The Reason Losing Weight Might Cause Hair Loss

If you've recently lost a significant amount of weight in a short period of time, you may have noticed an unwelcome side effect: hair loss. There are a few potential reasons that your hair is falling out at a rapid rate, and while this type of hair loss can be reversed, it's an important warning sign that your body is under significant stress.

The primary reason that your hair may be falling out in clumps or just shedding at a faster rate than normal is simply that you've created a too-big caloric deficit — basically eating less than your body needs to function. This leads to faster weight loss, but comes with health risks. Not getting enough calories or nutrients can lead to hair loss, and your hair will continue to fall out until you correct the deficit and find a healthier caloric balance (via Business Standard). Low iron in your diet may also be to blame (via Verywell Fit). 

You can still continue to lose weight, but you may need to slow down the process. Generally speaking, the Mayo Clinic recommends only aiming to lose between one and two pounds per week, which means a caloric deficit of around 500 calories per day. And the caloric deficit you create should still leave room for eating primarily healthy whole foods, including fruit, vegetables, lean protein, and healthy fats — not just calorie counting. Nutrient density matters, especially when it comes to healthy bodily functions (like hair growth).

What else can cause hair loss during weight loss?

Mental and emotional stress can also lead to hair loss, so if you're finding sticking to a diet and exercise regimen particularly taxing, or you're going through emotional upheaval or a tough time at work, the stress may be the root cause of your hair falling out. This is medically referred to as telogen effluvium, and the good news is that as your stress levels lower, your hair will eventually grow back (via the Mayo Clinic). If you think your hair loss is more stress-related, look for ways to decrease stress in your life — possibly even dialing back aggressive diet and weight loss goals until you're feeling better.

There may also be a hormonal issue at play: If you've noticed hair loss in the past as well, consider getting your thyroid checked, since many thyroid conditions (especially an overactive thyroid) can contribute to hair loss. 

The good news is that as your weight levels out and you stop actively trying to lose weight once you hit your goal, your hair will likely grow back. "When people stop losing weight, the hair loss usually resolves itself," dietitian Beth Warren told Women's Health.