Energy Expenditure Responses to Different Temperatures

May 29, 2026 updated by: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Background:

- The way that the body burns calories is known as energy expenditure. Some studies show that when we are cold, we burn more calories to keep our bodies warm. Brown fat is a special kind of fat that can use energy to keep the body warm. Small animals and infants have been known to have brown fat for many years. Recently, it has been suggested that adult humans also have brown fat. If brown fat becomes active (burns calories) in adult humans when exposed to cold, then these people would tend to burn off more calories and might not gain weight easily. Learning more about the relationship between energy expenditure, brown fat, environmental temperature, and body temperature may help explain why some people become obese and other people do not.

Objectives:

  • To better understand how the body burns calories when exposed to different temperatures.
  • To study brown fat and how it burns calories in cold temperatures.

Eligibility:

  • Healthy men between 18 and 35 or 55 and 75 years of age.
  • Healthy women between 18 and 35 years of age.
  • To control for ethnicity, participants must be non-Hispanic whites or African Americans.

Design:

  • Participants will be screened with a physical exam and medical history. Blood and urine samples will be collected.
  • Participants will stay in the Metabolic Unit of the National Institutes of Health Clinical Center as inpatients for no more than 14 days. The length of the hospital stay will depend on how participants respond to the different study temperatures.
  • Every afternoon, participants will walk for 30 minutes on a treadmill. All meals will be provided.
  • Participants will stay up to 5 hours per day in a specialized room with different temperature settings. Temperatures will range from about 61 degrees to 88 degrees Fahrenheit. Body temperature, activity, calorie burning, and cold/hot sensations will be monitored. On the study day of the coldest temperature, participants will have an imaging study to look for brown fat activity.
  • Participants will be compensated for their time and participation at the end of the study....

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Surprisingly little is understood about how the body regulates heat production (energy expenditure, EE) in response to subtle changes in environmental temperature. For example, only recently has it been realized that brown adipose tissue is functional in adult humans. It is plausible that the mechanisms governing heat production contribute to regulation of body weight and thus may be contributing to the current obesity epidemic: even small changes in EE, if not compensated by changes in food intake, can have long-term effects on body weight.

The thermoneutral zone (TNZ) is the environmental temperature range over which EE is at a minimum and does not change with environmental temperature. The lower and upper critical temperatures define the temperature limits of the TNZ. At environmental temperatures below the lower critical temperature, the EE vs. environmental temperature graph is reported to be a straight line with the extrapolated X-axis intercept being the defended body temperature. Some of these parameters are predicted to be different for obese as compared to lean individuals. With the global obesity epidemic coinciding with improved indoor temperature control, a better understanding of the relationship between EE and thermoregulation is desirable.

This protocol has three phases. The first is a pilot in lean males to optimize procedures and establish the feasibility, sensitivity, and behavior of the assays. Second, lean and obese male cohorts will be compared to ensure that the expected differences can be observed. Third, additional variables will be examined, such as age, race, sex, and menstrual phase in women.

Specifically, we will map the resting EE response to environmental temperatures from 16-31 degrees Celsius during inpatient stays in the NIH Metabolic Clinical Research Unit. Each day resting EE will be measured in a room respiration calorimeter with a different environmental temperature (subjects will be blinded as to room temperature). The remainder of each study day will be spent at 23-25 degrees Celsius in the individual patient room.

Standard diet and physical activity will be maintained and body weight will be held stable. Additionally core body and skin temperatures, heart rate and variability, muscle activity by surface electromyography, and thermal comfort and hunger using visual analog scales will be measured.

This study will establish techniques and provide baseline normative data, allowing insight into the mechanisms regulating the EE in humans and how these are affected by obesity. It is envisioned that this study will provide the basis for investigation of the effects of acute and chronic weight change and the effects of drug therapy.

Study Type

Interventional

Enrollment (Actual)

104

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Maryland
      • Bethesda, Maryland, United States, 20892
        • National Institutes of Health Clinical Center

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 75 years (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Description

  • INCLUSION CRITERIA:
  • Generally healthy.
  • Males between the age greater than or equal to 18 -35 years or between 55-75 years, male orand females between the age 18-35 years.
  • Self-reported non-Hispanic and non-Latino Caucasian and African-Americans
  • Written informed consent.

EXCLUSION CRITERIA:

  • Hypo- or hyper-thyroid (history or TSH >5.0<0.4 miU/L)
  • Psychological conditions,such as (but not limited to) claustrophobia, clinical depression, bipolar disorders, that would be incompatible with safe and successful participation in this study
  • Weight change >5% in the past 6 months or a trained athlete

Blood pressure greater than 140/90 mmHg or current antihypertensive therapy

  • History of cardiovascular disease
  • BMI <18.5, between 25.1-29.9, and >40 Kg/m(2)
  • Diabetes mellitus (fasting serum glucose > 126 mg/dL)
  • Liver disease or ALT serum level greater than two times the laboratory upper limit of normal
  • Iron deficiency (Ferritin < 30 mcg/L males, < 15 mcg/L females)
  • Abnormal kidney function (eGFR<60 ml/min/1.73m(2))
  • History of illicit drug or alcohol abuse within the last 5 years; current use of drugs (by history) or alcohol (CAGE greater than or equal to 2)
  • Current use of medications/dietary supplements/alternative therapies known to alter energy metabolism
  • Pregnancy/breastfeeding/hormonal contraception or childbirth within the last year
  • Perimenopausal (as self-described within two years from onset of amenorrhea or current complaints of hot flashes)
  • For pre-menopausal women, irregular periods or polycystic ovarian disease
  • Current smoker or user of tobacco products
  • Metal implant that prevents subject from being in a MRI scanner.

All subjects will be fully informed of the aims, nature, and risks of the study prior to giving written informed consent.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Non-Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Healthy older lean white men
White men aged 55-75 years with BMI between 18.5 and 25.0 kg/m2
Other: Room temperatures
Room temperature of metabolic chamber set between 16C and 31C
Experimental: Healthy young lean black men
Black men aged 18-35 years with BMI between 18.5 and 25.0 kg/m2
Other: Room temperatures
Room temperature of metabolic chamber set between 16C and 31C
Experimental: Healthy young lean white men
White men aged 18-35 years with BMI between 18.5 and 25.0 kg/m2
Other: Room temperatures
Room temperature of metabolic chamber set between 16C and 31C
Experimental: Healthy young lean white women
White women aged 18-35 years with BMI between 18.5 and 25.0 kg/m2
Other: Room temperatures
Room temperature of metabolic chamber set between 16C and 31C
Experimental: Healthy young white men with obesity
White men aged 18-35 years with BMI between 30.0 and 40.0 kg/m2
Other: Room temperatures
Room temperature of metabolic chamber set between 16C and 31C

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Resting energy expenditure
Time Frame: Days 7-13 of inpatient stay
Resting energy expenditure at the lowest tolerable temperature above basal metabolic rate (%), measured by metabolic chamber
Days 7-13 of inpatient stay

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Mean skin temperature
Time Frame: Days 1-14
Weighted average of skin temperatures measured by iBottons at the chest, upper arm, upper leg, and lower leg
Days 1-14

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Investigators

  • Principal Investigator: Kong Y Chen, Ph.D., National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

April 24, 2012

Primary Completion (Actual)

November 14, 2019

Study Completion (Actual)

November 14, 2019

Study Registration Dates

First Submitted

March 30, 2012

First Submitted That Met QC Criteria

March 30, 2012

First Posted (Estimated)

April 2, 2012

Study Record Updates

Last Update Posted (Actual)

June 1, 2026

Last Update Submitted That Met QC Criteria

May 29, 2026

Last Verified

October 14, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 120097
  • 12-DK-0097

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified IPD underlying the primary results

IPD Sharing Time Frame

From the time of publication and available indefinitely

IPD Sharing Access Criteria

Data will be shared with qualified investigators who provide a protocol with IRB approval. Data sharing requires a signed data use agreement.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • ICF

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Obesity

Clinical Trials on Room temperatures

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Argentina

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe