What can break a fast?

The question of what can break a fast is complex and highly contextual. It depends on factors like when you last ate, what you ate, your activity levels, and where you are in your circadian cycle.

Here are some general guidelines:

1. Drinking water, tea, or black coffee will not break your fast.
2. Ingesting small amounts of food, like a single peanut, might not break your fast if you're in a very low glucose state. However, if you've recently eaten a large meal or consumed carbohydrates, even a small amount of food could break your fast.
3. Consuming anything with sugar, especially simple sugars, can potentially break your fast. This is particularly true if you've recently eaten a full meal.
4. Consuming purely fats, like medium chain triglycerides (MCTs), probably won't break your fast if you've been strictly fasting for five hours or more.

Remember, these are general guidelines and individual responses can vary. If you want a more precise understanding of what breaks your fast, you could consider using a continuous glucose monitor to track your blood glucose levels.