The objective of this study is to investigate whether nutritional supplementation with magnesium can improve cardiovascular structure and function in participants with obesity - with a long-term goal of preventing clinical heart failure. Specifically, in a randomized open-label pilot study, we will assess whether dietary Magnesium (Mg) supplementation (versus no supplementation) for 24 weeks in obese patients will improve left ventricular (LV) mass.

The investigators propose a 24-week therapeutic trial involving 40 participants with obesity from the Providence VA Medical Center without clinical heart failure. 20 participants will be treated with 400 mg of Magnesium Oxide twice daily, while 20 participants will receive no treatment. The trial tests the hypothesis that oral Mg supplementation will improve: LV structure (by LV mass, steatosis, and ECV), LV function (systolic and diastolic), vascular health (systolic blood pressure and aortic pulse wave velocity) and visceral adiposity.

Inclusion Criteria:

Body mass index greater than 30 kg/m2

Exclusion Criteria:

1. History of hospitalization for heart failure (systolic or diastolic);
2. Unstable angina or prior myocardial infarction;
3. LV ejection fraction <50% on imaging study;
4. Valvular heart disease (stenosis or insufficiency) greater than moderate degree;
5. Renal dysfunction, serum creatinine >2.5 mg/dL or estimated creatinine clearance <30 mL/min/1.73 m2 (30),
6. Pregnant women or actively breastfeeding women
7. History of drug supplementation within the last 6 months in which more than 50 miliequivalents per day of supplemental magnesium is contained