EE: Thermic Effect of Food (2014)


Bissoli L, Armellini F, Zamboni M, Mandragona R, Ballarin A, Bosello O. Resting metabolic rate and thermogenic effect of food in vegetarian diets compared with Mediterranean diets. Ann Nutr Metab. 1999; 43: 140-144.

PubMed ID: 10545669
Study Design:
Non-Randomized Controlled Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  • To compare the RMR and thermogenic effect of food in a group of vegetarians compared to a group of subjects on a Mediterranean diet
  • To investigate if a vegetarian diet can influence energy metabolism and induce lower body weight.


Steady state: 20-minute, nonstop period when consecutive differences in measurements were less than 5%.

Inclusion Criteria:
  • Vegetarian group: Vegetarian for at least one year, verified by a three-day food diary and interview
  • Omniovores: University population in clinical nutrition department (physicians, dietitians, medical students following a Mediterranean diet rich in CHO and low in fats)
  • Healthy.
Exclusion Criteria:

Not meeting inclusion criteria for vegetarianism.

Description of Study Protocol:


  • Specific procedures for recruitment of vegetarian subjects were not specified
  • Non-vegetarians were recruited from the university population.


Non-randomized trial.

Statistical Analysis

  • Comparisons between the two groups were performed by ANOVA
  • Mean values for RQ, RMR and TEF were calculated adjusting for weight, age and gender by multiple regression.
Data Collection Summary:

Timing of Measurements

One measurement time.

Dependent Variables

  • Measured Resting Metabolic Rate (RMR) [(VO2 L per minute), VCO2 (L per minute; ml per kg per minute), RQ, ventilation (L per minute)]
    • IC type: MMC Horizon
    • Coefficient of variation using standard gases: No
    • Rest before measure (state length of time rested if available): Approximately 20
    • Measurement length: More than 25 minutes
    • Steady state: Yes
    • Fasting length: 12 hours
    • Exercise restrictions XX hour prior to test: Not specified
    • Room temp: Not specified
    • Numbers of measures within the measurement period: One
    • Were some measures eliminated? Yes, the amount to achieve steady state
    • Were a set of measurements averaged? Yes, the 15-minute period
    • Coefficient of variation in subjects measures? No
    • Training of measurer? Not specified
    • Subject training of measuring process? Yes
    • Monitored heart rate? No
    • Body temperature? No
    • Medications administered? No.
  • Measured Thermic Effect of Food (TEF):
    • After measurement of RMR, ventilated hood was removed and each subject consumed, in 10 minutes: Pasta (100g), with tomatoes and olive oil (5g) and bread (30g) providing 515kcal: 80% CHO (103g), 10% protein (13g) and 9% fat (5g)
    • Subject then returned to the ventilated hood and their post-prandial metabolic rate was measured every hour for 30 minutes for the next three hours
    • TEF calculated as the incremental area above RMR and is expressed as change kJ per minute and as percentage energy of RMR.

Independent Variables

  • Vegetarian diet vs. Mediterranean diet
  • Test meal.

Control Variables

  • Macronutrient intake (protein, CHO, lipids, fiber and alcohol)
  • Age
  • Gender
  • Weight: Measured
  • Height: Procedures not specified
  • BMIkg/m2.
Description of Actual Data Sample:
  • Final N: N=32:
    • Vegetarians: N=16 (six males, 10 females; five vegans, 11 lacto-ovo)
    • Non-vegetarians: N=16 (six males, 10 females).
  • Age:
    • Vegetarians: 34±9 years
    • Non-vegetarians: 30±5 years.
  • Ethnicity: Was not specified, but study was done in Italy.
  • Anthropometrics:
  Vegetarians Non-vegetarians
Height, cm 167±9.8 169±7.5
Weight, kg 60±11.3 63±11.5
BMI, kg/m2 21±2.1 22±2.5
  • Location: Italy.
Summary of Results:

Nutrient Intake

  Vegetarians (Mean±SD) Omnivores (Mean±SD)
kJ per day 7,727±3,516 8,970±2,273
kcal per day 1,847±840 2,144±543
Protein, % 10.1±1.7 13.4±2.5a
Protein, g per day 44.9±18.3 70.1±14.9a
Animal protein, g per day 13.2±13.1 40.2±12.9±a
Vegetable protein, g per daya 33.1±11.3 27.2±7.7
Carbohydrates, % 62.0±10.2 56.2±5.8
Lipids, % 28.6±9.7 28.4±5.4
Fiber, g per day 30.5±16.7 16.5±7.9b
Alcohol, g per day 0.5±1.5 8.9±12.2b

a P<0.001; b P<0.05.

  • The percent of protein intake was significantly higher in omnivorous subjects while fiber per day was significantly higher in the vegetarian group
  • The percent of energy from CHO was almost significantly higher in vegetarians than omnivores.

Indirect Calorimetry Results

  Vegetarians (Mean±SD) Omnivores (Mean±SD)
RQ 0.84±0.09 0.88±0.13
RMR, kJ per minute 4.23±0.96 4.06±0.54
RMR, kcal per minute 1.01±0.23 0.97±0.13
TEF, kJ per minute 0.50±0.25 0.38±0.25
TEF, kcal per minute 0.12±0.06 0.09±0.06
TEF, % energy 12.0±7.2 10±6.8
RQb 0.85±0.1 0.88±0.1
RMR, kJ per minuteb 4.27±0.63 4.02±0.38
RMR, kcal per minuteb 0.12±0.07 0.09±0.06b
TEF, kJ per minuteb 44.9±18.3 70.1±4.9a
TEF, kcal per minuteb 13.2±13.1 40.2±12.9a
TEF, % energyb 33.1±11.3 27.2±7.7


b After adjustment for weight, age and gender.

  • No significant differences between groups were observed in RQ, RMR and thermic effect of food
  • No significant differences were observed in RQs after the meals at the first, second and third hour
  • Results did not change after correcting for weight, age and gender.
Author Conclusion:
  • Our study failed to show any significant differences in calorimetric measures between vegetarian subjects and omnivorous subjects on a Mediterranean diet. All that was observed was a non-significant lower RQ, higher RMR and TEF in vegetarians.
  • Previous findings suggest differences. Poehlman found a lower TEF in vegetarians; Oberlin et al did not find significant differences in RMR in young vegetarian and non-vegetarian women and Toth and Poehlman showed that RMR in vegetarians was 11% higher than non-vegetarians. The difference disappeared when the high-carbohydrate, low-fat diet and high-plasma noradrenaline levels of vegetarians were taken into account.
  • One limitation of our study is the diet of omnivorous subjects was very similar to that of vegetarians, differing only for higher protein and lower fiber content; CHO content was not significantly different
  • Vegetarianism per se is not accompanied by a difference in RMR and TEF when the carbohydrate content of the diet is similar to a control group of non-vegetarians.
Funding Source:
Government: Servizio Clinicizzato di Geriatria
Reviewer Comments:


Used appropriate tools to measure diet intake and measure RMR.


  • Generalizability to healthy, non-obese adults, both vegetarian and those who adhere to a healthy diet that includes meat
  • Study biases include sampling methods since the subjects in the Mediterranean diet (i.e., omnivores) were educated in nutrition and healthy eating (e.g., 16.5g fiber per day, 28.4% kcal from fat) and do not represent a typical adult in U.S. (e.g., percent of calories of fat are higher than 30 and 0g to 5g a day)
  • Both groups became more aware of eating patterns because they had to keep a three-day food diary
  • An intervening variable was not measured fat-free mass not measured and thus not analyzed as a covariate; there is no description of how height was measured (if it was) and measuring weight technique (i.e., with light clothing or standard clothing; with or without shoes)
  • Important variables on REE measurement accuracy: Possible exercise the day before measure.
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? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? No
  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? ???
  2.2. Were criteria applied equally to all study groups? 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? ???
3. Were study groups comparable? No
  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? ???
  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
  3.5. 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? No
  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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  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? 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
  7.4. 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? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  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
  8.1. 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
  8.3. 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
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? ???
  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
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes