When choosing a method of family planning, many women fear weight gain associated with the birth control pill. In fact, there is no scientific evidence showing the pill causes significant weight gain. Injectable hormonal birth control, however, does contribute to weight gain, according to a 2009 study at the University of Texas Medical Branch. If you find yourself gaining weight several years after discontinuing the birth control pill, it is unlikely the pill itself is to blame.
Function
Birth control pills contain a hormone -- or hormones -- functioning to prevent ovulation and thereby prevent pregnancy. Hormonal birth control pills are between 98 and 99 percent effective at preventing pregnancy, according to MayoClinic.com. Taking the birth control pill irregularly or not as prescribed reduces its effectiveness. With some formulations, it is necessary to take the pill around the same time each day.
Possible Causes of Weight Gain: Age
If you experience weight gain several years after discontinuing use of the birth control pill, your age may be a contributory factor. In general, your body's daily calorie requirements will decrease slightly as you get older; therefore, if you continue to eat the same number of calories over a period of years, it is likely your weight will increase unless you also increase the number of calories burned daily through exercise. According to the MayoClinic.com calorie calculator tool, a 21-year-old woman who is 5 feet 6 inches and weighs 150 pounds needs 2,200 calories per day if she maintains an active lifestyle. At age 30, the same woman at the same weight and activity level requires only 2,150 calories per day.
Possible Causes of Weight Gain: Childbearing
If the reason you stopped taking the birth control pill several years ago was to bear children and raise a family, this in itself may contribute to subsequent weight gain. Pregnancy involves significant -- albeit temporary -- weight gain, and many women struggle to lose the "baby weight" after giving birth. According to a January 2010 report on Medical News Today, young women often find that weight gain happens concurrently with the early years of their child's life, when there may be less time to exercise.
Insight
Despite popular belief that the birth control pill can cause weight gain, this link has yet to be proved scientifically as of 2010. Perceived weight gain while taking the birth control pill may in fact be due to fluid retention in the thighs, hips and breasts while you are taking the pill. You may be able to reduce weight gain or fluid retention by taking a birth control pill containing only a low dose of the estrogen hormone.
Warning
Any unexplained or unexpected weight gain should be discussed with your doctor, as this could be a symptom of an underlying medical condition or problem. The birth control pill can cause health problems in susceptible women -- the risk of blood clots, for example, may increase with birth control pill use. Additionally, the birth control pill offers no protection against sexually transmitted diseases or infection.
