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EE: Room Conditions (2013)

Citation:

Claessens-van Ooijen AM, Westerterp KR, Wouters L, Schoffelen PF, van Steenhoven AA, van Marken Lichtenbelt WD. Heat production and body temperature during cooling and rewarming in overweight and lean men. Obesity (Silver Spring). 2006; 14(11): 1,914-1,920.

PubMed ID: 17135606
 
Study Design:
Non-Randomized Crossover Trial
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To investigate whether lean and overweight subjects differ in cold-induced thermogenesis under mild cold conditions. 

Inclusion Criteria:
  • Healthy subjects
  • Non-smoking
  • Male
  • Lean (BMI 17.9kg/m2 to 23.4kg/m2) or overweight (BMI 24.7kg/m2 to 33.2kg/m2)
  • Written consent was obtained.
Exclusion Criteria:
  • Females 
  • Smokers
  • BMI less than 17.9kg/m2 or >33.2kg/m2.
Description of Study Protocol:

Recruitment

Volunteers.

Design

Non-randomized crossover trial.

Blinding Used

Implied with measurements.

Intervention 

  • Cold air exposure test followed by rewarming
  • Thermoneutral condition was established:
    • Subjects lay on a chair, with legs supported in 15°C air and were covered with a duvet (375g per m2).
  • Cold exposure was started:
    • Duvet was removed after 60 minutes of baseline measurement.
  • Rewarming phase was started:
    • After 60 minutes of cold exposure, the duvet was replaced.
  • The test was terminated after 60 minutes of rewarming
  • Subjects wore standard clothing with insulative value of 0.71 clo (Icl = 0.109m2 x °C per W)
    • Sweatpants, sweater, socks that covered only the feet and briefs
    • Face, hands and ankles were exposed directly to the environment.
  • Heat production and body temperature were measured continuously 
  • Subjects arrived at the laboratory by car or public transportation after overnight fasting
  • Subjects instructed not to perform any strenuous activities the day before the experiment
  • Body composition was determined on a separate visit within one week of the experiment.

Statistical Analysis

  • Baseline values were calculated over minutes 21 to 50 of the first hour
  • During cold exposure and rewarming, minutes 11 to 60 were used for calculations
  • Data reported as means ± standard deviations
  • Results considered statistically significant at P<0.05
  • SPSS 11.5.0 was used
  • Between-group differences were tested by unpaired T-tests
  • Within-group changes were tested by paired T-tests
  • Linear regression analysis was used to study the relation between skin temperature and fat percentage. 
Data Collection Summary:

Timing of Measurements

  • Subjects exposed to thermoneutral condition for 60 minutes, followed by mild cold exposure for 60 minutes and then 60 minutes of rewarming
  • Body composition was determined on a separate visit within one week of the experiment  

Dependent Variables

  • Heat production
    • Oxygen consumption and carbon dioxide production were measured with an automated respiratory gas analyzer using a ventilated hood system (Omnical)
    • Gas analyzers were calibrated before the experiments
    • Heat production was calculated from these data according to Weir's method
  • Body Temperature
    • Rectal temperature was measured continuously by a thermistor probe inserted 10 cm beyond the anal sphincter
  • Skin temperature
    • Measured by surface thermistors placed on the dorsal side of the hand, forearm, upper arm, chest, abdomen, lower back, anterior thigh, posterior calf, and dorsal side of the foot
    • Temperatures were registered and recorded at 1-minute intervals
    • Mean skin temperature calculated according to Ramanathan's method
  • Weighted body temperature
    • Calculated as a measure of rectal and mean skin temperatures according to Cunningham
  • Trunk temperature
    • Calculated as the average of skin temperatures measured at the lower back, abdomen and chest
  • Distal skin temperature
    • Measured at the hand and foot
  • Shivering
    • Detected using electromyography
    • Electrodes were placed three cm apart on the skin at the musculus pectoralis major

Independent Variables

  • Thermoneutral condition
  • 15°C cold air exposure
  • Rewarming to thermoneutral condition

 Control Variables

  • Body composition
    • Calculated according to Siri's three-component model
    • Body density and total body water were determined using underwater weighing and deuterium dilution which was determined according to the Maastricht protocol

 

Description of Actual Data Sample:
  • Initial N: 10 lean and 10 overweight males
  • Attrition (final N): 10 lean and 10 overweight males.

Age

  • Lean: 23±4 years
  • Overweight: 27±7 years
  • Total group: 25±6 years.

Anthropometrics

  • Height (m):
    • Lean: 1.82±0.08
    • Overweight: 1.80±0.06.
  • Weight (kg):
    • Lean: 69.7±7.1
    • Overweight: 94.5±6.8.
  • BMI:
    • Lean: 21.1±2.0
    • Overweight: 29.2±2.8.
  • Fat mass (%):
    • Lean: 14.9±4.2
    • Overweight: 27.9±5.3.
  • Fat-free mass (kg)
    • Lean: 58.8±5.0
    • Overweight: 70.0±5.5.

Location

Maastricht, The Netherlands.

 

Summary of Results:

Key Findings

  • Cold exposure:
    • Heat production increased significantly for both groups compared to baseline:
      • Lean group: P=0.004
      • Overweight group: P=0.006
      • The increase was significantly larger in the lean group (17.2% average) compared to overweight (6.4% average) (P=0.04).
  • Weighted body temperature (WBT):
    • Decreased significantly during cold exposure (P=0.002 for lean and P<0.001 for overweight subjects)
    • During rewarming, WBT increased by did not return to baseline (P=0.01 for lean and P=0.003 for overweight groups) compared to baseline.

Other Findings

  • Subject characteristics: Weight, BMI, fat mass and fat-free mass were all significant between the lean and obese groups (P<0.05)
  • Baseline:
    • No significant differences between lean and overweight subjects in energy expenditure 
    • Only trunk temperature was lower in overweight men (P=0.02)
  • Cold exposure:
    • Heat production increased significantly for both groups compared to baseline:
      • Lean group: P=0.004
      • Overweight group: P= 0.006
      • The increase was significantly larger in the lean group (17.2% average) compared to overweight (6.4% average) (P=0.04).
  • Rewarming:
    • Heat production decreased in both groups:
      • Returned to baseline in the overweight group
      • Remained significantly higher compared with baseline in lean group (P=0.003)
      • Difference in heat production between rewarming and baseline was greater in the lean group compared to overweight group (P=0.01).
  • Temperatures:
    • Rectal temperature:
      • Not significantly different between groups at any stage of the experiment
      • Did not change significantly compared with baseline.
    • Trunk temperature:
      • Significantly lower in overweight group compared with lean group during the three stages (P=0.02, P=0.007 and P=0.006, respectively)
      • Within groups, trunk temperature decreased significantly during cold exposure (P<0.001) in both groups
      • During rewarming, trunk temperature was not significantly different from baseline in overweight group but stayed significantly lower compared with baseline in lean group (P=0.03).
    • Mean skin temperature:
      • Decreased significantly during cold exposure (P<0.001) in both groups
      • During rewarming, did not return to baseline in the two groups (P<0.001) compared to baseline.
    • Weighted body temperature (WBT):
      • Decreased significantly during cold exposure (P=0.002 for lean and P<0.001 for overweight subjects)
      • During rewarming, WBT increased by did not return to baseline (P=0.01 for lean and P=0.003 for overweight groups) compared to baseline.
    • Distal skin temperature:
      • Decreased significantly during cold exposure (P<0.001)
      • Increased during rewarming 
      • Did not return to baseline values in both groups (P<0.001 for both groups) compared to baseline.
    • Trunk temperatures:
      • Negatively related to fat percentage at baseline (R2=0.32, P=0.009)
      • Similar relationship during cold exposure (R2=0.40, P=0.003)
      • Similar relationship during rewarming (R2=0.36, P=0.005).
    • Distal skin temperature:
      • Positively related to fat percentage at baseline (R2=0.28, P=0.02)
      • During cold exposure (R2=0.25, P=0.03)
      • During rewarming (R2=0.29, P=0.01).

Heat Production and Body Temperatures at Baseline, During Cooling and Rewarming

Temperature and Group Baseline Cooling Rewarming
Heat production (W per m)   
Lean 44.7±3.1 53.4±7.2* 50.0±4.2*
Overweight 44.7±3.9 47.5±4.5* 45.9±4.7
Rectal temperature   
Lean 36.8±0.2 36.9±0.2 36.8±0.2
Overweight 36.9±0.2 36.9±0.2 36.9±0.2
Mean skin temperature   
Lean 32.4±0.4 29.6±0.8* 30.5±0.6*
Overweight 32.6±0.6 29.9±0.7* 30.6±0.7*
Trunk skin temperature   
Lean 34.6±0.2§ 32.7±0.4*§ 34.3±0.3*§
Overweight 33.9±0.8 32.0±0.6* 33.5±0.8
Distal skin temperature   
Lean 30.5±0.8 26.6±1.2* 27.0±1.1
Overweight 31.5±1.3 28.0±1.9* 28.2±1.9*
Weighted temperature   
Lean 36.8±0.2 36.5±0.2* 36.5±0.3*
Overweight 36.9±0.2 36.6±0.2* 36.6±0.3*

*P<0.05 vs. baseline.

§P<0.05 overweight vs. lean.

Author Conclusion:

This study demonstrated that overweight subjects showed a blunted cold-induced thermogenesis, but there was no difference in the insulative cold response between lean and overweight subjects. The results indicate that the overweight subjects preserved heat more efficiently through a smaller heat loss compared with body size.

Funding Source:
University/Hospital: Maastricht University and Technical University Eindhoven
Reviewer Comments:

Small numbers of subjects in groups. Questionable validity of indirect calorimeter.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? ???
2. Was the selection of study subjects/patients free from bias? ???
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  3. Were study groups comparable? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  4. Was method of handling withdrawals described? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  5. Was blinding used to prevent introduction of bias? Yes
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
  7. Were outcomes clearly defined and the measurements valid and reliable? ???
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
  9. Are conclusions supported by results with biases and limitations taken into consideration? No
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
  9.2. Are biases and study limitations identified and discussed? No
  10. Is bias due to study's funding or sponsorship unlikely? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes