles being replenished.

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