EE: Caffeine and Other Stimulants (2014)


Komatsu T, Nakamori M, Komatsu K, Hosoda K, Okamura M, Toyama K, Ishikura Y, Sakai T, Kunii D, Yamamoto S. Oolong tea increases energy metabolism in Japanese females. J Med Invest. 2003; 50(3-4): 170-175.

PubMed ID: 13678386
Study Design:
Randomized Crossover Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To determine whether or not the consumption of oolong tea increases energy expenditure in comparison with green tea.

Inclusion Criteria:
  • Provided written informed consent
  • Healthy, young women from a student population in Japan
  • Provided a medical and nutritional history via questionnaire.
Exclusion Criteria:
  • Smokers
  • Those who engaged in intense physical activity
  • History of weight loss.
Description of Study Protocol:


Healthy young women were recruited from the student population majoring in nutrition at a university.


Randomized crossover trial.

Blinding Used

Implied with measurements.


  • The treatments were water, oolong tea and green tea, with consumption of the test beverage for 120 minutes
  • In comparison with green tea, oolong tea contains approximately half the caffeine and epigallocatechin galate, and it has double the polymerized polyphenols.

Statistical Analysis

  • All values are expressed as means ±SE and analyzed using a procedure from SAS/ATAT software, version 8 of the SAS system for personal computers
  • Statistical comparisons were made by ANOVA
  • Significant differences in energy expenditure and RQ among treatments were determined by the Tukey-Kramer test and repeated measurements in each treatment were determined using the paired T-test with the comparison to the REE level
  • Differences were considered to be significant at P<0.05.


Data Collection Summary:

Timing of Measurements

  • Resting energy expenditure (REE) and EE after the consumption of the test beverage for 120 minutes were measured
  • The time schedule at the metabolic ward was as follows:
    • Bed at 11:00 p.m. on the previous night
    • Rising at 6:00 a.m.
    • Bathroom, rest in a reclining chair for 30 minutes, collection of expired gas for five minutes to measure resting energy expenditure (REE)
    • Consumption of the test beverage in five minutes
    • Collection of expired gas for five minutes followed by the consumption every 30 minutes for 120 minutes to measure EE in the resting condition.

Dependent Variables

Energy expenditure was measured by the collection of expired gas for five minutes in a Douglas bag. The volume was measured with a gas meter and carbon dioxide and oxygen contents were analyzed with a gas monitor.  

Independent Variables

The treatments were water, oolong tea and green tea, with consumption of the test beverage for 120 minutes.
  • Concentration of caffeine, flavanols and other polyphenols in the oolong tea and the green tea were analyzed by HPLC with UV detection at 280nm. Analysis was performed with a Cosmosil 5PE-MS column.
  • Compounds were eluted at a flow rate of 2ml per minute using a gradient program
  • The quantification of caffeine, flavanols and other polyphenols was determined using standard calibration curves for known compounds purchased commercially
  • Other polyphenols were quantified using a calibration curve that was derived from polyphenols that had been isolated from tea by HPLC.
Description of Actual Data Sample:
  • Initial N: 11 women
  • Attrition (final N): 11 women
  • Age: Mean age 20±1 years
  • Ethnicity: Japanese
  • Other relevant demographics: Mean height 163.4cm±0.9cm
  • Anthropometrics: Mean BMI of 21.1kg/m2±0.8kg/m2, range (18.2kg/m2 to 25.9kg/m2)
  • Location: Japan.


Summary of Results:

Key Findings

  • REE were similar among the three treatments (206.6kJ±3.7kJ, 207.8kJ±4.1kJ and 211.2kJ±3.7kJ per hour for oolong tea, green tea and water treatment
  • Energy expenditure after the consumption of water was constant around the REE level for 120 minutes, energy expenditure after the consumption of oolong tea or green tea increased immediately (EE at 30 minutes: P<0.01) and gradually up to 90 minutes, then maintained until 120 minutes
  • The maximum value of EE after the consumption of oolong tea and green tea were at 90 minutes: 237.3kJ±10.1kJ and 223.2kJ±3.9kJ per hour
  • The values of EE at 60 and 90 minutes after the consumption of oolong tea were significantly higher than those after the consumption of water (P<0.05)
  • The cumulative increases of EE after the consumption of oolong tea, green tea or water above REE was 110.7kJ±17.7kJ, 49.5kJ±0.4kJ and 11.2kJ±1.1kJ per two hours
  • The cumulative increases of EE for 120 minutes were significantly increased 10% and 4% after
    the consumption of oolong tea and green tea, respectively
  • REE was not significantly different among the treatments (0.82±0.01, 0.81±0.01, and 0.82±0.01 for oolong tea, green tea and water).
Author Conclusion:

The results from this study suggest that oolong tea increased energy expenditure and the factor was not only caffeine or EGCG but some kind of polymerized polyphenols.

Funding Source:
University/Hospital: University of Tokushima School of Medicine
Reviewer Comments:
  • Small sample size
  • Only women were studied.
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? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? No
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
  3.2. 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
  3.4. 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? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  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%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  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
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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
  5.4. 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? N/A
  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? 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? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? 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
  7.3. 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? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? 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
  8.1. 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)? 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? No
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