Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  1. To compare the RMR and thermogenic effect of food in a group of vegetarians compared to a group of subjects on a Mediterranean diet.
  2. To investigate if a vegetarian diet can influence energy metabolism and induce lower body weight.


  • Steady state: 20 min, nonstop period when consecutive differences in measurements were <5%.
Inclusion Criteria:
  1. Understand and give written consent
  2. For vegetarian group: vegetarian for at least 1 year; For omnivores university population in clinical nutrition department (physicians, dietitians, medical students following a Mediterranean diet rich in CHO and low in fats:
  3. Healthy.
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria for vegetarianism
  3. Unhealthy.
Description of Study Protocol:


  • Ht measured? Yes
  • Wt measured? Yes
  • Fat-free mass measured? No


  • Monitored heart rate? No
  • Body temperature? No
  • Medications administered? No

Resting energy expenditure

  • IC type: MMC Horizon
  • Equipment of Calibration:
  • Coefficient of variation using std gases: No
  • Rest before measure (state length of time rested if available): ~20
  • Measurement length: >35 min
  • Measurement duration: 3 hr
  • Steady state: Yes
  • Fasting length: 12 hr
  • Exercise restrictions XX hr prior to test? Not specified
  • Room temp: Not specified
  • No. of measures within the measurement period: 1
  • Were some measures eliminated? Yes, amount to achieve steady state
  • Were a set of measurements averaged? Yes, the 15 min period
  • IF avg., identify length of each measure & no. of measurements?
  • Coefficient of variation in subjects’ measures? No
  • Training of measurer? NS
  • Subject training of measuring process? Yes


  • 3-day food diaries were completed to verify vegetarian status; Dietary records were analyzed for total energy and nutrient content;
  • The meal had to be eaten in 10 mins: 100 g pasta w/tomatoes and olive oil (5 g); 30 grams of bread=515 kcal: 80% CHO; 10% prot; 9% fat.
Data Collection Summary:

Outcome(s) and other measures

  1. Measured REE [(VO2, l/min), VCO2 (l/min; ml/kg/min), RQ, ventilation (l/min)].
  2. Macronutrient intake (protein, CHO, lipids, fiber and alcohol)
  3. Independent variables of weight, height, age, BMI, and fat-free mass, fat mass

Blinding used: No

Description of Actual Data Sample:
  • N=32 (12M;20F)

Vegetarians, n=16 (6M;10F)

  • (N=5 vegans; 11 lacto-ovo vegetarians)
  • Mean age: 34±9 y
  • BMI 21±2

Omnivores (Mediterranean diet), n=16 (6M;10F)

  • Mean age: 30±5 y
  • BMI 22±3

Statistical tests

Comparisons between 2 groups by ANOVA; Man values for RQ, RMR and TEF, adjusting for weight, age and gender by multiple regression

Summary of Results:




kJ/day 7727±3516 8970±2273


1847±840 2144±543

Protein, %

10.1±1.7 13.4±2.5a

Protein, g/day

44.9±18.3 70.1±14.9 a

Animal protein, g/day

13.2±13.1 40.2±12.9 a

Vegetable protein, g/day a



Carbohydrates, %



Lipids, %



Fiber, g/d


16.5±7.9 b

Alcohol, g/day


8.9±12.2 b

a P<0.001; b P<0.05

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



Vegetarians Mean±SD

RQ 0.84±0.09 0.88±0.13

RMR, kJ/min



RMR, kcal/min



TEF, ?kJ/min



TEF, ?kcal/min



TEF, % energy

12.0±7.2 10±6.8
RQ b 0.85±0.1 0.88±0.1

RMR, kJ/min b

4.27±0.63  4.02±0.38

RMR, kcal/min b



TEF, ?kJ/min b



TEF, ?kcal/min b



TEF, % energy b



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 1st, 2nd and 3rd 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 nonsignificant 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 nonvegetarians. 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.
Funding Source:
Reviewer Comments:
  • Strengths

“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., 16.5 grams of fiber/d, 28.4% kcal from fat) and do not represent a “typical” adult in U.S. (e.g., % calories of fat >30 and 0-5 grams fiber/day)/.
  • Both groups became more aware of eating patterns since had to keep 3-day food diary
  • An intervening variable 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 (with light clothing or standard clothing; with or without shoes?);
  • These are important variables on REE measurement accuracy: possible exercise the day before measure, machine calibration
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? 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? 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? Yes
  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? Yes
  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