EE: Thermic Effect of Food (2014)


Poehlman ET, Arciero PJ, Melby CL, Badylak SF. Resting metabolic rate and postprandial thermogenesis in vegetarians and nonvegetarians. Am J Clin Nutr. 1988; 48: 209-213.

Study Design:
Non-Randomized Crossover Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  • To investigate RMR, TEM and hormonal changes in vegetarians and nonvegetarians of comparable aerobic fitness and body fat content
  • Hypothesis: Chronic adaptation to a low-fat, high-complex CHO vegetarian diet could alter RMR and TEM, which promote lower body weight and body fat.


  • Total TEM: The kcal expended during 180 minutes following consumption of liquid meal minus the basal RMR during the 180 minutes and then multiplying by 180 minutes
  • Percentage TEM: kcal intake per total TEM kcal per 180 minutes.
[Analyst note: This is verbatim definition from article; however, when checking using reported numbers to insert, the result does not match the reported percentage TEM; Hence, reported percentage TEM as given in Table 3.]
Inclusion Criteria:
  • Understand and give written consent
  • Healthy
  • For vegetarian, practicing for at least one year
  • For non-vegetarian, eats meat on a daily basis
  • Weight stable within the past six months.
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria.
Description of Study Protocol:


  • Height measured? Yes
  • Weight measured? Yes
  • Fat-free mass measured? Yes, underwater weighing.


  • Monitored heart rate? Yes
  • Body temperature? No
  • Medications administered? No
  • Monitored blood pressure? Yes.

Resting Energy Expenditure

  • IC type: Sensormedics, ventilated hood
  • Equipment of Calibration: Yes
  • Coefficient of variation using std gases: No
  • Rest before measure (state length of time rested if available): 30 minutes
  • Measurement length: 30 minutes
  • Measurement duration: 180 minutes
  • Steady state: Used a 30-minutes acclimation period
  • Fasting length: 12 hours
  • Exercise restrictions XX hr prior to test? Not specified
  • Room temp: 24°C
  • Number of measures within the measurement period: Baseline, and continuous for 180 minutes after consuming Sustacal
  • Were some measures eliminated? No
  • Were a set of measurements averaged? No, continuous measure
  • Coefficient of variation in subjects’ measures? No
  • Training of measurer? Likely
  • Subject training of measuring process? Yes.


  • Consumed Sustacal, 10kcal per kg fat-free weight; 24% protein, 55% CHO, 21% fat
  • The results:
    • Vegetarians: 621.7±19.9kcal
    • Non-vegetarian: 677.2±19.2kcal
  • Measured via three-day food record.
Data Collection Summary:

Outcome(s) and Other Measures

  • Measured REE [(VO2, L per minute), VCO2 (L per minute; ml per kg per minute), RER, ventilation (L per minute)]
  • Independent variables of weight, height, age, BMI, fat-free mass, percent body fat
  • Plasma triiodothyronine (T3) and thyroxine (T4), blood pressure, plasma glucose.
Description of Actual Data Sample:
  • Younger aged males:
    • N=23 young males aged 18 to 37 years
    • Mean age: 24.8 years.
  • Vegetarian, N=12: Mean age, y(±SEM): 27.0±1.9.*
  • Non-vegetarian, N=11
    • Mean age, y(±SEM): 22.5±0.9
    • *P<0.05.
  • Statistical tests:
    • One-way ANOVA for differences between mean scores
    • Two-way repeated measures ANOVA
    • Pearson product correlations to test associations
    • Mean±SEM.
Summary of Results:


Men Vegetarian (Mean±SEM) Non-Vegetarian (Mean±SEM)
Weight, kg 71.2±1.8 78.8±2.6*
Height, cm 180.0±0.006 180±0.020
BMI, kg/m2 22.7±0.4 24.4±0.8
Fat-free body mass 62.1±2.0 67.7±1.9
Body fat, percent 12.8±1.3 13.8±16.0


Non-vegetarians were slightly younger and heavier than vegetarians.

Measurement Process

  • Number of measurement intervals: Two baseline and continuous 180 minute measure
  • Length of measurements: 30, 180 minutes.

Dietary Results

Men Vegetarian (Mean±SEM) Non-Vegetarian (Mean±SEM)
Energy intake, kcal per day 3,229±202* 2,807±371
Protein (percent) 13.0±1.1* 15.8±0.8
CHO (percent) 61.1±3.6* 45.0±3.0
Fat (percent) 26.0±2.8* 39.2±3.2

*P<0.05 difference between groups (vegetarians vs. non-vegetarians).

A large variation in daily energy intake was noted in non-vegetarians.

RMR Results

There were no significant differences (P>0.05) between the two groups in absolute RMR (kcal per minutes) and in RMR expressed per kg body weight and per kg FFW.

Men Vegetarian (Mean±SEM) Non-Vegetarian (Mean±SEM)
RMR, kcal per minute 1.14±0.04* 1.18±0.04


Thermic Effect of the Meal Test

The average change in TEM was significantly lower (P=0.01) in vegetarians (0.31kcal±0.02kcal per minute) than in non-vegetarians (0.42±0.02).

Change in TEM (kcal Per Minute)

Postprandial Time, Minute Net Change kcal Per Minute (Vegetarians) Net Change kcal Per Minute (Non-Vegetarians)
0 N/A N/A
30 0.25 0.33
60 0.31 0.45
90 0.31 0.43
120 0.30 0.48
150 0.30 0.44
180 0.30 0.39
  • Estimates taken from Figure 1 that are changes in thermic effect of a meal (TEM)
  • Total TEM (kcal per 180 minutes) was 55.8±3.3 in vegetarians and 76.42±3.6 in non-vegetarians.

TEM as Percent of Caloric Content of Meal

  • Percent TEM was 9.09±0.6 and 11.37±0.6 in vegetarians and non-vegetarians, respectively
  • Total thermic effect of a meal was lower in vegetarians than non-vegetarians when expressed as TEM, when standardized for body weight and FFW
  • Total thermic effect of a meal was lower in vegetarians than non-vegetarians when expressed as TEM, when expressed as a percentage increase relative to the caloric load (%TEM).
Author Conclusion:

As stated by the author in body of report:

  • The present study showed a non-significant lower absolute RMR in vegetarians than in non-vegetarians whereas when RMR was adjusted fro body weight and FFW, a tendency toward a higher RMR in vegetarians was noted
  • This study showed a 25% lower TEM in vegetarians than in non-vegetarians. The difference persisted when standardized for body weight and FFW..... our results support an alteration in postprandial metabolic efficiency and may result from a presently unexplained adaptive response to a vegetarian diet
  • One could argue whether thermic response was genuinely reduced or artificially blunted because total TEM was not measured; however, differences in postprandial response were large and it is unlikely that prolonged measurements would have attenuated these differences
  • The significant positive relationship noted between plasma T3 and habitual energy intake suggests that the level of caloric intake may be an important regulator of this hormone. The lower energy intake in vegetarians than in non-vegetarians may be a contributing factor to the lower plasma T3 level and postprandial thermogenic response.
  • Lowered efficiency of postprandial energy utilization does not contribute to a lower body weight in vegetarians than in omnivores and vegetarians showed a similar RMR to and a lower TEM than that for non-vegetarians.
Funding Source:
University/Hospital: University of Vermont, Purdure University
Reviewer Comments:


  • Research plan controlled for differences in adiposity and FFW as well as recruiting various levels of physical activity
  • RMR measured continuously using a standardized protocol
  • Appropriate statistics.


  • Convenience sampling bias; does not report middle- and older-aged adults
  • Ethnicity of subjects was not reported
  • These are important variables on REE measurement accuracy; did not report steady-state monitoring over the 180 minutes (i.e., three hours).
  • Non-vegetarians had a higher fat dietary intake and weakens theory thermic effect of a test meal was measured within 180 minutes.
  • Included one to four individuals within varying vegetarian practice with regards to protein intake. Such small samples may limit generalizability to a broad range of practicing vegetarians.
  • Test meal was liquid whereas routine dietary intake differences in fiber were significant; this may also be an intervening variable.

NOTE: This paper did not receive government funding. The data falsification took place much later, and this paper was not mentioned in any of the claims against Poehlman, so this paper was accepted.

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) 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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? N/A
2. Was the selection of study subjects/patients free from bias? 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? N/A
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
3. Were study groups comparable? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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
  3.6. 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? No
  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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? 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
5. Was blinding used to prevent introduction of bias? No
  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.) 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
  5.5. 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
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? 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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? No
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
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? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? 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
  8.6. Was clinical significance as well as statistical significance reported? 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
  9.1. Is there a discussion of findings? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A