Many young women do not want to start taking the contraceptive pill because they are worried that they will put on weight, or come off it because they think that they have gained weight because of it. However, a thesis from the University of Gothenburg, Sweden, has demonstrated that the combined contraceptive pill does not cause weight increase.
In her thesis, Ingela Lindh reports on a long-term study of 1,749 women born in 1962, 1972 and 1982 who answered questions about matters such as contraception, pregnancies, height/weight and smoking habits every five years from the age of 19 to 44.
"The women who were on the pill and were monitored from their teenage years until the age of 34 didn't put on any more weight than their peers who had never taken the pill at all," says Lindh, a registered midwife and researcher at the Sahlgrenska Academy.
The study also showed that the combined pill is the most widely used contraceptive up to the age of 29, after which condoms are most common. From the age of 32 onwards the coil proved most popular.
"There were lots of reasons why women came off the pill, including a fear of side-effects, weight gain and mood swings, and these gradually increased over time and were more common in the youngest group," says Lindh.
Despite women's concerns about weight gain, the researchers did not find any link between being on the pill and putting on weight. The only factors that affected weight were ageing and smoking. The number of smokers among the 19-year-olds born in 1962 was on average of 42%, compared with 29% among those born in 1982. At the same time, average weight rose by 3.2 kilos between these two groups. In the youngest group, women from low socioeconomic status areas were heavier than their peers. By following the same women from the age of 19 to 44, the researchers were able to calculate that they gained an average of 10.6 kilos, which works out at around 0.45 kg a year.
Lindh would like this new knowledge to increase the use of the combined pill and thus reduce the risk of unwanted pregnancies.
"It's important to let women know that the pill doesn't affect their weight, as there's a real fear that they will put on weight, especially among young women, and this can be one of the reasons why they don't want to go on the pill. When giving advice about different types of contraception, we should also tell young women about the importance of lifestyle factors such as diet and exercise so that we can break this trend of heavier teenagers."
The combined pill contains synthetic forms of the female sex hormones oestrogen and progesterone. It is estimated that 80-90 million women use the pill worldwide, and that around 400,000 of them are Swedish. It is the most commonly used form of contraception among young women in Sweden.
The thesis was successfully defended on May 27, 2011.