Does intermittent fasting cause hair loss?

Why hair can shed after weight loss

Each hair grows for years, rests for a couple of months and then falls out as a new one grows. A shock to the body can push many hairs into the resting phase at once. Two to three months later they all fall out together. Doctors call this telogen effluvium. It's the most common cause of diffuse hair loss, and it's usually temporary: shedding tends to settle within about six months, although full regrowth can take a year or more ².

Sudden weight loss and a drop in protein are well-known triggers ¹. That's the real risk with fasting: not the clock, but a short eating window that quietly turns into eating far too little. The timing can be confusing, because the shedding starts weeks after the cause.

What about the mouse study?

This made headlines, so it's worth being clear about what it shows. Most of the work was in mice, whose hair grows very differently from ours. The human part was small and short, measured how fast hair grew, not whether people lost hair, and hasn't yet been repeated by other researchers ³. It's a reason for more research, not proof that fasting makes people lose their hair.

What helps

MYTH

Hair supplements will stop the shedding.

FACT

If you have a proven deficiency, correcting it makes sense. Without one, there's little evidence that supplements help, and some can make hair loss worse ¹. Ask a doctor before taking them.

Our guide to protein and muscle explains how to eat enough in a shorter window.

When to see a doctor

• You have patches of hair loss, a receding hairline or a widening parting, rather than general shedding.
• Your scalp is itchy, red, scaly or sore.
• Shedding lasts more than six months ².
• It comes with tiredness, feeling cold, missed periods or weight loss you didn't plan: a blood test can check things such as iron and thyroid ².

Sources

1. Guo EL, Katta R. Diet and hair loss: effects of nutrient deficiency and supplement use. Dermatol Pract Concept. 2017;7(1):1-10. doi.org/10.5826/dpc.0701a01
2. Malkud S. Telogen Effluvium: A Review. J Clin Diagn Res. 2015;9(9):WE01-3. doi.org/10.7860/JCDR/2015/15219.6492
3. Chen H, Liu C, Cui S, et al. Intermittent fasting triggers interorgan communication to suppress hair follicle regeneration. Cell. 2025;188(1):157-174.e22. doi.org/10.1016/j.cell.2024.11.004
4. Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376-384. doi.org/10.1136/bjsports-2017-097608
5. Leidy HJ, Clifton PM, Astrup A, et al. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015;101(6):1320S-1329S. doi.org/10.3945/ajcn.114.084038
6. Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. doi.org/10.3390/nu11040873