Diabetes is a major risk factor for heart failure. Moreover, patients with diabetes and heart failure have a worse survival than those without diabetes. We know that patients with diabetes have altered heart metabolism, structure, and function. It is unclear if these alterations can be ameliorated with weight loss. We would like to learn whether cardiac metabolism, structure, and function in diabetic patients with heart failure symptoms can be improved with marked weight loss after gastric bypass surgery.

Study Day 1. Screening. We will screen subjects with known diabetes or those with a high likelihood of diabetes who will undergo gastric bypass surgery. We will approach all patients at the Bariatric Surgery clinic regarding enrollment in our study. If they agree to participate, they will answer simple questionnaires re: medical history, obesity information, and MRI/MRS exclusion (see Appendices). We will obtain their permission to review their medical charts.

Study Day 2. Screening will include a physical examination and phlebotomy for a complete blood count, oral glucose tolerance test, \& comprehensive metabolic profile and a screening rest and stress echocardiogram. The rest and stress echocardiogram will be used to exclude cardiac abnormalities other than diastolic dysfunction. Optison™ or Definity will be used as needed for the echocardiograms. We will determine the subjects' fat and fat-free mass using dual-energy X-ray absorptiometry (DXA) imaging at the Center for Applied Research Sciences unit.

Study Day 3. Baseline Imaging Studies. Subject preparation. We expect 30 subjects to complete our study's screening tests and meet our study criteria. The evening before imaging Study Days 3 \& 4, subjects will be admitted to The Center for Applied Research Sciences Intensive Research Unit in order to standardize their metabolic milieu for their myocardial fat imaging studies. At 1800, subjects will ingest a standard meal containing a total of \~700 kcal for the subjects. Carbohydrate, fat, and protein will represent 55, 30, and 15%, respectively, of total energy intake. At 2000, subjects will ingest a defined liquid formula snack containing 250 kcal, 40 g carbohydrate, 6.1 g fat, and 8.8 g protein (Ensure, Ross Laboratories, Columbus, OH). After this snack, all subjects will fast until completion of the study the following day. Subjects will be given a lunch after completing their imaging studies. Magnetic resonance imaging (MRI). Subjects will be placed in the gantry of the scanner. Examinations will be performed on the 1.5T scanner using ECG gating, breath-hold, and a chest array coil This same scanner will be used for 1H-Magnetic resonance spectroscopy (MRS). The MRS protocol is based on a free-breathing, point-resolved spectroscopy (PRESS) sequence with both ECG and two-dimensional respiratory gating optimized for accuracy and robustness. Subject care. All subjects will be given a lunch, prepared at the Intensive Research Unit after imaging is completed. All imaging should be completed by 12PM. If the physician monitoring the subject determines that the subject would benefit from furosemide 20mg, p.o. x 1, or KCl, p.o. - a 10 day course may be provided (with a follow-up K+ check). Patients' physicians would be notified of any changes. We request subjects stay on their same medical regimen throughout the testing period. We recognize that this may not be possible for all subjects.

Gastric bypass. Subjects will undergo surgery after Study Day 3. The same surgeon (J.C.E.) will perform all bypass procedures using standard techniques. Briefly, a small (\~20 mL) proximal gastric pouch will be created by stapling across the stomach, and a 150 cm Roux-Y limb constructed by transecting the jejunum 30cm distal to the ligament of Treitz and creating a jejunojejunostomy 150 cm distal to the transection.

Study Day 4. Imaging Studies - 3 months after surgery. Subjects will undergo the same imaging studies under the same conditions and in the same order as on Study Day 3 except that subjects on Day 4 will also undergo a resting echocardiogram for diastolic function.