Fat Cell Size in Insulin Resistance

Study Summary

This study, conducted at Stanford University in Palo Alto, California, will examine how insulin metabolism and cardiovascular risk are altered in response to weight loss. Insulin is a natural hormone that causes cells to remove glucose (sugar) from the blood. People who are insulin-sensitive remove glucose efficiently. People who are insulin-resistant require more insulin to remove glucose from the blood. Adult volunteers will be recruited for this study through advertisements in local newspapers in communities around Stanford University. Participants will undergo the following tests and procedures: * Insulin sensitivity testing: Before beginning the study, participants will be tested for insulin sensitivity. For the test, two small catheters (plastic tubes) are placed into two veins - one for infusing glucose, insulin, and sandostatin (a drug that blocks insulin secretion from the pancreas), and one for drawing blood samples. The infusions are done over 3 hours. Blood samples are collected before, during, and at the end of the study to measure how well the cells remove glucose from the blood in response to insulin. * Research diet: Participants are assigned to a low-calorie diet tailored to the individual's metabolic rate. The diets contain either 40 or 60 percent of total calories as carbohydrates, 40 or 20 percent as fat, and the rest as protein. People with type 2 diabetes who are taking diabetes medicine with have a diet of 45 to 50 percent carbohydrates, 35 to 40 percent fat, and the rest protein. * Meal profile: Before beginning the diet and after 4 months on the diet, participants are tested for the effects of the various study diets on control of blood sugar and fats. On the day of each test, participants have a physical examination and provide a medical history. Then, a small catheter is placed in a vein. Blood samples are drawn before breakfast and then hourly for up to 8 hours. * Participants who are diabetic are randomly assigned to take one of three