Abstract. The prevalence of insulin resistance, type II diabetes, obesity and co-morbidities of the metabolic syndrome is rising. More than 120M US adults are living with diabetes or are pre-diabetics. This carries a huge financial burden, which was estimated at ~$404B in 2019. Visceral fat (but not subcutaneous) and specifically the mesenteric fat, was shown to have a major role in the pathophysiology of insulin resistance and diabetes. Fat cells are more sensitive to low temperatures compared to any other cell type. Fat solidifies at a higher temperature than the freezing temperature of water, forming needle like structures that promote cell death. Induction of fat cell death by low temperatures (cryolipolysis) is already detected at a temperature of +100C. This relatively high temperature is making cryolipolysis an attractive approach to induce mesenteric fat mass loss as a new treatment modality to reduce Insulin resistance and diabetes in patients with visceral obesity. Our objective is to test the feasibility and safety of a novel approach and device to reduce the mass of the mesenteric fat using cold temperatures, as a new treatment option to reverse insulin resistance and the incidence of diabetes. Hypothesis: excessive mesenteric fat is a major contributor to the progression of insulin resistance, diabetes, and the metabolic syndrome. Cold temperatures delivered into the mesenteric fat will promote fat cells loss without injuring surrounding tissues and without any significant side effects. The decrease in mesenteric fat will have beneficial effects on insulin resistance, diabetes progression, and the metabolic syndrome. To test our hypothesis, we propose the following Specific Aims: 1A. To utilize computational heat transfer methods based on Finite Element Analysis (FEA) to model fat thermal cycle for different device temperatures, shapes, materials, and treatment duration. 1B. To validate acute safety and thermal cycle to be used in in-vivo chronic safety and feasibility studies (Aim 2). 2. In the Ossabaw pig model of insulin resistance, to evaluate the safety and feasibility of mesenteric fat cryolipolysis on insulin resistance progression. Milestones: Successfully modeling the thermal cycle in visceral fat will be considered as a first milestone. Building a cryolipolysis prototype device and in vivo validation of tissue temperatures calculated in 1A will be the second milestone. Seven days post-procedure survival without complications will be considered as the third milestone. Successfully and safely reducing the mesenteric fat mass and reversing the progression of insulin resistance (Aim 2) will be the fourth milestone. The successful completion of these studies will show that cryolipolysis of mesenteric fat is a safe and effective way to treat insulin resistance. The device developed, and the results obtained, will pave the way for optimal device design and safety and efficacy studies utilizing envisioned protocols to be even...