It seems like every culture expects guests to want to eat regardless of their circumstances, and if you refuse, you’re automatically rude and insulting.
If I offer you food and you refuse, I’m going to be quite happy. It means I get to save money and have more food to myself. I ain’t offering a second time if you say no the first time :maduro-coffee:
It's very rude to insist more than three times. Once for formality, twice for sincerity, three times to make sure. But after three offers you're pushing the issue and you need to accept their answer.