Does stevia break a fast?

Stevia sweeteners are made from extracts of the stevia leaf. Liquid drops can be close to pure stevia. One liquid stevia label lists only water, stevia extract and grapefruit seed extract, with 0 kcal and 0 g of carbohydrate per 4 drops. Packets are different. One 1 g stevia packet lists dextrose, a sugar, before the stevia. Other stevia packets, including Truvia, are mostly erythritol.

A label can say zero when the packet is not quite zero. US rules let a food be called calorie free when a serving has under 5 kcal. A 1 g packet with 1 g of dextrose can carry about 4 kcal, since sugar gives 4 kcal per gram. As a worked example, three packets in three coffees across a fasting morning add about 12 kcal and 3 g of sugar.

This site sorts answers by four goals, and stevia is a grey area for each of them. For weight loss the calories are close to zero. Some people find that sweet tastes make them hungrier, though the research on this is mixed. WHO also advises against using non-sugar sweeteners to control body weight, as a conditional recommendation. For blood sugar and autophagy, whether sweeteners raise insulin is unresolved and may vary between people, and the evidence is early.

Gut rest is grey because packets can bring dextrose or erythritol into your gut along with the stevia. Liquid drops with no bulking agent on the label give your gut the least to deal with. If you fast mainly for weight loss, a few drops in black coffee is a small trade-off. If you fast strictly for autophagy or blood sugar, plain black coffee or tea is the safer choice.