Supplemental Calcium in Overweight Out-Patients

Detailed Summary

This study will examine the health effects of calcium supplements in overweight adults. Overweight adults often eat a diet low in calcium. Some studies have found low calcium intake in people who have some of the medical problems often seen in overweight adults. This study will see if extra calcium improves the health of overweight adults. Volunteers in general good health 18 years of age or older who are overweight (body mass index equal to or greater than 25 kilograms per square meter of body surface) may be eligible for this study. Women who are pregnant or breastfeeding may not participate. The study includes four visits, described below. Visit 1 Volunteers will be screened for participation in the study with a medical history, physical examination, and blood and urine tests. At home, they will collect a 24-hour urine sample; fill out questionnaires to assess their average calcium intake; and record their food intake for 7 days. Those enrolled in the study will continue with the next 3 visits. Visit 2 Participants will complete a physical activity questionnaire, have their food diary reviewed, and meet with a dietitian for nutritional counseling. Triceps fold thickness and waist and hip circumferences will be measured three times. Body composition will be analyzed by a DEXA study. For this procedure, the subject lies on a flat table while a small dose of X-rays is passed through the body. Participants will be randomly assigned to take either calcium carbonate (1500 mg/day) or placebo capsules twice a day by mouth for 2 years. (The placebo looks like the calcium capsules but contains no calcium.) They will receive a 6-month supply of study capsules during visit 2 and return to NIH every 6 months for the next supply. They will also be sent questionnaires by mail every 3 months to complete information about health problems and how often the study capsules are being taken. Visits 3 and 4 Visit 3 is scheduled after participants have taken the study capsules for 1 year; visit 4 is scheduled after 2 years (the end of the study). At each of these visits, participants will have a DEXA scan, blood and urine tests, blood pressure measurements, and measurements of height, weight, waist and hip circumference. They will complete questionnaires about their medical history, side effects of the study medications, dietary calcium intake, and physical activity, and they will meet with one of the study investigators to talk about any concerns regarding the study. At the fourth visit, participants will answer some additional questions about their study participation and return the Diet History Questionnaire that was mailed to them before the visit.

Study Details

Timeline

Interventions