The fat didn't really leave his body. Fat was converted to glucose in the gluconeogenesis pathway to give him energy during the period of starvation.
Fat is stored in the body in the adipose tissue. Fat plays so many roles in the body such as;
In times of starvation, fact could also be broken down to release energy. This occurs when fat is broken down to glycerol and fatty acids. When this occurs, glycerol goes to the liver where it is converted to glucose in the gluconeogenesis pathway. This helps to produce energy in times of starvation thereby depleting the body's fat reserve.
As this process occurs, the fat reserve in my friend's body kept going down resulting in his loss of about 15 Ibs of weight.
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