Anaemia is one of the major nutritional problems that brings many negative health consequences to women's health, especially during pregnancy. There was growing evidence that overweight/obesity can lead to anaemia. However, the association between anaemia and overweight/obesity has not been fully established, especially in developing countries, including Indonesia. The prevalence of overweight/obesity has sharply increased in Indonesia for the past decades, while anaemia prevalence did not show a significant decrease. The prevalence of anaemia in Indonesia was still alarming, with 27.2% in nonpregnant women and 48.9% in pregnant women (Indonesia MoH, 2019a). Therefore, the study of the association between overweight/obesity and anaemia among women of reproductive age in Indonesia needs to be conducted using appropriate measurements. Furthermore, previously available studies highly ignored the role of dietary intake in the association between overweight/obesity and anaemia despite its importance. This study will also measure dietary intake among women.

Once participants agree to participate in this study, the investigators will ask questions about themselves (latest education history, employment, general health, menstrual history, smoking history, and physical activity level). The investigators will then ask the participants to write the food and beverages consumed in the dietary record form for 3-non consecutive days. Then, the investigators will ask about their dietary intake in the last 24 hours/1 day (foods the participants have taken and their approximate amount). After that, the investigators will take anthropometric measurements (height, weight, and waist circumference) to define nutritional status. The investigators will also collect a small amount (3mL) of blood samples from the participants, two times (before and after intervention). Blood collection will be performed by trained nurses/medical analysts under a medical doctor\&amp;#39;s supervision and collected at the university clinic. The investigators will measure several parameters from that blood sample, such as iron status parameters (including hemoglobin, serum ferritin, and hepcidin) and other chemicals in the blood that indicate inflammation (AGP and CRP). The results of these tests will be provided to all participants.

After collecting these data, participants will be assigned to one of the two study groups using matching criteria (age, education level, and occupation). Participants in all groups will receive iron supplements. The participants will not be made aware of which arm they have been assigned to. For the following three months, the participants will receive approximately 90 iron supplements to be consumed every day. The study staff will contact the participants through short messages and monthly visitation to ensure adherence to iron supplement consumption. After three months, the investigators will stop providing iron supplements. The investigators will collect information about their dietary intake over the last day and retake their anthropometry measurements. The investigators will also collect blood samples from participants and perform the same test as the previous one.

The investigators have asked the subjects to participate in this study because the participants are women aged between 20 and 29 years, neither pregnant nor lactating, living in this area, are healthy, have not received any micronutrient supplementation in the last three months, and have not undergoing body mass reduction or on any particular weight loss diet. After anthropometric screening, each participant will be assigned to a case or control group based on the Body Mass Index (BMI) results.