Glycemic Index and Brain Function

Sponsor

Beth Israel Deaconess Medical Center (Other)

Overall Status

Completed

CT.gov ID

NCT01064778

Collaborator

Boston Children's Hospital (Other), Brigham and Women's Hospital (Other)

Enrollment

Locations

Arms

Duration (Months)

Patients Per Site

0.2

Patients Per Site Per Month

Study Details

Study Description

Brief Summary

The investigators propose examine the effects of the dietary factor glycemic index (GI) on brain areas that control food intake and hunger. This knowledge could help design dietary approaches that decrease hunger, and thus promote new weight loss strategies.

Condition or Disease	Intervention/Treatment	Phase
Obesity	Other: Low GI Other: High GI	N/A

Detailed Description

Most individuals have great difficulty following reduced calorie diets because they experience increased hunger. This process is regulated by specific brain areas. Though many psychological and environmental factors are involved, physiological effects of diet may have a significant impact. The postprandial rise in blood glucose, quantified by the glycemic index (GI), is of particular interest. High GI meals elicit hormonal events that limit availability of metabolic fuels, causing hunger and overeating, especially in people with high insulin secretion.

Our aim is to examine how postprandial changes after high versus low GI meals affect hunger and brain function in areas of intake control. Specifically, we speculate that obese individuals will demonstrate functional changes in brain areas of intake control and increased hunger after a high versus low GI meal.

We will recruit obese, young adults and quantify their insulin secretion during a 2-hour oral glucose tolerance test. A brief practice MRI session will serve to familiarize the subjects with the scanning process. During the two test sessions, standardized test meals with high versus low GI will be given in a randomized, blinded cross-over design. Serial blood levels of hormones, metabolic fuels, and metabolites will be correlated with perceived hunger, and a perfusion MRI scan will be performed to assess brain activation during the late postprandial phase, at the nadir of blood sugar and insulin levels (4 hours postprandial).

This work will inform an integrated physiological model relating peripheral postprandial changes to brain function and hunger. In addition, findings may provide evidence of a novel diet-phenotype, in which baseline clinical characteristics can be used to predict which weight loss diet will work best for a specific individual. Metabolite profiling might shed light on the mechanisms linking diet composition to brain function, and provide feasible clinical markers of the identified phenotype to facilitate translation into practice.

Study Design

Study Type:

Interventional

Actual Enrollment :

12 participants

Allocation:

Randomized

Intervention Model:

Crossover Assignment

Masking:

Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)

Primary Purpose:

Treatment

Official Title:

The Effects of Dietary Glycemic Index on Brain Function

Study Start Date :

Feb 1, 2010

Actual Primary Completion Date :

Jun 1, 2011

Actual Study Completion Date :

Sep 1, 2011

Arms and Interventions

Arm	Intervention/Treatment
Active Comparator: Low GI	Other: Low GI Subjects will be instructed to consume a liquid test meal with a low GI over 5 minutes after baseline laboratory evaluations. The low and high GI meal contain similar amounts of milk, oil, dried egg whites, equal, and vanilla extract. The low GI meal corn-starch as a carbohydrate. Both meals have similar macronutrient composition (60% carbohydrate, 15% protein, 25% fat), micronutrient profiles, physical properties, palatability and sweetness. The high vs. low GI meals have a predicted difference in GI of 90 vs. 40, and consistent with this prediction, a pilot study in obese young adults found a 2.2-fold difference in glycemic response (p<0.001). The test meals will provide 25% of individual daily energy requirements.
Experimental: High GI	Other: High GI Subjects will be instructed to consume a liquid test meal with a high GI over 5 minutes after baseline laboratory evaluations. The low and high GI meal contain similar amounts of milk, oil, dried egg whites, equal, and vanilla extract. The high GI meal contains corn-syrup as a carbohydrate. Both meals have similar macronutrient composition (60% carbohydrate, 15% protein, 25% fat), micronutrient profiles, physical properties, palatability and sweetness. The high vs. low GI meals have a predicted difference in GI of 90 vs. 40, and consistent with this prediction, a pilot study in obese young adults found a 2.2-fold difference in glycemic response (p<0.001). The test meals will provide 25% of individual daily energy requirements.

Arm

Intervention/Treatment

Active Comparator: Low GI

Other: Low GI

Subjects will be instructed to consume a liquid test meal with a low GI over 5 minutes after baseline laboratory evaluations. The low and high GI meal contain similar amounts of milk, oil, dried egg whites, equal, and vanilla extract. The low GI meal corn-starch as a carbohydrate. Both meals have similar macronutrient composition (60% carbohydrate, 15% protein, 25% fat), micronutrient profiles, physical properties, palatability and sweetness. The high vs. low GI meals have a predicted difference in GI of 90 vs. 40, and consistent with this prediction, a pilot study in obese young adults found a 2.2-fold difference in glycemic response (p<0.001). The test meals will provide 25% of individual daily energy requirements.

Experimental: High GI

Other: High GI

Subjects will be instructed to consume a liquid test meal with a high GI over 5 minutes after baseline laboratory evaluations. The low and high GI meal contain similar amounts of milk, oil, dried egg whites, equal, and vanilla extract. The high GI meal contains corn-syrup as a carbohydrate. Both meals have similar macronutrient composition (60% carbohydrate, 15% protein, 25% fat), micronutrient profiles, physical properties, palatability and sweetness. The high vs. low GI meals have a predicted difference in GI of 90 vs. 40, and consistent with this prediction, a pilot study in obese young adults found a 2.2-fold difference in glycemic response (p<0.001). The test meals will provide 25% of individual daily energy requirements.

Outcome Measures

Primary Outcome Measures

Blood Flow in Brain Areas of Intake Control. [4 hours postprandial]

Secondary Outcome Measures

Subjective Hunger Rating [Every 30 minutes for 5 hours.]
Blood Glucose Level [Every 30 minutes for 5 hours.]
Blood Insulin Level [Every 30 minutes for 5 hours]
Blood Glucagon Level [Every 30 minutes for 5 hours.]
Blood Growth Hormone Level [Every 30 minutes for 5 hours.]
Blood Epinephrine Level [Every 30 minutes for 5 hours.]
Blood Fatty Acids Level [Every 30 minutes for 5 hours.]
measuring metabolite profiles

Eligibility Criteria

Criteria

Ages Eligible for Study:

18 Years to 35 Years

Sexes Eligible for Study:

Male

Accepts Healthy Volunteers:

Yes

Inclusion criteria

Males age 18 to 35 years
BMI less than or equal to 25 for age and gender

Exclusion criteria

weight > 300 lbs
largest body circumference > 144cm
body shape incompatible with MRI scanner or equipment
MRI exclusion criteria
large fluctuations in body weight (5% over preceding 6 months, 2.5% during the study)
known medical problems that may affect metabolism or hormones
diabetes mellitus (fasting plasma glucose ≥126 mg/dL)
other abnormal laboratory screening tests
taking any medications or dietary supplements that might affect body weight, appetite, or energy expenditure
smoking or illicit substance abuse
high levels of physical activity (>30 minutes per day, > 4days per week)
currently following a weight loss diet
allergies or intolerance to eggs, vanilla extract, equal, canola oil, milk, cornstarch, corn syrup

Contacts and Locations

Locations

	Site	City	State	Country	Postal Code
1	Children's Hospital Boston	Boston	Massachusetts	United States	02115
2	Beth Israel Deaconess Medical Center	Boston	Massachusetts	United States	02215
3	Brigham and Women's Hospital	Boston	Massachusetts	United States	02215