; will be eumenorrhoeic or using the combined oral contraceptive pill, an intrauterine system, or intrauterine device; be weight stable, defined as no change in self-reported body mass ≥ 5% over the previous 3 months; have a BMI between 18 and 30 kg·m, and; not be pregnant or lactating.
Regular and Reserve military servicewomen, and female civilians, will be invited to volunteer. Individuals interested in particpating will contact the investigators, upon which they will recieve a Participant Information Sheet and be invited to a phone conversation. The study aims, requirements, right to withdraw, and risks will be outlined. This study has received favourable ethical opinion from the Ministry of Defence Research Ethics Committee .