Glycemic Index and Brain Function

The Effects of Dietary Glycemic Index on Brain Function

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.

Study Overview

• Status: Completed
• Conditions: Obesity
• Intervention / Treatment: Other: Low GI; Other: High GI

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 Type: Interventional
• Enrollment (Actual): 12
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02215
      • Beth Israel Deaconess Medical Center
    • Boston, Massachusetts, United States, 02115
      • Children's Hospital Boston
    • Boston, Massachusetts, United States, 02215
      • Brigham and Women's Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 35 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: Male

Description

Inclusion criteria

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

Exclusion criteria

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Blood Flow in Brain Areas of Intake Control.	4 hours postprandial

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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	measuring metabolite profiles	Every 30 minutes for 5 hours.

Collaborators and Investigators

• Sponsor: Beth Israel Deaconess Medical Center
• Collaborators: Boston Children's Hospital; Brigham and Women's Hospital
• Investigators: Study Director: Belinda S Lennerz, MD, PhD, Boston Children's Hospital; Principal Investigator: David Alsop, PhD, Beth Israel Deaconess Medical Center

Publications and helpful links

General Publications

• Lennerz BS, Alsop DC, Holsen LM, Stern E, Rojas R, Ebbeling CB, Goldstein JM, Ludwig DS. Effects of dietary glycemic index on brain regions related to reward and craving in men. Am J Clin Nutr. 2013 Sep;98(3):641-7. doi: 10.3945/ajcn.113.064113. Epub 2013 Jun 26.

Study record dates

Study Major Dates

• Study Start: February 1, 2010
• Primary Completion (Actual): June 1, 2011
• Study Completion (Actual): September 1, 2011

Study Registration Dates

• First Submitted: February 5, 2010
• First Submitted That Met QC Criteria: February 5, 2010
• First Posted (Estimate): February 8, 2010

Study Record Updates

• Last Update Posted (Estimate): February 2, 2012
• Last Update Submitted That Met QC Criteria: February 1, 2012
• Last Verified: February 1, 2012

More Information

Terms related to this study

• Keywords: Weight Loss; Diet; Brain; Glycemic Index; Hunger; Intake Regulation
• Other Study ID Numbers: RA-003