In 2007, Oprah and Dr. Oz explained what a momentum is. It is an organ that is split into greater and lesser omentum. The greater omentum is right in front of your stomach, while the lesser omentum covers the liver.
The omentum stores your fat. When you loose weight, your omentum will also decrease in size. It can also stores hormones (cortisol). So if you have a lot of stress at work every day you will have a hard time to reduce the size of your omentum.
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Omentum explained on Wikipedia
What’s a healthy omentum size?
Measure around your body, crossing the belly button. Your values should not exceed 32 inches for a woman and 35 inches for a man.