The overall objective is to investigate the effects of low and high glycemic index (GI)
meals varying in protein content on plasma glucose and insulin response, subjective ratings
of hunger, and subsequent food intake in twenty healthy, sedentary, overweight and obese men
and women between the ages of 21-65.
Each individual will participate separately in four testing sessions. Each testing session
will last for approximately 5 hours and will be separated by a minimum of one week.
Participants will arrive at the Temple University GCRC or CORE at either 7:30 a.m. or 8:30
a.m. after an overnight fast (10-12 hours) to ensure that all participants are in the same
metabolic state. Upon arrival the experimenter will ask participants to complete a
pre-session questionnaire and rate their feelings of hunger and satiety on a visual analog
scale (VAS). An indwelling catheter will be inserted in an antecubital vein by the study
nurse and a baseline blood sample will be obtained for measurement of glucose and insulin
concentrations. Glucose will be measured by the glucose oxidase method using a glucose
analyzer and insulin will be measured by radioimmunoassay.
One of four isocaloric meals (see example below), varying in macronutrient content and GI
value of foods, will be administered in random order at either 8:00 a.m. or 9:00 a.m. Energy
density will be controlled. The meal and 8 ounces of water will be consumed within fifteen
minutes. A short visual analog questionnaire will be distributed at the conclusion of the
meal to rate the meal consumed. Blood samples will be taken 15 minutes after food
consumption and at 30 minute intervals (i.e., 30, 60, 90, 120, 150, 180, 210, and 240
minutes) over four hours following administration of the meal. Four milliliters of blood
will be collected at each time point (via indwelling catheter), resulting in a total of 40
milliliters of blood collected at each study session and 160 milliliters (i.e., 40 ml x 4
testing sessions) within an 8 week time period. Participants will be asked to rate their
feelings of hunger at these time points. Following the last blood sample, participants will
be given the opportunity to consume food ad libitum from a buffet style lunch. Based on
known serving sizes and measurements of unconsumed food, the amount of food eaten and its
associated energy content will be determined.
- Men and women between the ages of 21-65 with a BMI of 25-40(kg/m2)
- Individuals who are currently dieting or restricting food intake and who report
pre-existing health afflictions such as diabetes, use of prescription medications,
use of appetite suppressants, or regular tobacco use will be excluded from the study
as they may affect appetite or impact the dependent measures of this study.