EAL

EE: Respiratory Quotient (RQ) (2014)

Citation:

Romijn JA, Godfried MH, Hommes MJ, Endert E, Sauerwein HP. Decreased glucose oxidation during short-term starvation. Metabolism. 1990 May; 39 (5): 525-530.

PubMed ID: 2110608

Study Design:

Time Study

Class:

C - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To evaluate the influence of short-term starvation (16 and 22 hours) on glucose metabolism in healthy subjects.

Inclusion Criteria:

Understand and give written consent
Medical history and physical examination normal
No medications allowed
No family history of diabetes
Within 10% of IBW.

Exclusion Criteria:

Refusal to consent
Not meeting inclusion criteria
Diseases in subjects that were excluded
Medications excluded.

Description of Study Protocol:

Begin fasting at 6 p.m. the night before.

Anthropometric

Height measured? Likely
Weight measured? Likely
Fat-free mass measured? Not specified.

Clinical

Monitored heart rate? Yes
Body temperature? Likely
Medications administered? No.

Resting Energy Expenditure

IC type: SensorMedics 2900
Equipment Calibration: Yes
Coefficient of variation using std gases: Yes, less than 1%
Rest before measure (state length of time rested if available): 7 a.m. to 4:30 p.m.
Measurement length: 30 minutes
Steady state: Eliminated first 10 minutes for stabilization
Fasting length: 16 hours, 22 hours
Exercise restrictions XX hour prior to test? Yes
Room temperature: Not specified
Number. of measures within the measurement period: One-minute to 30-minute measure
Were some measures eliminated? First 10 minutes
Were a set of measurements averaged? Yes 30 one-minute measure
Coefficient of variation in subjects measures? Yes
- Period 1: 6.4% O₂ and 9.1% CO₂
- Period 2: 25.2% O₂ and 7.7% CO₂
Training of measurer? Likely
Subject training of measuring process? Yes.

Dietary

Consume 11g to 15g pro; 200g to 250g CHO three days before the study.

Data Collection Summary:

Outcome(s) and other measures

Measured REE [(VO₂ l/min), VCO₂ (l/min; ml/kg/min), RQ, ventilation (l/min)]
Glucose and lipid plasma glucose concentration, glucose turnover, insulin metabolism, free fatty aacid concentration, aceoacetate and 3-hydroxybutryate
Independent variables of weight, height, age, BMI

Blinding used: No

Description of Actual Data Sample:

N=12 health male volunteers
Mean age: 30±1 years (SEM)
Age range: 22 to 44 years
Statistical tests:
- Paired T-test
- Correlation analysis performed by Spearman rank test.

Summary of Results:

Anthropometric (SEM)

Men	Mean±SE
Weight, kg	75.5±2
Height, cm	182±2
BMI	21.6±2.7

RQ RESULTS

CO₂ production decreased between 16-hour and 22-hour production (2.63ml±0.06ml to 2.47ml±0.03ml kg per minute (P<0.01) whereas O₂consumption did not change significantly during the same time interval (3.43ml±0.07ml vs. 3.42ml±0.08ml per kg per minute)
Therefore, RQ decreased from 0.77±0.01 to 0.72±0.01 (P<0.005)
Individual 16-hour fasting RQ range was from 0.72 to 0.80 and 22-hour fasting RQ range was 0.65 to 0.79.

Author Conclusion:

As stated by the author in body of report:

In our study, the whole process of ketogenesis and subsequent oxidation has a RQ of 0.70 and the RQ for ketogenesis per se is zero, accumulation of ketone bodies without oxidation and urinary excretion of ketone bodies may cause a decrease in RQ
This study shows that net glucose oxidation is depressed within 24 hours of fasting and illustrates that the “post-absorptive” state is an ill-defined metabolic condition. Several physiological mechanisms may be implicated in the regulation of glucose oxidation during short-term starvation, like decreased insulin action and inhibition of glucose oxidation by ketone bodies, even in relatively low concentrations.

Funding Source:

Reviewer Comments:

Strengths

Excellent indirect calorimetry measurement protocol
Reports individual RQ ranges.

Generalizability/Weaknesses

Questionable validity of indirect calorimeter
Generalizable to young-middle aged, lean healthy adults; may not reflect overweight and obese population fasting
Ethnicity not discussed but likely Caucasian
Study biases includes convenience sampling and may include more disciplined subjects who can fast for a whole day.

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?		???
	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