The purpose of this study is to learn if women gain weight using progestin-only methods of contraception and if so, how much. The investigators will look at users of two progestin-only methods: the levonorgestrel-containing intrauterine contraceptive (LNG-IUC) and the etonorgestrel (ENG) subdermal implant, and compare these users' weight change to that of users of a non-hormonal method, the copper intrauterine device.

The primary hypothesis is that ENG implant and LNG-IUC users' weight and body composition will increase more than the copper-IUD users. The investigators will collect body composition data using dual-energy x-ray absorptiometry (DEXA), and collect information about diet and activity using validated questionnaires.

The study has finished enrolling new participants.

Inclusion Criteria:

• Participants between the ages of 18 and 45 years
• Participants starting the copper IUD or implant through their provider
• First study visit must occur within 14 days of method insertion

Exclusion Criteria:

• DMPA in the past 16 weeks
• POPs, LNG-IUC, or the implant in the past 4 weeks
• Thyroid disease
• Autoimmune disease
• Diabetes (excluding gestational)
• History of eating disorder
• Currently taking antidepressants for < 6 months
• Currently taking antipsychotics
• Currently taking oral glucocorticoids (steroids, i.e. prednisone) for more than 6 months
• Currently breastfeeding
• Less than 6 months post-partum

Participants who are starting an IUD or implant through their provider could be eligible.