Before a speech, interview, first date, or important event, your stomach may suddenly feel as though it contains a small flock of birds.
Nothing is actually fluttering inside it.
Your digestive system is reacting to stress signals from the nervous system.
Your brain and gut are closely connected
The digestive tract contains an enormous network of nerves.
It also communicates constantly with the brain.
That is why emotions can produce physical sensations in the stomach and intestines.
Stress activates the sympathetic nervous system
When you feel anxious or excited, the sympathetic nervous system becomes more active.
This is part of the fight-or-flight response.
Heart rate may rise.
Breathing can change.
Muscles tense.
The body begins prioritizing immediate action.
Digestion becomes less important for the moment
During a stress response, the body can change digestive activity.
Hormones such as adrenaline also influence nerves and muscles in the gastrointestinal system.
That can create fluttering, tightness, nausea, cramping, or even the sudden need to use the bathroom.
Why does excitement cause the same feeling?
The nervous system responds to arousal, not just fear.
Excitement and nervousness can produce many of the same physiological changes.
That is why butterflies can appear before something you desperately want to do as well as something you dread.
Is this related to being “hangry”?
Only indirectly.
Hunger can affect mood through a different mixture of physical discomfort and regulatory signals.
Nervous butterflies are more directly tied to emotional arousal and the brain-gut connection.
Why do people feel stress in different places?
Bodies vary.
One person gets butterflies.
Another gets sweaty palms.
Another blushes.
Another feels their heart pounding.
Many stress systems activate together, but individuals notice different pieces more strongly.
So nothing is flying around in your stomach.
Your gut is responding to the same stress signals affecting the rest of your body.
And that’s the short explanation.
Related explanations: Why do we blush?, Why does your stomach growl?, and Why do we get hungry?