Quick answers
Does lemon water break a fast?
Water with lemon slices is fine. Here's why, and how water makes a fast easier
Why plain water fits a fast
What ends a fast, if you want your body to run on stored fat, is anything that pushes insulin back up, the signal that tells your cells to store fuel instead of releasing it. Water has no calories and doesn't raise insulin. A slice of lemon adds flavour, not a meal.
Water makes fasting easier
Many of the most common complaints on a fast, such as a dull headache or feeling flat, have more to do with water than with hunger. When young women lost just over 1% of their body weight in water, they reported more headaches, more fatigue and worse mood 2. About 1 in 10 people recognise a water-deprivation headache, and for most it passed within 30 minutes of drinking around half a litre of water 3.
Water may help with hunger too. In a 12-week trial, adults who drank 500 ml of water before each meal lost about 2 kg more than those on the same diet without it, partly because they ate less at those meals 4.
Fine while fasting
- Water, still or sparkling, with lemon or cucumber slices.
- Black coffee, hot or iced, and plain, green or herbal tea without sugar or honey.
- A pinch of salt or sugar-free electrolytes on longer fasts 5.
Sources
- 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
- Armstrong LE, Ganio MS, Casa DJ, et al. Mild dehydration affects mood in healthy young women. J Nutr. 2012;142(2):382-8. doi.org/10.3945/jn.111.142000
- Blau JN, Kell CA, Sperling JM. Water-deprivation headache: a new headache with two variants. Headache. 2004;44(1):79-83. doi.org/10.1111/j.1526-4610.2004.04014.x
- Dennis EA, Dengo AL, Comber DL, et al. Water consumption increases weight loss during a hypocaloric diet intervention in middle-aged and older adults. Obesity (Silver Spring). 2010;18(2):300-7. doi.org/10.1038/oby.2009.235
- Sigler MH. The mechanism of the natriuresis of fasting. J Clin Invest. 1975;55(2):377-87. doi.org/10.1172/JCI107941
Keep reading
- Does tea break a fast?Plain, green and herbal tea are fine. Sugar, honey and milk are what break a fast
Water, salt and electrolytesWhy fasting changes how your body handles water and sodium, and when it's worth doing something about it
What breaks a fast (and what doesn't)Coffee, milk, sweeteners and supplements, judged by what they do to your body
A note on health
Fasting Tracker is designed for general wellness and is not a medical device. Fasting is not right for everyone. If you are pregnant, diabetic, have a history of eating disorders or take medication, talk to your doctor first, and before any extended fast.