Hair loss. Those two words can send a shiver of sadness through your spine and freak you out. More so, when you have just ventured onto a new diet regime because you wanted to lose some weight, get healthy and fit and you see hair falling off your head like it is second nature.
Hair loss on a diet regime focussing on weight loss is an unintentional side effect, and in this article, we shall look into
a) why people on a diet regime focussing on weight loss tend to experience hair loss, and
b) how to prevent hair loss while trying to lose weight.
But first, a little science about hair.
The Science of Hair
Hair is basically dead protein. 95% of a single strand of hair is made up of keratin, and the rest of the 5% is made of keratin-associated proteins (KRTAPs). Keratin is a protein molecule that is synthesized by keratinocytes and is insoluble, thus rendering your hair waterproof. There is a total of 18 amino acids that play a part in the composition of a single hair strand – proline, threonine, leucine, cysteine, etc. of which cysteine is key as it forms bridges between keratin molecules and adds strength and rigidity to the strand.
Now, while hair is just a lot of dead cells, hair follicles on the other hand are living, breathing, metabolically active structures out of which hair grows. Hair follicles are interesting, in that, they are one of the few structures in the body that can degenerate and regenerate at any point in time. A small blood vessel at the root of the hair follicle provides the hair with all vital nutrients such as minerals, vitamins, and amino acids for it to be healthy. This means you need to consume enough calories and protein to feed your hair follicles to enable hair growth and keep hair loss at a minimum. Losing 50-100 strands per day is very normal as these are the strands that have completely detached from the hair follicles. In a state of optimal health, those hair follicles will allow for new hair to grow.
That said, the human body being the intelligent, living, dynamic bio-machine that it is, does not consider hair as an important tissue of the body. Your body can continue to function whether you have hair or not, however, it cannot function without a major organ like your brain, or heart. For this reason, hair follicles are the last to receive nutrients from the food, and supplements that we consume. 
Most people who experience hair loss while on a diet, are likely to be on a restrictive diet. Now, restrictive diets are diets that can be restricted by means of a significantly reduced number of calories, or eliminating entire food groups (not the same as an elimination diet, where you eliminate certain foods such as processed foods, sugar, gluten, etc. to identify what foods work well for your body) or both. Some of the very popular restrictive diets that have taken the world by storm are the Liquid diet, the Fruit diet, Low-Calorie diets (such as 1200 kcals/day, 500 kcals/day), etc. While most of these restrictive diets are fad in nature, their sole pitch is focused on losing weight at ease. There are also restrictive diets such as the Ketogenic Diet, the Gluten-Free diet, and Atkins Diet that limit certain foods or food groups, however, these diets are designed for people with existing medical conditions such as epilepsy, celiac disease, neurodegenerative diseases like Parkinson’s, etc. and not primarily for the purpose of weight loss. A restrictive diet, without medical supervision, when pursued for a prolonged period of time can be detrimental to health
Let me know if this works - When on a restrictive diet, you can miss out on a lot of favorite foods even though they are 100% healthy, but more importantly, your body misses out on a lot of nutrients it needs for optimal functioning. Specifically, diets like the liquid diet, and the fruit diet eliminate key food groups, resulting in fewer nutrients on your plate. Diets like the ketogenic diet, Atkins diet are healthy, in that they allow you to consume a plethora of nutrients from whole foods; however, it can be very challenging especially when you come with a lot of personal food preferences - for ex. you may be someone who eats meat, but you may choose to exclude organ meat on the grounds of personal choices, and that results in a lot of missing micronutrients on your plate. Many from the Indian diaspora who practise keto or the Atkins diet tend to exclude local, indigenous vegetables that are compliant instead leaning more towards cruciferous vegetables, and nightshades, making way for missing micronutrients. The human body needs approximately 30 micronutrients every day for optimal functioning, and restrictive diets allow for the possibility of low - no micronutrients on your plate. Hair follicles need a plethora of nutrients for sustenance, such as Zinc, Magnesium, Manganese, Iron, Folic acid, Vitamins A, C, D, E, K, Selenium, Biotin, Omega 3, and Polyphenols, and protein. Any diet that is devoid of or low on any or many of these nutrients, is going to result in poor hair quality, combined with hair loss., 
Now let us address the obvious question –
How do I avoid hair loss while trying to lose weight?
Food: The principal factor in the context of hair loss while on a new diet regime is food. The quality and diversity of your food are going to affect not just your hair health, but your overall health as well. Hair loss, or a change in the quality of your hair health is the first sign that you are under-nourished. Whatever diet you plan to go on for weight loss, make sure that it a) allows for adequate calories and does not eliminate any essential food groups in its entirety (for ex. no fats, or no carbs) and b) allows for a diversity of nutrients. Include berries, organ meats, good quality, organic grass-fed meat, bone broth, fatty fish, chicken, and eggs to get the whole spectrum of nutrients that your hair needs. Make sure you consume enough protein Do not forget to hydrate.
Supplements: Sometimes even when you allow for enough diversity of food on your plate, you may end up losing out on some of the key micronutrients that are necessary for healthy hair; or, it could be a case of personal preferences – for example, being a vegetarian; or, accessibility to quality produce. This is where supplements come into play. To understand what nutrients you are missing out on and what supplements you need to add, you have to get your blood work done, and then work with a functional practitioner to understand what supplements you need. Although it may be tempting to infer the results of your own blood work and get those supplements off Amazon based on advice from the internet, this is not recommended. Get an appointment with a qualified functional medicine practitioner to understand your body better and weed out those nutritional deficiencies at the roots. 
Stress: When you switch to a new diet regime, your body can experience stress. Although this is a temporary state- when left uncared for it can get worse and can result in hair loss by causing a large number of your hair follicles to go into a resting phase. To combat this stress, make sure you get enough sleep every night. You can incorporate yoga, and meditation to keep that cortisol in check. Go for long walks if you can, and try not to get overwhelmed in general. , 
Haircare routine: Ensure you have a good haircare routine in place. Give yourself some scalp massages every other day to improve blood circulation to your hair follicles. Use hair-care products that are free from harmful chemicals like sulfates, and parabens, and are gentle on your hair. A good litmus test for a hair-care product, aside from it being free of harmful chemicals is how your hair feels after using them. For example, if your hair feels too rough or dry after you wash it with a shampoo, it means your shampoo is stripping your hair of its natural oils, and that is not something you want as it can cause damage to your hair.
Ultimately, what you eat plays a huge role in your hair health. If you are someone who is already experiencing hair loss while having embarked on a diet, make sure you reach out to a functional practitioner and work towards transitioning to a more balanced and wholesome diet while incorporating healthy lifestyle changes in a holistic fashion.
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