Does sugar break a fast?

A level teaspoon of table sugar (4.2 g) has about 16 calories, and all of it is sugar. Your gut splits it into glucose and fructose. Blood sugar then rises, and insulin rises with it.

This site sorts every answer by four goals of its own. For blood sugar, autophagy and gut rest, sugar breaks the fast at any amount. It lifts blood glucose, and it is food your body has to digest. Weight loss is the one goal where a single teaspoon sits in the grey area. It is under the 50-calorie line, which is a common rule of thumb, not an official limit.

Teaspoons add up quickly. As a worked example, take two teaspoons in each of three teas or coffees during your fasting window. That is 6 teaspoons, about 98 calories and 25 g of sugar, well past the 50-calorie line. For someone eating 2,000 calories a day, 25 g is also half of WHO's daily limit for free sugars.

Sweeteners such as stevia and sucralose contain no sugar. Each has its own entry in this database. Whether they raise insulin is unresolved and may vary between people.

Sugar has other names on ingredient lists. Look for sucrose, glucose, dextrose, fructose, maltose, corn syrup, molasses, treacle, and agave or maple syrup. Brown sugar, cane sugar and honey count as sugar too.

If you have diabetes, sugar may be part of how you treat a low. Treat it the way your diabetes team has told you, whatever your fasting plan says. Break any fast if your blood glucose falls below 3.9 mmol/L (70 mg/dL).