Effects of Caffeinated and Decaffeinated Coffee on Body Weight and Glucose Tolerance

Study Overview
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Brief Summary
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Habitual consumption of coffee may have substantial beneficial effects on glucose metabolism according to recent findings of epidemiological studies in the U.S., Europe, and Japan. However, data from longer-term human intervention studies with appropriate outcome measures are lacking. We will study the effects of caffeinated and decaffeinated coffee consumption on body fatness, insulin sensitivity and glucose tolerance that may underlie the observed associations with a lower risk of type 2 diabetes in a randomized controlled trial. We hypothesize that both caffeinated and decaffeinated coffee will improve insulin sensitivity and glucose tolerance. Before starting a larger, long-term intervention study, we will conduct a pilot study to test the feasibility of such a trial. The pilot study will be an 8-week parallel trial in 45 overweight individuals, who will be randomized to drinking 5 cups per day of 1) caffeinated coffee (n=15), 2) decaffeinated coffee (n=15), or 3) water (n=15). Body fatness (weight, waist circumference, bioelectrical impedance), insulin sensitivity (HOMA model), and glucose tolerance (oral glucose tolerance test) will be the primary outcomes. We will assess the adherence of participants to their assigned treatment by measuring serum caffeine concentrations, documentation of coffee use in diaries by the participants, and counting unused coffee packets. We will also obtain feedback from participants on how to improve compliance in a future trial. If successful, this study will form the basis for a definitive trial of coffee consumption, body fatness, and glucose tolerance. Given the extensive use of coffee and the rapidly increasing health burden of type 2 diabetes, such a trial would have important public health implications.

Detailed Description
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Habitual consumption of coffee may have substantial beneficial effects on glucose metabolism according to recent findings of epidemiological studies in the U.S., Europe, and Japan. However, data from longer-term human intervention studies with appropriate outcome measures are lacking. We will study the effects of caffeinated and decaffeinated coffee consumption on body fatness, insulin sensitivity and glucose tolerance that may underlie the observed associations with a lower risk of type 2 diabetes in a randomized controlled trial. We hypothesize that both caffeinated and decaffeinated coffee will improve insulin sensitivity and glucose tolerance. Before starting a larger, long-term intervention study, we will conduct a pilot study to test the feasibility of such a trial. The pilot study will be an 8-week parallel trial in 45 overweight individuals, who will be randomized to drinking 5 cups per day of 1) caffeinated coffee (n=15), 2) decaffeinated coffee (n=15), or 3) water (n=15). Body fatness (weight, waist circumference, bioelectrical impedance), insulin sensitivity (HOMA model), and glucose tolerance (oral glucose tolerance test) will be the primary outcomes. We will assess the adherence of participants to their assigned treatment by measuring serum caffeine concentrations, documentation of coffee use in diaries by the participants, and counting unused coffee packets. We will also obtain feedback from participants on how to improve compliance in a future trial. If successful, this study will form the basis for a definitive trial of coffee consumption, body fatness, and glucose tolerance. Given the extensive use of coffee and the rapidly increasing health burden of type 2 diabetes, such a trial would have important public health implications.

Official Title
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Effects of Caffeinated and Decaffeinated Coffee on Body Weight and Glucose Tolerance

Conditions
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Overweight

Intervention / Treatment
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* Dietary Supplement: Decaffeinated coffee
* Dietary Supplement: Caffeinated coffee
* Dietary Supplement: No coffee


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Aged at least 18 years with an ability and willingness to give written informed consent. Body mass index 25-35 kg/m2 Users of at least 2 cups of caffeinated coffee per day who are willing to be randomized to any of the interventions. Non-smoking Exclusion Criteria: Any condition/illness that may affect the study outcomes or would make participation potentially harmful such as pregnancy or breastfeeding, diabetes mellitus, heart disease, stroke, hypertension, malabsorption syndromes, Gastroesophageal reflux disease GERD, a history of ulcer, according to a detailed medical history. Abnormal hepatic function (liver function test > twice the normal range), abnormal renal function (creatinine > 1.1 mg/dl), fasting plasma glucose in the diabetic range (>/= 126 mg/dl), or blood pressure > 140/90 mmHg. Present alcoholism or drug abuse or use of medications that could interfere with the treatment including bronchodilators, quinolone antibiotics, monoamine oxidase inhibitors, anxiolytics, ranitidine, corticosteroids, growth hormone, antihypertensives.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

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: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Caffeinated coffee<br>Caffeinated coffee | Dietary Supplement: Caffeinated coffee<br>* 5 cups per day for 8 weeks<br>* Other names: Instant Nestle caffeinated coffee;|
| Experimental: Decaffeinated coffee<br>Decaffeinated coffee | Dietary Supplement: Decaffeinated coffee<br>* 5 cups per day for 8 weeks<br>* Other names: Instant Nestle decaffeinated coffee;|
| Active Comparator: No coffee<br> | Dietary Supplement: No coffee<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| glucose tolerance / insulin sensitivity |  | 4 and 8 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| body weight/fatness, blood pressure, concentrations of blood lipids, adipokines, inflammatory markers |  | 4 and 8 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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coffee, caffeine, glucose tolerance, body weight, insulin sensitivity, randomized controlled trial