Inherited and Environmental Risks Acting on Body Weight (INTERACT)

Genetic and Environmental Contributions to Obesity Pathogenesis

The goal of this research is to investigate genetic and environmental factors that contribute to obesity through brain inflammation. The main questions are 1) if identical twins, who differ in food consumption habits, have differences in adiposity markers and brain inflammation and 2) if signs of brain inflammation in response to a specific diet is modified by genetics.

Study Overview

• Status: Not yet recruiting
• Conditions: Obesity; Genetics
• Intervention / Treatment: Behavioral: Diet modification

Detailed Description

In study 1, participant twin pairs that differ in habitual diet intake, will complete an in-person study visit that includes an MRI of the brain and abdomen, body composition measurement, a blood draw and questionnaires. In study 2, a different set of participant twin pairs will complete 3 in-person study visits over 2 weeks, during which all meals will be provided by the study. Visits will include brain MRI, body composition measurements, blood draws and questionnaires.

• Study Type: Interventional
• Enrollment (Estimated): 110
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: INTERACT Study; Phone Number: 206-616-6360; Email: interactstudy@uw.edu

Study Locations

• United States
  • Washington
    • Seattle, Washington, United States, 98109
      • University of Washington
      • Contact: INTERACT Study; Phone Number: 206-616-6360; Email: interactstudy@uw.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age 20-45 years
• Differs in habitual diet from co-twin (study 1).
• Willing to undergo 7-day overfeeding and hypocaloric feeding periods (study 2)
• Member of the Washington State Twin Registry

Exclusion Criteria:

• History of bariatric surgery or active participation in weight-loss program
• Major medical or neurological disorder (e.g., diabetes, multiple sclerosis)
• Known gallbladder disease, anemia, impaired thyroid, kidney or liver function or hypertriglyceridemia (>350 mg/dl) (study 2)
• Current use of weight-loss medications or other medications known to alter appetite (e.g., atypical anti-psychotics)
• High levels of vigorous physical activity (>300 min./week)
• Pregnancy, menopause, or breastfeeding
• Individuals with severe food allergies and dietary restrictions (e.g., vegan/vegetarian, gluten-free, others) (study 2)
• Co-twin unwilling or unable to participate
• MRI contraindication (e.g., implanted metal, claustrophobia)
• Lifetime eating disorder
• Current smoking or heavy alcohol use (≥ 2 drinks per day for females and ≥ 3 drinks per day for males)
• BMI > 45 kg/m2 (study 1)
• BMI > 35 kg/m2 (study 2)
• Weight > 350 pounds or determined to be safe by MRI tech (MRI limit)
• Inability to participate in a controlled diet program (study 2) or undergo other study procedures
• Non-English speaking-or-reading individuals

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
No Intervention: Study 1, A co-twin control study of habitual diet; Monozygotic twin pairs with differential habitual diet practices will undergo measurements including body composition, and MRI measures of hepatic adiposity and neuroinflammation.
Experimental: Study 2, A twin study of controlled diet; Monozygotic twin pairs will be provided an assigned diet for 14-days.	Behavioral: Diet modification; Participants will be provided all meals for a 14-day period. For 7 of the days, meals will be 150% of estimated daily caloric needs and for the other 7 days, meals will be low in calories, consistent with recommendations for weight loss.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Study 1: Hypothalamic Gliosis	T2 relaxation time as measured by brain MRI	at enrollment
Study 2: Hypothalamic Gliosis	T2 relaxation time as measured by brain MRI	7 days of diet intervention

Collaborators and Investigators

• Sponsor: University of Washington
• Collaborators: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
• Investigators: Principal Investigator: Ellen Schur, MD, MS, University of Washington

Study record dates

Study Major Dates

• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): November 1, 2029
• Study Completion (Estimated): April 30, 2030

Study Registration Dates

• First Submitted: February 18, 2026
• First Submitted That Met QC Criteria: February 18, 2026
• First Posted (Actual): February 24, 2026

Study Record Updates

• Last Update Posted (Actual): February 24, 2026
• Last Update Submitted That Met QC Criteria: February 18, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Gliosis; Eating patterns
• Additional Relevant MeSH Terms: Pathologic Processes; Nutrition Disorders; Overnutrition; Body Weight; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity; Gliosis; Therapeutics; Nutrition Therapy; Diet Therapy
• Other Study ID Numbers: STUDY00022649; R01DK144233 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No