Evaluating Metabolic Health in Individuals With Extreme Obesity

NCT07613255 | Not Yet Recruiting

• 1 other identifier: PBRC 2026-011
• Study Type: observational
• Target: 10
• Locations: 0 countries
• Sites: N/A

Brief Summary

This research will evaluate energy metabolism (expenditure and fat oxidation), metabolic flexibility (response to a high-fat test meal) in 10 individuals with a BMI ≥60 kgm2 using gold-standard assessments of energy metabolism, metabolic flexibility, and body composition. Males and females (18-80 y) with extreme obesity (BMI: ≥60 kg/m2) will be recruited from Baton Rouge, Louisiana. Exclusion criteria include major organ failure, uncontrolled endocrine disease, severe psychiatric illness, pregnancy, and inability to comply with study procedures. The total duration of participation for each individual is estimated at approximately 10 days. If qualified, participants (BMI≥60 kg/m2; n=10) will complete one outpatient visit and one inpatient visit with 36hr metabolic chamber testing.

Conditions

BMI>40

Keywords

metabolic flexibility; metabolism; extreme obesity; body composition

Outcome Measures

Primary Outcomes (8)

• 24-hour Energy Expenditure

  24-hour energy expenditure will be assessed from participants spending 23 hours in a metabolic chamber.

  Day 9

• 24-hour Fat Oxidation

  This will be collected from the 23-hour chamber stay during Visit 2, Day 2. Specifically, this represents the total grams of fat oxidized over the 23-hour stay, calculated from indirect calorimetry stoichiometry.

  Day 9

• Basal Energy Expenditure

  This represents the amount of energy expended under strict basal conditions: post-absorptive (typically 10-12h fasted), thermoneutral, fully awake but supine and motionless, no recent physical activity. This will be collected from the 23-hour metabolic chamber stay.

  Day 9

• Resting Energy Expenditure

  This is the energy expended at rest but under less stringent conditions than basal: seated or supine, awake, post-absorptive but with less rigor about prior activity, temperature, and emotional state. This will be collected from the 23-hour metabolic chamber stay.

  Day 9

• Sleeping Metabolic Rate

  This is the energy expenditure during sleep, typically computed from the lowest stable \~3-hour window between roughly 02:00 and 05:00 when arousal and movement are minimal. Per our Standard Operating Procedures, this will be computed between 01:00 and 05:00.

  Day 9

• Thermic Effect of Food

  This represents the postprandial rise in energy expenditure above the pre-meal baseline, integrated over the period until energy expenditure returns to baseline (typically 4-6 hours for a mixed meal). This reflects the energy cost of digestion, absorption, and substrate processing, plus a sympathetic activation component.

  Day 9

• Spontaneous Physical Activity

  This is the energy expended on non-volitional movement: fidgeting, postural adjustments, small spontaneous movements during otherwise sedentary periods in the chamber. It is commonly measured by radar/Doppler motion sensors and quantified either as a fraction of chamber time active (% activity) or as the energy cost of activity above sleeping metabolic rate.

  Day 9

• Free-living Total Daily Energy Expenditure

  This is the gold-standard free-living EE measurement: participants drink a dose of ²H₂¹⁸O, and the differential elimination rates of the two isotopes over \~7-14 days yield CO₂ production and therefore EE under habitual living conditions. It captures everything the chamber misses: occupational and recreational activity, environmental temperature variation, real meal patterns.

  Day 1 to Day 8

Secondary Outcomes (5)

• Time to Food Quotient

  Day 8

• Respiratory Exchange Ratio: Food Quotient Ratio

  Day 8

• ΔRespiratory Exchange Ratio Nadir

  Day 8

• Post-meal Respiratory Exchange Ratio Slope

  Day 8

• Time to Respiratory Exchange Ratio Nadir

  Day 8

Other Outcomes (6)

• Skeletal Muscle Mass

  Day 1 to Day 5

• Fat-free Mass

  Day 1

• Fat Mass

  Day 1

Study Arms (1)

Metabolic Flexibility

Ten Males and females (18-80 y) with extreme obesity (BMI: ≥60 kg/m2) will complete one outpatient visit and one inpatient visit with 36 hours of metabolic chamber testing evaluate energy metabolism (expenditure and fat oxidation), metabolic flexibility (response to a high-fat test meal) using gold-standard assessments of energy metabolism, metabolic flexibility, and body composition.

Other: High-fat test meal

Interventions

High-fat test meal OTHER

At Visit 2-D1, subjects will enter the chamber at approximately 17:30 and exit the following morning at 07:00. Energy expenditure, respiratory exchange ratio (RER), and 12-h oxidation of CHO, fat, and protein will be calculated per standard PBRC protocols. While in the chamber, participants will collect all their urine for measurement of urinary nitrogen. Subjects will be served one high-fat meal while they are in the chamber (40% of the daily energy requirements).

Also known as: metabolic flexibility

Metabolic Flexibility

Eligibility Criteria

• Age: 18 Years - 80 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

The population for this study is individuals aged 18 to 80 years old who have a BMI greater than or equal to 60 kg/m2 who are willing to consume pre-prepared meals and are willing to have biospecimens and images stored for future use. The reason for seeking to evaluate this specific population is because individuals with extreme obesity possess high surgical and comorbidity risks, but there is a very small amount of research conducted in these individuals.

You may qualify if:

• Healthy male or female
• Between 18 - 80 years of age
• BMI ≥60 kg/m2
• Willing to consume pre-prepared meals
• Willing to comply with the study procedures.
• Willing to have biospecimens and images stored for future use.

You may not qualify if:

• Diabetic individuals with complications such as:
• Diabetic eye disease requiring laser treatment
• Diabetic nerve disease associated with foot ulcers or amputations
• Diabetic vascular disease associated with gangrene or amputation
• Diabetic kidney disease accompanied by a creatinine greater than 2.0 mg/dL
• Individuals with prior gastrointestinal surgery except appendectomy or cholecystectomy
• Individuals with untreated thyroid disease
• Individuals with untreated or poorly controlled binge eating disorder, bulimia, substance abuse or dependence, mania, and psychosis.
• Women who are pregnant, trying to become pregnant, or currently breastfeeding.
• Individuals with major organ system failure like cirrhosis, hepatic insufficiency, portal hypertension, severe renal insufficiency or on dialysis, severe arterial insufficiency, dementia or the inability to give an informed consent.
• Being unwilling to comply with the study procedures.
• Not willing to have biospecimens and/or images stored for future research use.

Sponsors & Collaborators

• Pennington Biomedical Research Center: lead

Related Publications (6)

• Racette SB, Schoeller DA, Luke AH, Shay K, Hnilicka J, Kushner RF. Relative dilution spaces of 2H- and 18O-labeled water in humans. Am J Physiol. 1994 Oct;267(4 Pt 1):E585-90. doi: 10.1152/ajpendo.1994.267.4.E585.

  PMID: 7943308 BACKGROUND

• Schoeller DA. Measurement of energy expenditure in free-living humans by using doubly labeled water. J Nutr. 1988 Nov;118(11):1278-89. doi: 10.1093/jn/118.11.1278.

  PMID: 3142975 BACKGROUND

• McDougal DH, Sanchez-Delgado G, Flanagan EW, Marlatt KL, Sparks JR, Yang S, Redman LM, Ravussin E. Validation of a novel approach to assess metabolic flexibility to a high-fat meal in a whole-body room calorimeter. Obesity (Silver Spring). 2025 Apr;33(4):743-753. doi: 10.1002/oby.24245. Epub 2025 Mar 6.

  PMID: 40051190 BACKGROUND

• McDougal DH, Marlatt KL, Beyl RA, Redman LM, Ravussin E. A Novel Approach to Assess Metabolic Flexibility Overnight in a Whole-Body Room Calorimeter. Obesity (Silver Spring). 2020 Nov;28(11):2073-2077. doi: 10.1002/oby.22982. Epub 2020 Sep 27.

  PMID: 32985108 BACKGROUND

• Galgani JE, Fernandez-Verdejo R. Pathophysiological role of metabolic flexibility on metabolic health. Obes Rev. 2021 Feb;22(2):e13131. doi: 10.1111/obr.13131. Epub 2020 Aug 19.

  PMID: 32815226 BACKGROUND

• Kachmar M, Albaugh VL, Yang S, Corpodean F, Heymsfield SB, Katzmarzyk PT, Freedman DS, Schauer PR. Disproportionate increase in BMI of >/=60 kg/m2 in the USA. Lancet Diabetes Endocrinol. 2025 Jun;13(6):463-465. doi: 10.1016/S2213-8587(25)00069-5. Epub 2025 Apr 24. No abstract available.

  PMID: 40288378 BACKGROUND

Biospecimen

Retention: SAMPLES WITH DNA

A fasting blood sample will be collected at the Screening Visit to assess overall health (Chem26 including lipid panel and CBC). Blood samples will also be collected at Visits 1, 2-D1, and 2-D2 to assess metabolic, inflammatory, and aging biomarkers. Serum and plasma archives will be collected as follows: 1. Outpatient at Visit 1 a. Fasting blood sample at baseline (3 ml) and again at 4 hours (3 ml) for sodium bromide dilution. 2. Outpatient at Visit 1, Inpatient at Visits 2-D1 and 2-D2. a. 10ml plasma and 10ml serum 3. Outpatient at Visit 1, Inpatient at Visits 2-D1 and 2-D2 a. Blood samples (5 ml serum, 4ml purple top with a protease inhibitor cocktail) will be collected in the fasting state for glucose, insulin, C-peptide, ghrelin, and leptin.

MeSH Terms

Conditions

Obesity, Morbid

Condition Hierarchy (Ancestors)

Obesity; Overweight; Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Study Officials

• Christian Rodriguez, PhD

  Pennington Biomedical Research Center

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Christian Rodriguez, PhD

CONTACT

8062249114; christian.rodriguez@pbrc.edu

Eric Ravussin, PhD

CONTACT

2257633186; eric.ravussin@pbrc.edu

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: CROSS SECTIONAL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: T32 NIH Postdoctoral Fellow, Clinical Sciences, Principal Investigator

Study Record Dates

• First Submitted: May 13, 2026
• First Posted: May 29, 2026
• Study Start (Estimated): July 1, 2026
• Primary Completion (Estimated): July 1, 2026
• Study Completion (Estimated): August 1, 2026
• Last Updated: May 29, 2026

Record last verified: 2026-05