Birth control really can cause weight gain, the American Journal of Obstetrics and Gynecology reports.

The worst offender is Depo-Provera, the contraceptive shot. Depo contains a synthetic hormone that keeps oestrogen levels low, preventing the release of eggs.

Women who used it were twice as likely as those who used non-hormonal contraceptives to become obese over three years, even after accounting for exercise and eating habits.

Here’s how to beat the creep:

Method:
Depo-Provera

Average weight gain over three years:
5kg

Average percentage increase in body fat:
3.41

Fight the flab:
If your diet and exercise habits stay the same after starting and you gain a lot, talk to your doc about other methods.

Method
The Pill

Average weight gain over three years:
1.5kg

Average percentage increase in body fat:
1.63

Fight the flab:
Women who strength-trained for at least two hours a week lost less kilojoule-burning muscle mass.