This study is designed to investigate differences between people living with HIV (PLWHIV) and general populations on how the body utilises and stores energy. This study uses magnetic resonance imaging (MRI) to measure fat around the body organs including the heart and liver. The fat around body organs, also known as visceral fat, is known to be associated with metabolic syndrome and a risk factor for developing heart attacks and strokes. MRI scans are used frequently in hospitals to diagnose a range of conditions. These scans use radio waves to measure protons in body tissues. The machines can reconstruct tissues using complex algorithms to form composite images of body structures. MRI scans do not use ionising radiation and there is no risk to undertaking an MRI in terms of radiation. We often use MRI scans to assess the hearts' structure and function. In addition, we can use specific MRI sequences to assess the integrity of heart muscle. Heart MRI is often considered the gold standard imaging technique to assess the heart and heart muscle disease. This sub-study will use multiple MRI sequences to assess the heart and the liver. We are aiming to investigate any changes in heart and liver fat. In addition, we will assess any changes in fat levels within the heart muscle cells whilst also assessing for any change in the way the heart is functioning. PLWHIV have roughly double the risk of heart attacks compared to general populations. Previous studies have demonstrated that this increased risk may arise from the way in which fat is stored and metabolised in the body. We hope this study will give insight into why HIV-positive individuals have increased risks of heart attacks and how reducing visceral fat may reduce risk. It may lead to further medicines or treatment strategies to reduce the risk of heart attacks in HIV-positive individuals.