Take this medication 'on an empty stomach'. [=when your stomach is empty because you have not eaten for a time]
When I had the flu, just the thought of eating made me 'sick to my stomach'. [='nauseous']
She felt a flutter in 'the pit of her stomach' when he walked through the door.
(..) Oh, I've been hard at it. Sit down. Hard at what, exactly? Well, we're overwhelmed with work. Paperwork. Paperwork is the soul of Russia. Farming is only the stomach. Now, when am I going to come and shoot some snipe? Look at you, in Western clothes you told me you'd never wear again. (..)2012 Anna Karenina