Irregular periods are not uncommon, and weight gain is linked with irregular menstruation in at least two ways. Weight gain and obesity might be considered a cause of an irregular period, or weight gain and an irregular period might be symptoms of a larger health issue.
What is Regular
Menstruation is the shedding of the uterine lining. Most women have menstrual cycles that last from 21 to 35 days, with menstruation usually lasting three to seven. Women's bodies might keep the same schedule of period length and days between periods. This is considered a regular cycle, though it is common for women to have changes in their cycle throughout their life.
What is Irregular
An irregular period, also known as irregular menstruation or an irregular menstrual cycle, can be characterized as an earlier than expected period, a later than expected period, a skipped period, bleeding in between regular periods, heavier menstrual flow than expected or lighter menstrual flow than expected. Many women will experience some form or irregular menstrual cycle at some point in their lives.
Weight Gain Leading to Irregular Periods
One known cause of an irregular period is a significant change in body weight. Obesity is associated with an increased risk for absence of a period, called amenorrhea; infrequent period, called oligomenorrhea; absence of ovulation, called anovulation; and a heavy or long period, called menorrhagia, as noted by Robert J. Norman, M.D., in the paper "Obesity and Reproductive Disorders: The Role of Practical Lifestyle Changes."
Polycystic Ovary Syndrome
Weight gain and irregular menstruation might appear as symptoms of polycystic ovary syndrome (PCOS). According to the National Women's Health Information Center, PCOS is the result of a hormone imbalance in the body. Increased androgens cause the ovaries to grow an ovum (egg), but not fully. The ovum is not released and might remain as an ovarian cyst. When ovulation does not occur, progesterone is not produced, leading to a missed or irregular period. It is also believed that insulin is related to PCOS; too much insulin can increase the production of androgens, which also cause problems with ovulation. If you believe your irregular periods and weight gain are because of PCOS, speak with your doctor.
Treatment of PCOS
Weight loss for overweight women can provide many health benefits. Healthy eating and exercise can often regulate a woman's menstrual cycle and might improve PCOS. Birth control pills also might be used to treat PCOS by regulating the menstrual cycle. Glucophage, a type 2 diabetes medication, has been used by doctors to treat PCOS, and it might lead to decreased body mass, though this is an off-label use of the drug.