Nausea more often?

It used to happen to me a lot when I restricted food. Usually, when I'd diet, I'd cut fat pretty low. Then I'd have fast food or something with high fat and my stomach would be upset. I assumed it was because it was "bad" food.
I came to learn later that it is just because your stomach becomes accustomed to one thing and when you eat different, it can get upset.
Eat low fat for awhile, add a lot of fat at once and you'll likely experience upset stomach. It doesn't matter the source, it can happen with "good" fat.
The same happens when you eat a bland diet and add spicy. Even increasing your intake of veggies can cause stomach discomfort.
It also happened to me when I stopped eating meat for awhile and reintroduced it.