Thermic & Lipemic Properties of Dietary Carbohydrates

Study Overview
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Brief Summary
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The purpose of this study is to determine if consumption of meals containing carbohydrates with different glycemic index (a high glycemic index meal and a low glycemic index meal)have different effects on energy expenditure, type of metabolic fuels used for energy, blood lipids and lipoproteins, and sensations of hunger, fullness, and the hormones related to satiety.

Detailed Description
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Little is known about the metabolic effects of chronic dieting and weight cycling in humans, but limited evidence suggests that fatty acid oxidation may be depressed leading to periodic elevation of circulating lipids associated with meal ingestion and preferential storage of fat in adipose tissue. With the traditional approach of restrictive dieting failing to result in permanent weight loss and, possibly producing abnormalities in lipid metabolism, it is important to evaluate alternative approaches to achieve a healthy body weight through improved metabolism. In this study the investigators will test the postprandial metabolic effects of standard mixed meals containing carbohydrates with high glycemic index and compare these effects to responses obtained with standard mixed meals, matched for protein and fat content but containing carbohydrates with low glycemic index.

Official Title
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Thermic & Lipemic Properties of Dietary Carbohydrates

Conditions
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Exogenous Obesity, Dietary Modification

Intervention / Treatment
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* Other: High Glycemic Index meals
* Other: Low Glycemic Index meals


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Body mass index between 25 and 30 kg/m2 Having regular menses Willing to refrain from restrictive dieting during the course of the study Exclusion Criteria: Pregnant or currently planning a pregnancy Cigarette smoking Taking medications to induce weight loss or change appetite History of cardiovascular disease History of metabolic disorders, including diabetes

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 48 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High Glycemic Index meals<br>Three days of run-in diet with meals containing high glycemic index carbohydrates followed by test day with breakfast meal containing high glycemic index carbohydrates. | Other: High Glycemic Index meals<br>* Dietary intervention with meals containing high glycemic index carbohydrates. All foods provided to meet the individual's energy needs. Standardized test meal (breakfast)also contained only high glycemic index carbohydrates and energy content was adjusted for each individual, providing 40% of daily energy needs.<br>* Other names: Low Fiber Meals;|
| Experimental: Low Glycemic Index meals<br>Three days of run-in diet with meals containing low glycemic index carbohydrates followed by test day with breakfast meal containing low glycemic index carbohydrates. | Other: Low Glycemic Index meals<br>* Dietary intervention with meals containing low glycemic index carbohydrates. All foods provided to meet the individual's energy needs. Standardized test meal (breakfast)also contained only low glycemic index carbohydrates and energy content was adjusted for each individual, providing 40% of daily energy needs.<br>* Other names: High fiber meals;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Respiratory Gas Exchange | Respiratory Gas Exchange will be measured using an automated metabolic cart. Gas analyzers and volumeter will be calibrated using manufacturer's procedures. | 30 minutes before a standardized test meal and intermittently for 480 minutes following the meal. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Plasma glucose | 1 fasting blood sample (0 minutes) and 9 post-prandial blood samples taken at 30, 60, 90, 120, 150, 210, 270, 360 and 480 minutes following consumption of standardized test meal. | 10 blood samples taken over a 480 minute period. | 
| Circulating lipoproteins | Blood samples for lipoprotein analyses were taken at fasting (0 minute) and at 150, 210, and 480 minutes following consumption of test meal. A subset of 10 randomly-selected subjects was chosen for this outcome measure | 4 blood samples taken over a 480 minute period | 
| Subjective evaluation of appetite | Visual analog scales were used to assess appetite-related sensations. Four responses were obtained during the fasting phase (120 minutes) and 12 responses were obtained in the 480 minute postprandial period. | 16 timepoints measured over 600 minutes | 
| Food consumption at a buffet-style meal | The amount and types of foods consumed were measured after subject was presented with a buffet-style meal. | at 480 minutes following test meal | 
| Body composition | Body composition (fat mass, % fat, lean mass, bone density) will be measured using dual energy x-ray absorptiometry. | measured the morning of the standard meal challenge | 
| Serum insulin | 1 fasting blood sample (0 minutes) and 9 post-prandial blood samples taken at 30, 60, 90, 120, 150, 210, 270, 360 and 480 minutes following consumption of test meal. | 10 blood samples taken over a 480 minute time period | 
| Plasma leptin | 1 fasting blood sample (0 minutes) and 9 post-prandial blood samples taken at 30, 60, 90, 120, 150, 210, 270, 360 and 480 minutes following consumption of test meal. | 10 blood samples taken over a 480 minute period | 
| Plasma ghrelin | 1 fasting blood sample (0 minutes) and 9 post-prandial blood samples taken at 30, 60, 90, 120, 150, 210, 270, 360 and 480 minutes following consumption of test meal. | 10 blood samples taken over a 480 minute time period | 
| Cholecystokinin (CCK) | 1 fasting blood sample (0 minutes) and 9 post-prandial blood samples taken at 30, 60, 90, 120, 150, 210, 270, 360 and 480 minutes following consumption of test meal. | 10 blood samples taken over a 480 minute time period | 
| GLP-1 | 1 fasting blood sample (0 minutes) and 9 post-prandial blood samples taken at 30, 60, 90, 120, 150, 210, 270, 360 and 480 minutes following consumption of test meal. | 10 blood samples taken over a 480 minute time period | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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energy metabolism, lipids, lipoproteins, satiety, glycemic load, insulin