Does gum break a fast?

What's in a piece of gum

Sugar-free gum is sweetened with sugar alcohols and zero-calorie sweeteners, which add a few calories per piece. Taken on their own, zero-calorie sweeteners didn't raise insulin in studies ^1,2, though taking sucralose every day for weeks lowered insulin sensitivity in two trials ^3,4. That's a reason to keep gum occasional rather than constant.

Gum	While fasting
Sugar-free gum, a piece now and then	Unlikely to matter
Sugar-free gum, piece after piece	Calories and sweeteners add up: keep it occasional
Gum with sugar, such as classic bubble gum	Breaks your fast

What about gum labelled 5 calories?

Read the ingredients rather than the calories. If the gum is sugar-free, its few calories come from sugar alcohols, and one piece is unlikely to matter. If sugar, glucose syrup or dextrose is on the list, it ends the fast, because sugar raises insulin ⁵.

MYTH

Anything sweet in your mouth makes your body release insulin.

FACT

In a British trial, simply tasting sucralose and spitting it out had no effect on insulin or gut hormones, and swallowing it didn't either ¹.

I chewed gum by accident. Is my fast ruined?

No. A piece of sugar-free gum is unlikely to matter, so carry on. If it had sugar, it's a small amount, and there's no need to give up on the day: carry on to your planned time, or eat when you're ready and start your next fast as usual. One slip doesn't undo the habit you're building.

If you're chewing because you're hungry

Hunger during a fast mostly comes in waves around your usual meal times. Your hunger hormone, ghrelin, almost doubles before a meal you're used to eating ⁶, and when people fast it still rises at those times and then falls again on its own, without food ⁷.

Sleep matters too: after two nights of short sleep, healthy young men had 28% more ghrelin and felt 24% hungrier ⁸.

Sources

1. Ford HE, Peters V, Martin NM, et al. Effects of oral ingestion of sucralose on gut hormone response and appetite in healthy normal-weight subjects. Eur J Clin Nutr. 2011;65(4):508-13. doi.org/10.1038/ejcn.2010.291
2. Tey SL, Salleh NB, Henry J, et al. Effects of aspartame-, monk fruit-, stevia- and sucrose-sweetened beverages on postprandial glucose, insulin and energy intake. Int J Obes (Lond). 2017;41(3):450-457. doi.org/10.1038/ijo.2016.225
3. Romo-Romo A, Aguilar-Salinas CA, Brito-Córdova GX, et al. Sucralose decreases insulin sensitivity in healthy subjects: a randomized controlled trial. Am J Clin Nutr. 2018;108(3):485-491. doi.org/10.1093/ajcn/nqy152
4. Lertrit A, Srimachai S, Saetung S, et al. Effects of sucralose on insulin and glucagon-like peptide-1 secretion in healthy subjects: a randomized, double-blind, placebo-controlled trial. Nutrition. 2018;55-56:125-130. doi.org/10.1016/j.nut.2018.04.001
5. Holt SH, Miller JC, Petocz P. An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr. 1997;66(5):1264-76. doi.org/10.1093/ajcn/66.5.1264
6. Cummings DE, Purnell JQ, Frayo RS, et al. A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Diabetes. 2001;50(8):1714-9. doi.org/10.2337/diabetes.50.8.1714
7. Natalucci G, Riedl S, Gleiss A, et al. Spontaneous 24-h ghrelin secretion pattern in fasting subjects: maintenance of a meal-related pattern. Eur J Endocrinol. 2005;152(6):845-50. doi.org/10.1530/eje.1.01919
8. Spiegel K, Tasali E, Penev P, et al. Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004;141(11):846-50. doi.org/10.7326/0003-4819-141-11-200412070-00008