Comparison of Time-Restricted Feeding Versus Grazing

Study Overview
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Brief Summary
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The purpose of this pilot study is to find out what eating meals in a short time period early in the day (time-restricted feeding) versus eating meals spread out during the day (grazing) does to the body's ability to control blood sugar and to the health of its blood vessels. The investigators hypothesize that time-restricted feeding will be more effective at improving glucose tolerance and vascular condition (inflammation and micro- and macro-vascular function) than grazing.

Detailed Description
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Each participant will eat according to one of the two eating schedules (grazing or time-restricted feeding) for 5 weeks, have a 7-week washout period, and then eat according to the other eating schedule for 5 weeks. Measurements of glucose homeostasis and vascular condition will be performed before and after a participant follows each eating schedule.

Official Title
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Time-Restricted Feeding to Improve Glucose Tolerance and Vascular Condition

Conditions
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Prediabetes, Insulin Resistance, Vascular Diseases

Intervention / Treatment
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* Other: Time-Restricted Feeding
* Other: Grazing


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Are male Overweight: Have a body mass index between 25 and 50 kg/m^2 inclusive (a number calculated from height and weight) Are 35-70 years of age Have a hemoglobin A1C between 5.5 - 6.4% or prior medical indication of prediabetes Have a blood sugar level between 140 and 199 mg/dL two hours after drinking a sugary solution (OGTT) Have been eating dinner at least 8.5 hours after eating breakfast at least 90% of the time during the past year Have not fasted (go for a day without any food) more than 12 days total during the past year Be willing to eat most meals at Pennington Biomedical and/or under supervision Not eat any food other than that served by Pennington Biomedical Not drink any alcohol, juice, or other beverages that have calories other than what is served by Pennington Biomedical Keep water and no-calorie drinks like tea or diet soda the same during both of the timed eating periods Be willing to eat your meals according to the fixed schedules Exclusion Criteria: Have diabetes or are on anti-diabetes medication Have evidence of cardiovascular disease Suffer from significant cardiovascular, renal (kidney), cardiac (heart), liver, lung or nervous system disease Evidence of significant gastrointestinal issues or surgery that impacts nutrient absorption Regularly use medications such as steroids, beta blockers, and adrenergic-stimulating agents Are on any regular medicine that has not had the same dose for 1 month or longer Have a clinically significant abnormality as measured by a blood test Regularly drink alcohol (more than 2 servings per day) Have to do any kind of heavy physical activity Currently perform overnight shift work more than one day a week Are not able to eat only the food served to you by Pennington Biomedical, while in the study Are not able to stop drinking alcohol or other drinks with calories (e.g., soda, juice) other than what is served to you by Pennington Biomedical, while in the study

Ages Eligible for Study
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Minimum Age: 35 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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Male

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: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Time-Restricted Feeding (early in the day eating)<br>Participants will consume all meals early in the day and within a 6-hour window. | Other: Time-Restricted Feeding<br>* Time-restricted feeding is a variant of intermittent fasting that involves eating all of one's calories within a few hours each day (typically 4-9 hours), followed by a daily fast of 15-20 hours.<br>|
| Placebo Comparator: Grazing<br>Participants will eat meals spread out over the course of the day. | Other: Grazing<br>* Grazing involves eating meals spread out over the course of the day.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Glucose Tolerance | Glucose tolerance and indices of glucose homeostasis will be determined using an Oral Glucose Tolerance Test (OGTT). | Before and after 5 weeks on each feeding schedule | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Vascular Function | Macro- and micro-vascular function will be assessed by Radial Artery Applanation Tonometry and by Orthogonal Polarization Spectroscopy. The endpoints measured by these two tests include aortic blood pressure, arterial stiffness, capillary density, and red blood cell velocity. | Before and after 5 weeks on each feeding schedule | 
| Change in Inflammation and Metabolic Markers | Serum markers of inflammation, such as C-Reactive Protein (CRP) and inflammatory cytokines, and of metabolic processes will be measured (composite measure). | Before and after 5 weeks on each feeding schedule | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Time-restricted feeding, Intermittent fasting, Prediabetes, Insulin resistance, Glucose tolerance, Insulin sensitivity, Circadian rhythms, Diurnal