When not to fast

Fasting isn’t right for everyone, and a few situations are clear enough that Vida would rather say so plainly than hedge.

When shouldn’t you fast?

• If you’re pregnant or breastfeeding. Your body needs steady fuel, and this app isn’t built for that season.
• If you have a current eating disorder.
• If you’re underweight, or your period has stopped and you don’t know why.
• If a doctor has told you not to.

When should you talk to a doctor first?

• Diabetes, especially on insulin or medication that can lower blood sugar. The timing genuinely matters here and needs supervising.
• Any medication that has to be taken with food.
• A history of disordered eating, even if it was years ago.
• Heart, kidney or liver conditions.
• If you’re in treatment for anything, or recovering from surgery.

None of those are an automatic no. They’re conversations, and the person who prescribes your medication is the right person to have them with.

What if you have a history with food?

This deserves more than a line. In a large study of young people, intermittent fasting was associated with more eating-disorder behaviors and related distress, particularly among women.1

It’s an association rather than proof that one causes the other. It’s a strong enough signal to take seriously if restriction has been difficult for you before.

Fasting gives structure to eating, and structure is useful right up until it becomes a way to keep score.

Those two can look identical from the outside and feel completely different from the inside.

What are the signs it’s turning into something else?

• You feel anxious or guilty when a fast gets interrupted.
• You’re extending fasts because stopping feels like losing.
• You’re avoiding meals with other people to protect the window.
• Eating on time feels like failing.
• You think about food far more than you used to.
• The number on the clock matters more than how you feel.

If several of those are true, the useful move is to stop fasting for a while and talk to someone. Not to find a gentler protocol.

And the physical side?

Consistently taking in less than you spend has consequences for your cycle, bones, mood and immune system, and a cycle that changes or disappears is the clearest early signal you’ll get. Clinically that’s something to investigate, never a sign of progress.23

For most people most of the time, fasting is well tolerated. Across fifteen randomized trials, dropout, fatigue and headache were about the same as in control groups. This page exists for the times when that isn’t you.4