Early on, Pories ran a study to rule out the effect of diet. To do this, he compared patients who had gastric bypass surgery with patients who tried to lose weight through diet alone. When diabetic patients diet alone, insulin resistance lessens, but it doesn't disappear. A current trial of a different surgical procedure for morbid obesity may offer further evidence. Gastric banding cinches the stomach to allow less food to pass through, but unlike the gastric bypass, it does not change the basic physiology of the digestive system.
Food continues to pass through the entire stomach and intestine.
As gastric banding patients return for one-year checkups, their progress will be compared with that of bypass patients. If bypass patients again show superior fitness, it will give diabetes researchers more reason to focus tightly on hormonal signals originating in the gut. Progress also is coming on the cellular front, where advances in knowledge are measured in increments. The researchers, for example, have narrowed in on at least one factor contributing to insulin resistance, the overabundance of an enzyme that appears to block cells from absorbing glucose in response to insulin. To prove their theory, they have developed a mouse in which they can control the amount of the enzyme being produced.