RecruitingFeasibility of Adipose Tissue Triglyceride (TG) Labelling in Familial Partial Lipodystrophy (FPLD)Background: People with familial partial lipodystrophy (FPLD) do not store fat in the body normally. This can lead to serious illnesses such as diabetes and heart disease. To learn more about FPLD, researchers want to compare the fat tissue in people with this disease to the fat tissue of healthy people. Objective: To collect and analyze samples of fat tissue in people with and without FPLD. Eligibility: People aged 18 to 65 years with FPLD. Healthy adults are also needed. Design: Participants will be screened. They will have a physical exam. The size and shape of their body will be measured. They will have an imaging scan to measure their bones, muscle, and fat. Participants will be given heavy water to drink at home. The water contains a tracer to help measure the fat in their blood. They will drink 1 vial 3 times a day. After drinking the water for 9 days, participants will come to the clinic for a 3-day stay. They will eat only foods provided by the hospital; the foods will contain tracers. A needle will be inserted into a vein in the arm; participants will receive infusions of other tracers through this needle into their blood; this needle will also be used to draw blood samples for testing. On their third day in the clinic, participants will have biopsies: Small samples of fat will be removed from under the skin on the belly and thigh. Participants may return for a follow-up visit 8 days after leaving the clinic. Blood draws and fat tissue biopsies will be repeated.