Individuals considering or using progesterone-only birth control often wonder about its potential impact on body weight. Understanding the relationship between these hormonal contraceptives and weight changes involves examining the different types available and the scientific evidence. This article explores various forms of progesterone birth control, what studies indicate about weight gain, and potential biological ways hormones might influence weight.
Types of Progesterone Birth Control
Progesterone-only birth control methods, also known as progestin-only methods, come in several forms. The mini-pill, or progestin-only pill (POP), is an oral contraceptive taken daily that works by thickening cervical mucus and sometimes preventing ovulation.
Hormonal intrauterine devices (IUDs), such as Mirena, Skyla, Kyleena, and Liletta, are T-shaped devices inserted into the uterus that release progestin locally. This thickens cervical mucus, thins the uterine lining, and can inhibit ovulation.
The contraceptive implant, like Nexplanon, is a small, flexible rod placed under the skin of the upper arm, continuously releasing progestin. It primarily prevents ovulation and thickens cervical mucus.
The contraceptive injection, Depo-Provera, delivers progestin via an intramuscular shot every three months. This injection works by inhibiting ovulation, thickening cervical mucus, and altering the uterine lining to prevent pregnancy.
Scientific Evidence on Weight Gain
The scientific evidence regarding weight gain with progesterone-only birth control is varied, with most large-scale studies indicating minimal or no significant average weight gain for many methods. Research often shows that for progestin-only pills, hormonal IUDs, and implants, most users do not experience notable weight changes. Any initial weight gain reported is frequently attributed to temporary fluid retention rather than an increase in body fat. A review of 49 studies found insufficient evidence to broadly link birth control pills with weight gain for most individuals.
However, the contraceptive injection, Depo-Provera, stands out as an exception. Studies consistently show a more direct association with weight gain for Depo-Provera users. Users of this method may gain an average of around 5 pounds in the first year, with some studies reporting up to 11.25 pounds over 36 months. This weight gain appears to be primarily due to an increase in fat mass, and it may be more pronounced in individuals who were not obese before starting the injection.
How Progesterone Might Influence Weight
Even if not universally observed, progestin could influence body weight through several biological mechanisms. One common effect is temporary fluid retention, which can lead to a feeling of bloating or slight weight increase, especially in the initial months of use. Progesterone can affect the body’s fluid balance by influencing the renin-angiotensin system, potentially causing the kidneys to retain more sodium and, consequently, water.
Progesterone may also play a role in appetite regulation and metabolism. Some research suggests that progesterone can stimulate appetite by affecting neurotransmitters that control hunger and satiety signals, potentially leading to increased cravings for carbohydrates. While progesterone supports metabolic activity and can slightly raise body temperature, which might increase calorie burn, it also promotes fat storage, particularly in the abdominal area. Individual responses to these hormonal influences vary considerably.
Other Influences on Body Weight
Understanding weight changes requires considering many factors beyond birth control use. Lifestyle choices, including dietary habits and levels of physical activity, play a significant role in weight management. Changes in diet, such as increased calorie intake, or reduced exercise can lead to weight gain regardless of contraceptive use.
Metabolic rates naturally shift with age, with adults often gaining a pound or two per year after age 40, partly due to a gradual slowdown in metabolism and a decrease in muscle mass.
Stress and sleep patterns also affect body weight. Chronic stress can elevate cortisol levels, which may promote fat storage, especially around the abdomen, and increase cravings for high-calorie foods. Inadequate sleep can disrupt hormones that regulate hunger and fullness, such as ghrelin and leptin, leading to increased appetite and a preference for less healthy food choices. These factors can independently contribute to weight fluctuations, making it challenging to isolate a single cause for any changes observed.
What to Do About Weight Concerns
Individuals concerned about weight changes while using progesterone birth control should discuss these concerns with their healthcare provider. Open communication allows for a thorough evaluation of potential causes and consideration of personalized strategies.
It is beneficial to review lifestyle habits, including diet and exercise, as adjustments in these areas can often help manage weight. Regular physical activity and a balanced diet remain foundational for maintaining a healthy weight.
If weight gain is significant or distressing, exploring alternative birth control methods with a healthcare professional is an option. Many different contraceptive choices are available, and one method’s effects may differ from another’s for a given individual. It is important never to discontinue birth control without medical advice, as this could lead to unintended pregnancy.