This study is designed to gain a better understanding of meal viscosity and the utility of dietary sources of viscous polysaccharide fibers to modulate postprandial metabolic and satiety mechanisms in pre- and post- menopausal overweight women in order to optimize acute metabolic responses to meals as well as most favorably affect appetite, food intake and overall body weight control.
Objectives of this study include:
1. To investigate the effects of viscous polysaccharide type fibers in a meal on postprandial intestinal-phase mechanisms of satiety \[eg., cholecystokinin (CCK)\] and meal-associated metabolic (eg., glucose, insulin, triglyceride) response patterns to low glycemic index (GI), fiber-controlled preload meals compared to a low fiber, high GI meal in overweight pre- and post- menopausal women.
2. To characterize the subjective and behavioral satiety responses to study-specific preload meals varying in viscous fiber content as well as determine the relationship of these satiety responses to the preload-associated physiological responses in overweight pre- and post- menopausal women.
3. To examine the influence of menopausal status of overweight women on the physiological, subjective and behavioral responses to study preloads.
The study is a randomized, 3-arm, 6-sequence, within-subjects, crossover, treatment-controlled study utilizing a repeated measures, multiple sampling paradigm to evaluate the metabolic and satiety response pattern to low glycemic index (GI) fiber-controlled preload treatments differing in viscous fiber content compared to a high GI preload meal.
The study will test 3 isocaloric treatment preloads in relatively healthy overweight, mildly obese, pre- and post- menopausal women. Preload meals will be prepared as breakfast meals using muffins and yogurt beverage / shake as the base for which glycemic index (GI) of the meal, including fiber / viscous fiber content, will be manipulated. All preloads have been matched as close as possible on sensory qualities as well as macronutrient composition, fiber and energy content and volume.
The 3 treatments will include as fiber source either viscous polysaccharide fiber source, eg., psyllium husk, and insoluble non-viscous producing fiber source, eg., cellulose, respectively. These fibers are commercially available.
Preload meals will be prepared to contain about 1 kcal/g offered as a 600 kcal meal portion. The macronutrient distribution for fat, carbohydrate and protein will be 30%, 55% and 15% of energy, respectively. Fiber will be included at 2 levels: 2 g/100 kcal for the 2 fiber containing preload meals and no fiber for the high GI low fiber control. These levels of fiber are consistent with our previously studied breakfast meals and for the higher fiber meals, just above the recommended intake for adult Americans. Preload meals will be matched as closely as possible on micronutrients and sensory (palatability, sweetness, texture) quality.
Preload meals be provided under fasting conditions and consumed within 20 minutes. Subsequent food intake will be measured in lab at a test meal and then by food records at home thereafter.
Subjects will receive each preload meal in random order \~ 1 month apart in order to standardize cyclic phase within the pre-menopausal group. Each preload test session will include collection of food records and menstrual logs, in-lab preload and test meal consumption, multiple blood sampling and visual analog scale completion.
Blood sample collection and visual analog scale (VAS) completion will occur before (fasting, time 0) preload meal consumption and then at 20, 40, 60, 90, 120, 150, and 180 min thereafter. A test meal lunch will be offered 2.5 h post-preload meal consumption. Test meal will be provided ad libitum. Final two blood draws and satiety evaluation will occur after lunch (210 and 240 minutes).
Blood will be measured for glucose, insulin, triglycerides and CCK at the specific time periods listed above. Occuring at the same time period, the subject will complete the VAS, a validated method for assessing subjective measures of appetite. Subjects will also rate the preload meals using the VAS on a number of sensory qualities to assess palatability.
