Postprandial Nutrient Homeostasis Before and After Weight Loss Induced by Low-calorie Diet or RYGB (FGB)

The purpose of this study is to compare the metabolic responses to low-carbohydrate and standard-carbohydrate meals in African Americans and non-Hispanic White adults with obesity and the effect of weight loss induced by low-calorie diet (LCD) or Roux-en-Y gastric bypass (RYGB) on the metabolic responses to low-carbohydrate and standard meals. Participants will consume: 1) a standard-carbohydrate meal (~49 g glucose) and 2) a low-carbohydrate (~3.4 g glucose) meal on separate study visits performed in a randomized order. We will evaluate the meals' effect before and after ~16-18% weight loss on postprandial i) insulin kinetics, ii) glucose kinetics iii) β-cell function; iv) plasma triglyceride and non-esterified fatty acid concentrations; v) plasma hormone concentrations; vi) plasma cytokine concentrations; vi) plasma metabolomics; and vii) adipose tissue transcriptomics.

Study Overview

• Status: Active, not recruiting
• Conditions: Obesity
• Intervention / Treatment: Procedure: Roux-en-Y gastric bypass surgery; Behavioral: Low-calorie diet

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Missouri
    • St Louis, Missouri, United States, 63110
      • Beth Henk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 25 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

Surgery Group (RYGB):

• Males and Females
• Scheduled for RYGB surgery
• Body Mass Index 35-60 kg/m²
• Without Type 2 Diabetes (T2D)

LCD group:

• Males and Females
• Body Mass Index 35-60 kg/m²
• Without Type 2 Diabetes (T2D)

Exclusion Criteria:

• Regular use of tobacco products
• Previous intestinal resection
• Pregnant or breastfeeding
• Evidence of significant organ system dysfunction or disease other than obesity and T2D
• Use of any medication that might, in the opinion of the investigator, affect metabolic function
• Exercise ≥90 minutes per week
• Use or past use of hormone replacement therapy within the past 6 months

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: RYGB group; Subjects in this group are scheduled to undergo Roux-en-Y gastric bypass surgery and will be assessed after ~16-18% weight-loss	Procedure: Roux-en-Y gastric bypass surgery; Roux-en-Y gastric bypass surgery will be performed with post-weight loss testing performed after ~16-18% weight loss is achieved.
Active Comparator: LCD Group; Subjects in this group will participate in a low-calorie diet intervention to achieve ~16-18% weight loss.	Behavioral: Low-calorie diet; Subjects will meet with a dietitian and/or behaviorist over 4-6 months to lose ~16-18% of their body weight.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Postprandial plasma insulin kinetics	Plasma insulin kinetics will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Postprandial plasma insulin kinetics	Plasma insulin kinetics will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Postprandial glucose kinetics	Plasma glucose kinetics will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Postprandial glucose kinetics	Plasma glucose kinetics will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)
β-cell function	β-cell function will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
β-cell function	β-cell function will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)
Postprandial triglyceride concentrations	Plasma triglyceride concentrations will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Postprandial triglyceride concentrations	Plasma triglyceride concentrations will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)
Postprandial non-esterified fatty acid concentrations	Plasma non-esterified fatty acid concentrations will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Postprandial non-esterified fatty acid concentrations	Plasma non-esterified fatty acid concentrations will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)
Postprandial hormone concentrations	Plasma hormone concentrations will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Postprandial hormone concentrations	Plasma hormone concentrations will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)
Postprandial cytokine concentrations	Plasma cytokine concentrations will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Postprandial cytokine concentrations	Plasma cytokine concentrations will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)
Postprandial lipids	Plasma lipids will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal by using mass spectrometry.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Postprandial lipids	Plasma lipids will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal by using mass spectrometry.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)
Postprandial metabolites	Plasma metabolites will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal by using mass spectrometry.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Postprandial metabolites	Plasma metabolites will be assessed in blood samples collected before and after consuming a standard-carbohydrate or a low-carbohydrate meal by using mass spectrometry.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)
Transcriptome in adipose tissue	The transcriptome (all RNA that are responsible for making proteins from DNA templates) will be evaluated by using RNA sequencing techniques in adipose tissue samples collected before and ~3h after consuming a standard-carbohydrate or a low-carbohydrate meal.	Baseline only (cross-sectional comparison of metabolic responses in African American and non-Hispanic White adults with obesity)
Transcriptome in adipose tissue	The transcriptome (all RNA that are responsible for making proteins from DNA templates) will be evaluated by using RNA sequencing techniques in adipose tissue samples collected before and ~3h after consuming a standard-carbohydrate or a low-carbohydrate meal.	After 16-18% weight loss induced by LCD or RYGB (~4-6 months)

Collaborators and Investigators

• Sponsor: Washington University School of Medicine
• Collaborators: Kilo Diabetes & Vascular Research Foundation
• Investigators: Principal Investigator: Samuel Klein, MD, Washington University School of Medicine

Publications and helpful links

General Publications

• Li E, Wang L, Wang D, Chi J, Lin Z, Smith GI, Klein S, Cohen P, Rosen ED. Control of lipolysis by a population of oxytocinergic sympathetic neurons. Nature. 2024 Jan;625(7993):175-180. doi: 10.1038/s41586-023-06830-x. Epub 2023 Dec 13.

Study record dates

Study Major Dates

• Study Start (Actual): April 25, 2017
• Primary Completion (Actual): July 3, 2025
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: March 13, 2017
• First Submitted That Met QC Criteria: March 21, 2017
• First Posted (Actual): March 27, 2017

Study Record Updates

• Last Update Posted (Actual): August 25, 2026
• Last Update Submitted That Met QC Criteria: August 21, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: Obesity; Roux-en-Y gastric bypass (RYGB); Low calorie diet
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity; Therapeutics; Diet, Food, and Nutrition; Physiological Phenomena; Nutritional Physiological Phenomena; Diet Therapy; Nutrition Therapy; Diet; Energy Intake; Caloric Restriction
• Other Study ID Numbers: 201612107; UL1TR000448 (U.S. NIH Grant/Contract); KL2TR000450 (U.S. NIH Grant/Contract)

Drug and device information, study documents

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