EE: Caffeine and Other Stimulants (2014)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  1. To clarify any differences in basal metabolic rate (BMR) and themogenic response to caffeine in individual obese women
  2. To determine whether BMR differences affected weight loss, and basal and resting metabolic rate at 30 min after a caffeine loading test (4 mg/kg ideal body weight (IBW).
Inclusion Criteria:
  1. Understand and give written consent
  2. Healthy, adult women, assessed as obese and 10 age-matched controls
  3. Habitual drinkers of coffee or Japanese tea with milk to moderate caffeine intake (100-200 mg/d caffeine) (assessed by answers to questionnaire on consumption)
  4. Not on any medications.
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria
  3. Diseases in subjects that were excluded: diabetes mellitus and hypertension
  4. Subjects who had a habitual intake of more caffeine than that from coffee, tea, Japanese tea and cola beverages that corresponded to 3 daily cups of coffee (>300 mg/d caffeine) or 4 daily cups of Japanese tea (>300 mg/d caffeine).
Description of Study Protocol:


  • Ht measured? Yes, initial method not mentioned
  • Wt measured? Yes, initial method not mentioned
  • Skin-fold thicknesses: At the biceps, triceps, subscapular, and supr-iliac regions measured using calipers
  • Lean body mass measured? Yes; calculated by subtracting body fat from body weight.


  • Monitored heart rate? Not mentioned
  • Body temperature? Not mentioned
  • For all subjects (subjects spent the night at the university hospital)

Resting energy expenditure

  • IC type: Closed-circuit indirect calorimeter with a mouth piece
  • Equipment of Calibration: Not mentioned
  • Coefficient of variation using std gases: Not mentioned
  • Rest before measure (state length of time rested if available): BMR measured 30min after awoke in the morning; RMR measured 30 min after caffeine loading (4 mg/kg IBW).
  • Measurement length: BMR values were obtained as the means of 10 min measurement period.
  • Steady state: Not mentioned
  • Fasting length: Subjects abstained from coffee and Japanese tea 24 h prior to initiation of each test.
  • Exercise restrictions: Not mentioned; obese subjects were requested to follow an exercise regimen (mean 10,000 steps/d; mean 1255 kJ (300 kcal/d) for 2 months
  • Room temp: Controlled at 22-24 degree C.
  • No. of measures within the measurement period: BMR measured –means of 10 min. measurement period; then after caffeine loading, RMR measured 30 min after, also mean of 10 min. measurement period
  • Were some measures eliminated? Not mentioned
  • Were a set of measurements averaged? BMR measured –means of 10 min. measurement period; then after caffeine loading, RMR measured 30 min after, also mean of 10 min. measurement period
  • Coefficient of variation in subjects measures? Not mentioned
  • Training of measurer? Not mentioned
  • Subject training of measuring process? Not mentioned.


  • In a 2-month treatment period, obese patients were asked to follow a daily 4184-5020 kJ diet (60% CHO, 23% protein, and 17% fat) (104.6 kJ (25 kcal)/kg ideal body weight).
  • Intervening factor: It was not mentioned if physical activity was measured in the 10 lean controls.
Data Collection Summary:
  1. Body fat (% body fat), Lean body mass (LBM), Weight
  2. BMR (kJ/min), RMR (kJ/min)
  3. Daily food intake and exercise.

Blinding used: No.

Description of Actual Data Sample:
  • N=136 women, obese,
  • Mean age, y: 42.6±1.4
  • Mean duration of obesity, y: 4.6±1.7.

Control Sample

  • N=10 women, age-matched lean controls
  • Mean age, y: 43.1±1.5.

Statistical tests

Data provided as means ±SD; Data analyzed by one-way or two-way ANOVA. After justification by ANOVA, the Bonferroni T-test was performed. Single correlations were also calculated between the different variables.

Summary of Results:


Obese women (n=136) Mean±SD

Wt, kg

Ht, cm data not avail





Lean body mass (kg)


Fat mass

not provided

Lean women (age-matched controls) (n=10) Mean±SD

Wt, kg


Ht, cm

data not provided




Lean body mass 40.0±1.6

Fat mass

not provided



  • KJ/min: 3.57±0.46
  • Kcal/min: 0.85±0.12
  • Range, kJ/min: 2.61-4.27
  • Range, kcal/min: 0.62-1.0
  • BMR/LBM, kJ/min/kg: 0.77±0.01
  • BMR/LBM,kcal/min/kg: 0.2±0.002
  • BMR/LBM Range
    KJ/min/kg LBM:
    Kcal/min/kg LBM: 0.013-0.023.


  • KJ/min: 3.32±0.11
  • Kcal/min: 0.79±0.03
  • Range, kJ/min: 3.18-3.59
  • Range, kcal/min: 0.76-0.86
  • BMR/LBM, kJ/min/kg: 0.083±0.009 LBM
  • BMR/LBM,kcal/min/kg: 0.29±0.002 LBM
  • BMR/LBM Range
    kJ/min/kg LBM:
    kcal/min/kg LBM: 0.017-0.022.


  • KJ/min: 4.06±0.51
  • Kcals/min: 0.97±0.12
  • Range, kJ/min: 2.75-5.30
  • Range, kcal/min: 0.66- 1.3
  • Percentage, %: 13.8±6.2
  • Percentage Range, %: 0.7-24.8.


  • Percentage, %: 15.2±5.0
  • Percentage Range, %: 9.6-23.0.

Values for BMR, BMR/LBM and the thermogenic response to caffeine for the obese subjects did not differ significantly from the values for the lean controls.

After the 2-month treatment period, among the obese subjects, body weight had significantly (P<0.001) decreased from 73.2±3.8 kg to 69.4±2.3 kg, and the BMI had decreased from 30.9±1.5 to 29.3±1.0 kg/m2 (P<0.001), with percentage of body fat decreasing from 36.7±1.4% to 33.7±1.1% (P<0.001).

The BMR was significantly correlated with reduction in body weight (R=0.32, P<0.001). The BMR/LBM was also significantly correlated with body weight (R=0.69, P<0.001).

There was also a significant correlation (P<0.001) between the BMR and the thermogenic response to caffeine.

There was no correlation between body weight and initial body weight, BMI, percentage body fat, LBM or duration of obesity. The variable that showed the best correlation with body weight loss was the thermogenic response to caffeine.

The obese subjects were divided into groups based on BMR or thermogenic response to caffeine.

When the criterion of a BMR <3.10 kJ/min (less than 2 standard deviations below the mean of the age-matched lean controls) was used to define an obese group with reduced BMR, 30 obese women were in this category. Their body weight was significantly (P<0.05) decreased, from 72.8±3.8 kg to 70.3±3.5 kg, after 2 months of treatment.

When the criterion of <5.2% of the thermic response to caffeine (less than 2 standard deviations of the mean of the age-matched lean controls) was used to define an obese group with reduced thermogenic response to caffeine, 24 obese women fit in this category. Their body weight was not reduced after treatment (73.6±2.9 kg vs. 72.3±2.4 kg).

There were no significant pre-treatment differences in age, duration of obesity, body weight, BMR, percentage body fat or LBM in these obese groups.

Author Conclusion:

Our findings suggest that there are considerable individual variations in BMR and thermogenic response to caffeine among obese women, although there were no differences between the obese group and the age-matched lean controls.

Findings confirm previous reports of a thermogenic effect of caffeine in humans who have a mild to moderate daily caffeine consumption. As caffeine stimulates thermogenesis in a dose-response way, it is thought that the dose of caffeine used in the study is of critical importance in interpreting the results. We gave a dose of caffeine per IBW in both the obese and lean controls. Therefore, it might be thought that the obese subjects were given less caffeine than the lean controls as the dose was assessed by LBM. However, the thermogenic response to caffeine was similar in both groups. This was consistent with previous findings that showed that the rise in RMR with caffeine (4 mg/kg IBW) was similar in both lean and obese subjects. However, in post-obese subjects, different findings have been reported depending on the dose of caffeine.

Our results also indicate that there were significant correlations between body weight loss and BMR, between body weight loss and BMR/LBM, and between body weight loss and the thermogenic response to caffeine in obese subjects. There was no correlation between body weight loss and duration of obesity, or initial body weight, percentage body fat and LBM.

We found that body weight loss was significant in an obese group with reduced BMR (30 obese subjects) while body weight loss did not occur in an obese group with reduced thermogenic response to caffeine (24 obese subjects), although initial body weight, percentage body fat and LBM did not differ between these two obese groups. The coefficient of correlation (R=0.69) between body weight loss and the thermogenic response to caffeine was much stronger than that between weight loss and BMR (R=0.36), indicating that the thermogencic response to caffeine would be a more appropriate index than BMR to predict body weight loss after treatment in obese women. This result also indicates that obese subjects who have a reduced thermogenic response to caffeine will find it difficult o reduce body weight with conventional diet and exercise treatment. Therefore, such obese subjects should be distinguished as having obesity with reduced thermogenesis.
Funding Source:
Government: Ministry of Education, Science & Culture of Japan
Reviewer Comments:


  • Small sample size of control lean women
  • Did not discuss physical activity restrictions of subjects prior to testing
  • Lack of description of IC steady state, subject training, and training of measurer
  • Did not discuss how initial height and weight measurements were determined (self-reported or measured?)
  • Limited generalizability; sample consisted of women; may not apply to men.
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? 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