Pot belly is caused by that the intestines themselves are going forward.
That means that pot belly is caused by the looseness of the muscles covering the intestines.
Iliopsoas is a muscle which connects the spine and the legs and is the key to lose weight. Weakness of iliopsoas gives you a bent back, causing pot belly, but if you strengthen iliopsoas, you can flatten your stomach and have good posture.
Exercise to strengthen iliopsoas
Starting posture (Fig. 1)
Another exercise (Fig. 3)
It is good to exercise 2 hours after meals because the energy of protein that is the material of the muscles can be used 2 hours after meals. If you exercise when you are hungry, the muscles can be broken down and used as energy.