Does sucralose break a fast?

Sucralose is a non-sugar sweetener sold in packets, tablets and liquid drops. A typical 1 g sucralose packet lists dextrose with maltodextrin first and sucralose last, with 1 g of carbohydrate and 0 kcal on the label. US rules allow a zero-calorie label for any serving under 5 kcal, so each packet carries up to about 4 kcal. Liquid sucralose is mostly water, and one label lists 0 g of carbohydrate per serving.

Two human studies have tested sucralose and blood sugar directly. In a 2013 study of people with obesity who did not normally use sweeteners, sucralose changed their blood-sugar and insulin response to a glucose drink. In a 2022 trial, sucralose and saccharin worsened blood-sugar responses in some people, linked to changes in their gut bacteria. The evidence is early, and the effect may vary between people.

This site sorts answers by four goals, and sucralose is grey for each one. Blood sugar is grey because of the findings above, and gut rest is grey because of the gut-bacteria link. Autophagy is grey, as it is for every non-caloric sweet taste. Weight loss is grey too. The calories are tiny, but WHO advises against non-sugar sweeteners for weight control, as a conditional recommendation.

As a worked example, one packet in each of three coffees adds up to about 12 kcal and 3 g of dextrose across a morning. For a weight-loss fast that is small, well under the common 50-calorie rule of thumb, which is not an official limit. If blood sugar is your reason for fasting, liquid sucralose avoids the dextrose but leaves the open questions above.