How a Big Change in Your Weight May Affect Your Period

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Both weight gain and weight loss can cause you to skip your period and can help regulate your period.

Your menstrual cycle is a result of a complex interaction between your ovaries and your brain.  The coordinated changes in your hormone levels cause ovulation, and if you don't become pregnant in the days around your ovulation, more hormonal changes result in your period.

Anything that interferes with this interaction can stop your body from ovulating. If you miss an ovulation you will skip your normal period. 

What happens to your period when you have a significant fluctuation in your weight depends on what weight you are starting from. For example, if you are starting at a normal weight, gaining or losing weight may cause you to skip your period. While, if you are underweight or very overweight and not menstruating, gaining weight or losing weight will likely restart your regular period. 

Effects of Gaining Weight When Starting at a Normal Weight

If you have a normal range BMI and you gain weight it is possible that you may skip your period. There is no defined amount of weight gain that results in a missed period, but the more significant the gain and the shorter the time in which it happens, the more likely your period will be affected. Increasing your body's fat stores (aka adipose tissue) leads to a hormonal imbalance that can stop your ovulation.

The greater your BMI (typically in the obesity range of > 35) the more likely you are to miss your period. It is possible that you may stop bleeding altogether—a condition called secondary amenorrhea. It is also possible that you may have irregular noncyclic bleeding or abnormal uterine bleeding. Usually, when you are very overweight this irregular bleeding can be very heavy.

Effects of Gaining Weight When Starting Out Underweight

If you are underweight it is likely that you may not be getting your period. Typically calorie restriction excessive exercise or illness are behind your low BMI. These are stressors on your body that cause hormonal changes that interfere with ovulation. This also causes a very low estrogen level, which is especially bad for your bone health. When you gain weight you are reducing the stress on your body. This allows your body to ovulate again, and as a result, menstruate. It also restores your body's estrogen production and protects your bones.​​

Effects of Losing Weight When Starting at a Normal Weight

Just like weight gain, there is no defined about of weight loss that results in missed periods when starting from a normal weight. The more weight you lose and the faster you lose it, the more likely your period will be affected. Calorie restriction and strenuous exercise, both of which typically result in rapid weight loss cause a stress response in the body that changes hormone levels and interrupts ovulation and causes you to miss your period. As mentioned above, this results in a low estrogen level in your body, which is especially harmful to your bone health.

Effects of Losing Weight When Starting Out Overweight

If you are significantly overweight, especially if your BMI is > 35 it is likely that you are not getting your periods regularly. Your increased fat mass or adipose tissue produces extra estrogen that is partly responsible for problems with your ovulation and missed periods. The excess estrogen associated with obesity can increase your risk of breast and uterine cancer. Losing weight will restore your regular periods and correct your estrogen excess.

Having regular periods is a good indicator of relative hormonal balance in your body. Both the extremes of being very underweight or very overweight result in hormonal imbalances that stop your periods and over time can lead to serious health issues. You can correct the hormonal imbalances by either gaining or by losing weight to achieve a healthy BMI. This should restart your ovulation and your periods.

Maintaining your ideal body weight or roughly a BMI in the normal range (18.5-24.9) is one of the most important steps in achieving good health.

If you are starting on a plan to gain or lose weight it is a good idea to meet with your healthcare provider, a nutritionist, and maybe a personal trainer. Your goal should be to lose fat not lean body mass if you are overweight and to gain lean body mass, not just fat if you are underweight. Make lifestyle changes that will last the rest of your life.

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View Article Sources
  • American College of Obstetricians and Gynecologists. (2013). ACOG practice bulletin no.136: Obstet Gynecol.122:176-85