The Effects of Orange Juice on Insulin Sensitivity and Plasma Lipids

The aim of this study is primarily to investigate the ability of antioxidants found in orange juice (OJ) to increase the body's sensitivity to the hormone insulin. Overweight or mildly obese women, who are otherwise healthy, will be recruited. The time commitment for subjects is \~14wks. Subjects will attend the laboratory on 5 occasions after fasting from midnight. The 1st is a medical screening. Laboratory visits 2 \& 5 will take \~5hrs and will be separated by 3 months, during which time subjects will consume 250ml of an orange drink (either OJ or an orange flavoured control drink) once a day. During visits 2 \& 5, subjects will have a scan to assess their %body fat using a low-dose x-ray machine, and have their insulin sensitivity measured using a technique called a 'Glucose Clamp'. During the 3hr glucose clamp, subjects receive an infusion of the hormone insulin and a glucose solution directly into their blood stream, with insulin sensitivity determined from the amount of glucose required to maintain blood glucose at normal levels. In addition, a small sample of fat tissue (about the size of a haricot bean) will be taken from underneath the skin of the belly. Subjects will record their food intake for 3-days in weeks 3, 7 and 11 of consuming the drink, and come to the lab for visits 3\&4 during weeks 4\&8. Laboratory visits 3\&4 repeat measurements taken in the 1st (screening) visit.