Why Weight Loss May Cause Hair Loss

Hair loss can be an unexpected side effect of significant weight loss. Whether the weight loss is due to medical treatment, surgery, or a restrictive diet, sudden changes can stress the body, sometimes causing hair to shed. This temporary hair loss, known as telogen effluvium, is often triggered by nutrient deficiencies, hormonal shifts, or the physical stress of rapid weight loss.

In this blog, we explore why hair loss happens with weight loss and share simple ways to help keep your hair healthy while achieving your weight goals.

Telogen Effluvium

Your hair grows in cycles made up of four phases:¹

• Anagen: The growth phase, lasting several years, when hair follicles actively produce hair.
• Catagen: The transition phase, lasting about 10-14 days, where hair follicles detach from the skin.
• Telogen: The resting phase, lasting a few months, where hair follicles are inactive.
• Exogen: The shedding phase, when hair falls out.

In telogen effluvium, more hair follicles than usual enter the resting phase, resulting in noticeable shedding. Usually, only about 10-15% of hair is in this phase, but with telogen effluvium, this number can increase due to stressors like rapid weight loss, illness, or a sudden dietary shift.²

Why Weight Loss May Cause Hair Loss

Nutrient Deficiencies

• Protein: Hair is largely made up of a protein called keratin. If protein intake is too low, the body uses available protein for essential functions, slowing hair growth and causing shedding.^3,4
• Iron deficiency: Iron helps transport oxygen in the blood to hair follicles. Since blood supply is prioritized over hair growth, the body sheds hair before red blood cell levels drop significantly. Low iron levels, especially common in restrictive diets, can lead to anemia and impair hair growth. Premenopausal women are more at risk due to menstruation.^1,2,5
• Vitamin D: Vitamin D deficiency is linked to hair loss, especially telogen effluvium. Vitamin D supports the hair growth cycle by activating receptors in hair follicles, which are essential for starting new hair growth.^1,3,6
• B vitamins: Studies suggest that low folic acid levels are linked to hair loss after metabolic or bariatric surgery, as patients with hair loss often show lower folic acid levels. The data on vitamin B₁₂ is less consistent; while some cases of hair loss showed lower B₁₂ levels, findings were too varied to confirm a strong link.⁵
• Zinc: Studies indicate that people with hair loss often have low zinc levels, and supplementation may help if deficiency is confirmed. Zinc supports cell division and hair follicle health, with risk factors for deficiency, including malabsorption issues, certain medications, and vegetarian diets. Since excess zinc can be harmful, testing before supplementation is advised.^1,3,5

Rapid Calorie Restriction

Rapid calorie restriction can trigger telogen effluvium, causing hair follicles to shift prematurely to the resting phase and leading to widespread shedding. A study in JAMA found that individuals on strict weight loss plans experienced significant hair loss within two to five months, with telogen counts rising from 25% to 50%. This occurs because severe calorie cuts limit energy to hair follicles, disrupting growth.⁷

Hormonal Changes

Quick weight loss can disrupt hormones that help regulate hair growth.¹ A study found that dieting in normal-weight females lowered levels of hormones like leptin and estrogen, which help control hair growth. These hormone shifts can lead to increased hair shedding. While most hormonal levels return to normal within a few months of increased energy intake, it's crucial to approach weight loss sustainably to mitigate the risk of hair loss and other health issues.⁸

Stress and Lifestyle Factors

Weight loss can also create physical and emotional stress, especially with illness or major lifestyle changes. This stress can cause more hair follicles to enter the shedding phase, amplifying hair loss.¹

How to Support Healthy Hair During Periods of Weight Loss

Prioritize Balanced Nutrition

• Protein: Aim to meet your daily protein needs to ensure your body has enough for essential functions and hair health. Try including lean meats, fish, eggs, tofu, and legumes. If you're following a restrictive diet, consider adding an Unjury^® protein supplement, and consult your dietitian for personalized guidance.
• Iron: Include iron-rich foods like spinach, lean meats, and beans, and use an iron supplement if a deficiency is confirmed. For better absorption, pair iron sources with vitamin C-rich foods (e.g., bell peppers, oranges).
• Vitamin D: Because it’s hard to get enough vitamin D from food alone, try to spend time outdoors in sunlight. If you’re low on vitamin D, discuss supplementation with your healthcare provider.
• B vitamins: Ensure you’re getting adequate B vitamins, especially folic acid and B₁₂. Leafy greens, eggs, and fortified cereals are good sources. After bariatric surgery, a multivitamin is essential, so talk with your provider about supplementation.
• Zinc: Add zinc-rich foods like nuts, seeds, and shellfish to your diet. Since excess zinc can cause other issues, consult a provider and test your levels before supplementing.

Check out Hair Skin and Nails.

Calorie Management

• Avoid extreme calorie cuts, as rapid restriction can lead to telogen effluvium (hair shedding). Aim for a gradual calorie reduction to support sustainable weight loss without compromising nutrient supply or hair health. Speak with a dietitian to determine a safe calorie goal.

Manage Hormonal Changes

• Rapid weight loss may disrupt hormones critical for hair health, such as leptin and estrogen. Opt for a balanced approach to weight loss to help maintain stable hormone levels.

Reduce Stress

• Hair health is closely linked to stress. Consider stress-reducing practices such as mindfulness, yoga, or regular exercise to support mental well-being during your weight loss journey.

Take Care of Your Scalp and Hair

• Scalp care supports overall hair health. Softly massaging the scalp can stimulate blood flow to hair follicles. Avoid tension-inducing hairstyles, minimize heat styling, and use gentle shampoos and conditioners.

Regularly Monitor Your Nutritional Status

• If you’re undergoing rapid weight loss or following a restricted diet, consider regular blood tests to monitor nutrient levels like iron, vitamin D, and B vitamins. Partnering with a healthcare provider can help you adjust supplementation as needed to maintain balanced nutrition.

A Note on Biotin

Biotin, found in protein-rich foods, is essential for hair and skin health. Supplementation may be recommended for deficiencies; however, true deficiency is rare. While biotin primarily supports hair strength, not growth, it’s regularly included in hair, skin, and nail supplements due to its benefits for brittle nails. Unless there is a known deficiency, biotin supplementation is unnecessary and can interfere with lab tests, including thyroid and heart markers. Biotin supplements are generally unnecessary if dietary intake is adequate.^1,3

Conclusion

Hair loss during weight loss can be frustrating, but understanding the causes and taking steps to support your nutrition and overall well-being can help. By focusing on balanced nutrition, gradual calorie reduction, and caring for both your scalp and mental health, you can reduce hair shedding and encourage healthy growth.

Remember, weight loss is about supporting your entire health, including your hair. Consult with a healthcare provider for guidance, and take small steps to keep yourself looking and feeling your best throughout your journey.

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References

1. Natarelli N et al. J Clin Med. 2023;12(3):893.
2. Hughes EC et al. Telogen Effluvium. [Updated 2024 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430848/.
3. Guo EL et al. Dermatol Pract Concept. 2017;7(1):1-10.
4. Lin RL et al. Annals of Medicine. 2016;48(6):393-402.
5. Zhang W et al. Obes Surg. 2021;31(6):2649-2659.
6. Zubair Z et al. Cureus. 2021;13(12):e20431.
7. Goette DK et al. JAMA. 1976;235(24):2622-2623.
8. Hulmi JJ et al. Front Physiol. 2017;7:689.