This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Food Intake Response to Short-Term Modifications of Metabolism in Humans (NCT02939404), a randomized na study. The primary outcome is 24-hour Energy Expenditure (kcal).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02939404 |
| Phase | NA |
| Condition | Healthy Volunteers |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 54 |
| Arms in the primary outcome | n/a |
| Lead sponsor | National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns healthy volunteers. The eligibility description specifies healthy people ages 18-55, and the registry record lists enrollment of 54. The intended setting is controlled metabolic-chamber assessment rather than a comparison of clinical treatment in patients with a stated disease.
Intervention
The registered conditions vary chamber temperature and eating instructions. The condition descriptions include a chamber at room temperature, 24°C, or a cooler chamber, and either a fixed eucaloric diet or an ad libitum diet in which participants choose how much to eat. A fasting condition at 24°C is also listed.
Comparator
The study is randomized and uses a crossover model. Its conditions therefore include comparisons between different temperature and diet settings rather than only a parallel comparison of separate groups. The registry record does not report the detailed randomized sequence or the statistical method used to compare conditions.
Primary question
The registered primary endpoint is 24-hour energy expenditure, measured in a whole-room calorimeter. The objectives also concern food intake in response to changes in metabolism and cooling. However, the registry record does not report analyzed primary-endpoint results or a numerical food-intake result. The registered primary outcome is energy expenditure, not food intake.
3. Trial Design
The registry record describes a randomized, unmasked crossover study of healthy volunteers. Enrollment is listed as 54, and the study status is completed. The record gives a start date of 2017-04-27 and a primary completion date of 2024-06-24. These dates describe the registry record; they do not provide outcome results or details of when individual participants completed each condition.
The study description says participants will stay at NIH for 20 days. It outlines 24-hour periods in a metabolic chamber at normal room temperature or cooler, with fixed food intake on some occasions and ad libitum intake on others. The intervention list also includes fasting. The primary endpoint timeframe names chamber conditions on days 6, 10, 14, 18, and 21. The planned procedures include health assessments, blood and urine collection, a body-composition scan, exercise testing, and use of an ingestible sensor and a wearable recorder.
The condition descriptions are not wholly consistent about temperature. The arm titled “Chamber at 19°C, fixed diet” describes a cold temperature of 16C, while the other cold-condition descriptions refer to 19°C. This discrepancy makes the exact temperature for that condition unclear from the registry record. The record does not report the ordering rules, washout arrangements, or the detailed allocation sequence.
The brief summary mentions follow-up visits at six months and “one,” but that description is incomplete in the registry text. Weight change at 6 months and 12 months is listed as a secondary outcome. How those follow-up outcomes were measured and analyzed is not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Chamber at 24°C, Fixed Diet
| Stage | Chamber at 19°C With Fixed Diet First | 2. Chamber at 19°C, ad Libitum Diet First |
|---|---|---|
| STARTED | 24 | 30 |
| COMPLETED | 19 | 27 |
| NOT COMPLETED | 5 | 3 |
Chamber at 24°C, ad Libitum Diet
| Stage | Chamber at 19°C With Fixed Diet First | 2. Chamber at 19°C, ad Libitum Diet First |
|---|---|---|
| STARTED | 24 | 30 |
| COMPLETED | 19 | 27 |
| NOT COMPLETED | 5 | 3 |
Reasons for not completing this period:
| Reason | Chamber at 19°C With Fixed Diet First | 2. Chamber at 19°C, ad Libitum Diet First |
|---|---|---|
| Adverse Event | 2 | 1 |
| Withdrawal by Subject | 3 | 2 |
Chamber at 19°C, Fixed Diet
| Stage | Chamber at 19°C With Fixed Diet First | 2. Chamber at 19°C, ad Libitum Diet First |
|---|---|---|
| STARTED | 24 | 30 |
| COMPLETED | 19 | 27 |
| NOT COMPLETED | 5 | 3 |
Chamber at 19°C, ad Libitum Diet
| Stage | Chamber at 19°C With Fixed Diet First | 2. Chamber at 19°C, ad Libitum Diet First |
|---|---|---|
| STARTED | 24 | 30 |
| COMPLETED | 19 | 27 |
| NOT COMPLETED | 5 | 3 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Chamber at 19°C With Fixed Diet First | 2. Chamber at 19°C, ad Libitum Diet First | Total |
|---|---|---|---|---|
| Participants analysed | 24 | 30 | 54 | |
| Age, Continuous | years | 34.9 (SD 9.4) | 37.8 (SD 10.9) | 36.5 (SD 10.3) |
| Sex: Female, Male: Female | Participants | 10 | 12 | 22 |
| Sex: Female, Male: Male | Participants | 14 | 18 | 32 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 14 | 19 | 33 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 3 | 5 | 8 |
| Race (NIH/OMB): White | Participants | 2 | 2 | 4 |
| Race (NIH/OMB): More than one race | Participants | 1 | 0 | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 4 | 4 | 8 |
6. Primary Endpoint
The registry lists the primary outcome as 24-hour Energy Expenditure (kcal), measured over Days 6 (Chamber at 24°C, fixed diet), 10(Chamber at 24°C, ad libitum diet), 14(Chamber at 19°C, fixed or ad libitum diet), 18(Chamber at 19°C, fixed or ad libitum diet), and 21(Chamber at 24°C, fasting).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | kcal |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is 24-hour energy expenditure in kcal, measured during a 24-hour period in a whole-room calorimeter. Energy expenditure describes energy used by the body over the measured period. The endpoint is recorded as a mean with standard deviation, indicating that the intended summary describes the average measurement and its variability.
In this study, energy expenditure is relevant because the objectives concern how changes in metabolism relate to food intake. Chamber temperature and diet conditions are intended to alter or assess energy use under controlled circumstances. A whole-room calorimeter provides a setting for measuring energy expenditure across the stated 24-hour period, rather than relying only on a brief measurement.
The endpoint timeframe identifies measurements under chamber conditions on days 6, 10, 14, 18, and 21. These points include room-temperature fixed-diet and ad libitum conditions, cooler conditions with fixed or ad libitum diets, and room-temperature fasting. The registry record does not report the corresponding mean energy-expenditure values, standard deviations, confidence intervals, or inferential test results. It therefore does not show the magnitude or precision of any difference between conditions.
Energy expenditure is not the same measure as food intake. Although the study objectives include how much participants eat, the registered primary outcome is energy expenditure. The listed secondary outcomes include other metabolic and hormonal measures, along with weight change at follow-up.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clear measurement focus: mean 24-hour energy expenditure under specified chamber and diet conditions. It also identifies the design as randomized and crossover. Those features describe how the study was structured, but they do not establish what the results were. The record lists 0 analyses, and it contains no posted primary-outcome estimates or associated uncertainty measures. No direction or size of an energy-expenditure contrast can therefore be interpreted from the registry record.
A crossover design can support comparisons within participants, because a participant may experience more than one study condition. In general, that can reduce the influence of stable differences between people when conditions are compared. A valid analysis still depends on the actual sequence of conditions, the measurements obtained, and the statistical model. The detailed sequence and analysis approach are not reported in the registry record, so it is not possible to assess how those features were handled.
The study's stated objectives concern food intake after changes in metabolism and cooling, but the primary registered outcome is energy expenditure. These are related concepts, not interchangeable outcomes. The primary endpoint alone would not establish how much food participants ate, and no numerical intake result is reported in the registry record. The listed secondary outcomes include respiratory quotient, hormones, core body temperature, and weight change at follow-up, but results for those outcomes are not reported either.
Precision cannot be assessed without the outcome estimates and their uncertainty. In general, a confidence interval describes a range of values compatible with the data and analysis under its assumptions. A narrow interval indicates greater precision than a wide interval, while the estimate's substantive meaning depends on the outcome scale and comparison. The registry record does not report confidence intervals for the primary endpoint.
The safety counts are a separate kind of result. The registry lists no serious adverse events or deaths in either displayed group, and lists other adverse events in both groups. These counts do not provide an estimate of the primary endpoint, and they do not establish a causal relation between a condition and an event. The event-count details and limitations are discussed separately.
Accordingly, the record supports interpretation of the planned endpoint and design, not an efficacy or effect conclusion. It is not possible to say from the posted results whether energy expenditure differed across conditions, how precisely it was estimated, or whether food intake changed.
9. Statistical Methods Explained
The registry record labels the primary outcome as a continuous measure summarized by a mean and standard deviation. The mean represents the average energy-expenditure measurement within the group or condition being summarized. The standard deviation describes variation among measurements around that average. It is not the same as the standard error, which describes the precision of an estimated mean, and it is not itself a confidence interval.
A comparison of means asks how the measured outcome differs between conditions. The interpretation depends on which conditions are compared and on the analysis model. For this crossover study, observations may be linked because a participant can experience multiple conditions. General statistical methods for crossover data account for this within-participant relationship rather than treating every condition measurement as independent. Whether and how the registry analysis accounted for that structure is not reported in the registry record.
Randomization refers to assignment by a chance-based process. It can help prevent systematic differences in assigned conditions, but it does not itself resolve every source of bias or analysis problem. Masking is listed as none, meaning the registry does not describe masking. In general, lack of masking can affect behavior, measurement, or assessment depending on the outcome and study procedures. The record does not report whether any outcome assessment was conducted without knowledge of condition.
In general, confidence intervals communicate uncertainty around an estimate. Their interpretation depends on the model and assumptions used to calculate them. A confidence interval that includes values on both sides of a reference value may be compatible with more than one interpretation, and a p-value addresses a different question from the size and precision of an effect. The registry record does not report a primary-endpoint estimate, confidence interval, p-value, or statistical test, so none of these can be interpreted for the study outcome.
Variation in a continuous outcome may be greater than expected under a simple model. In general, over-dispersion means observed variability exceeds what a model assumes. Ignoring it can make uncertainty appear too small. Whether over-dispersion was assessed or relevant to the primary endpoint is not reported in the registry record. The outcome is listed as a mean with standard deviation; no distributional checks or variance model are described.
The record includes planning assumptions for sample-size illustrations: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The stated effect to detect is a fraction of the observed effect. Such calculations are planning illustrations, not results from the trial. They are not observed power, and they do not establish the power achieved by the completed study. The registry record does not report the trial's own sample-size justification or the numerical results of any planning illustration.
The stated planning approach refers to equal allocation between two arms, while the study is described as a crossover with several conditions. That planning assumption should not be mistaken for a description of the actual condition sequence or the primary analysis. The registry record does not report whether planning reflected the crossover structure, within-participant correlation, or the actual planned comparisons.
The primary endpoint is measured at several specified time points and conditions. In general, repeated measurements can be analyzed using a model that recognizes their relationship and accounts for condition, period, and participant effects as appropriate to the design. Those are general methodological considerations, not a description of the analysis performed in this study. The model, contrast definitions, covariates, and handling of period or sequence effects are not reported in the registry record.
Multiplicity arises when several outcomes, time points, or comparisons are tested. In general, conducting many tests can increase the chance of at least one apparently notable result when there is no underlying effect. Researchers may address this by specifying a primary comparison in advance or by adjusting interpretation or testing across analyses. The registry lists 10 outcome measures and 0 analyses, but does not report a multiplicity strategy or a set of prespecified contrasts.
Missing observations can affect both the estimate and its precision. In general, the consequences depend on why measurements are missing and whether the analysis assumptions about missingness are reasonable. Methods may use complete observations, model-based approaches, or other strategies, but no approach can be attributed to this study from the registry record. The amount and pattern of missing primary-outcome data and the method for handling them are not reported.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 10 outcome measures, including the primary energy-expenditure outcome and secondary measures of respiratory quotient, hormones, core body temperature, and weight change at follow-up. Several conditions and time points are named for the primary endpoint. A study with multiple outcomes or comparisons raises a general multiplicity concern: the chance of an apparently unusual finding can increase as more tests are considered. The registry record does not report a multiplicity adjustment, a hierarchy for secondary outcomes, or the set of comparisons designated as primary.
The record lists 0 analyses. It therefore does not provide an analyzed result set from which to judge whether all outcomes and comparisons were reported. The statistical analysis plan, including any prespecified contrasts or rules for interpreting secondary outcomes, is not reported in the registry record.
The registry does not report how many primary-outcome measurements were missing, why any measurements may have been missing, or how missing observations were handled. In general, missingness can affect both the estimated condition differences and their uncertainty. Interpretation depends on the amount, pattern, and cause of missing data, as well as the assumptions and methods used in analysis. Those details are not reported in the registry record.
The analysis population is also not reported in the registry record. It is not stated whether the primary analysis included all randomized participants, only participants completing specified conditions, or another defined population. The enrollment entry alone does not establish the number with usable measurements or the population used for analysis. The statistical plan and analysis populations are not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Chamber at 19°C With Fixed Diet First | 0 | 24 | 0.0% |
| 2. Chamber at 19°C, ad Libitum Diet First | 0 | 30 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Chamber at 19°C With Fixed Diet First | 0 of 24 |
| 2. Chamber at 19°C, ad Libitum Diet First | 0 of 30 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Chamber at 19°C With Fixed Diet First | 2 of 24 |
| 2. Chamber at 19°C, ad Libitum Diet First | 1 of 30 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Chamber at 19°C With Fixed Diet First | 2. Chamber at 19°C, ad Libitum Diet First |
|---|---|---|---|
| Gastroesophageal reflux disease symptoms at Chamber at 24°C, fixed diet | Gastrointestinal disorders | 2 of 24 | 0 of 30 |
| Gastroesophageal reflux disease symptoms at Chamber at 19°C, fixed diet | Gastrointestinal disorders | 0 of 24 | 1 of 30 |
The registry lists serious adverse event counts for two displayed groups: “Chamber at 19°C With Fixed Diet First” and “2. Chamber at 19°C, ad Libitum Diet First.” Each group has 0 serious adverse events and 0 deaths. The record lists 2 other adverse events in the fixed-diet-first group and 1 in the ad-libitum-diet-first group. The corresponding at-risk counts are 24 and 30.
These are counts, not estimates of the primary endpoint. The record does not describe the other adverse events in the information available for this summary, so their type, severity, timing, and relation to study conditions cannot be assessed. It also does not state whether event counts represent participants with events or event occurrences. A count alone does not establish that a condition caused an event.
Zero recorded serious events in these groups means that none are listed in the registry record for those categories and groups. It should not be read as proof that serious events are impossible, or as evidence about safety beyond the recorded study data. The record does not provide further context about event surveillance, duration of risk observation, or how safety events were adjudicated.
12. What the Result Does, and Does Not, Mean
The registry record describes a controlled study of energy expenditure under different chamber-temperature and diet conditions. Its randomized crossover design and 24-hour calorimetry endpoint address how measured energy use varies across the planned conditions. The registered objective also concerns food intake, but the primary outcome is energy expenditure rather than food intake itself.
The posted results do not include analyzed primary-outcome values. The record lists 0 analyses and does not report condition means, standard deviations, confidence intervals, or p-values for energy expenditure. It therefore cannot establish whether energy expenditure was higher, lower, or similar under any particular condition, nor how precise a comparison may be. No conclusion about the size or practical importance of an effect can be drawn from the record.
The secondary outcomes broaden the study's measurement scope, including respiratory quotient, hormone measures, core body temperature, and weight change at 6 months and 12 months. Their listing indicates intended assessment, not a reported finding. Their estimates and uncertainty are not reported in the registry record.
The safety entries describe recorded event counts in the displayed groups, but they do not replace outcome analysis and do not determine whether the study conditions affected energy expenditure or food intake. In general, event counts require context about event definitions, observation time, and the people included. That context is limited in the registry record.
The record does support a description of the research question, design, endpoint, and listed safety counts. It does not support claims that a condition changed energy expenditure or eating behavior, that findings apply beyond the enrolled healthy-volunteer population, or that effects persisted at follow-up. Those conclusions would require analyzed results and appropriate uncertainty estimates, which are not reported in the registry record.
13. Why This Trial Matters Statistically
This study is statistically notable for combining a randomized crossover design with repeated measurements of a continuous metabolic outcome. In general, crossover designs can make within-participant comparisons informative because each participant may contribute measurements under multiple conditions. At the same time, the analysis needs to reflect the dependence among those measurements. The registry record identifies the design but does not report the model used to address it.
The conditions vary both temperature and diet, and the primary endpoint is measured across named chamber periods. That structure makes careful definition of the comparison important. A temperature contrast, a diet contrast, and a combined condition contrast answer different statistical questions. The registry record does not identify the primary contrast or explain how these factors were separated in analysis.
The distinction between the study objective and registered primary endpoint also matters. The objectives concern food intake and metabolic change, whereas the primary registered outcome is 24-hour energy expenditure. Interpreting one measure as if it were the other would overstate what the endpoint can answer. The listed secondary measures provide additional intended context, but no analyses are reported.
Finally, registry completeness affects how much can be learned from a completed study. Design and endpoint descriptions are available, and safety counts are listed, but analyzed results, uncertainty estimates, missing-data handling, and the statistical plan are not reported in the registry record. Without those elements, readers can assess the structure of the question but not the strength or precision of its answers.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most important limitation for statistical interpretation is that the registry record contains no analyzed primary-endpoint results. It lists 0 analyses and provides no energy-expenditure means, standard deviations, condition contrasts, or uncertainty estimates. As a result, the magnitude, direction, and precision of the primary outcome cannot be assessed.
The design description has an internal temperature inconsistency. The arm title for the fixed-diet cold condition says 19°C, while its description says 16C. This leaves the exact temperature for that condition unclear. The detailed sequence of conditions and the analysis model are also not reported, limiting assessment of how the crossover structure was implemented and analyzed.
The registered objectives include food intake, but the primary endpoint is energy expenditure. The registry does not report a numerical food-intake result, so the primary endpoint cannot be used to infer the eating response. Secondary outcomes are listed, but their results are not reported.
The statistical analysis plan, multiplicity approach, analysis population, and missing-data methods are not reported in the registry record. The record also does not provide enough detail to assess how measurements were handled across periods or whether the analysis accounted for within-participant correlation. Follow-up is described incompletely in the brief summary, although weight change outcomes at 6 months and 12 months are listed.
These limitations concern what can be interpreted from the registry record; they do not establish that the study lacked these procedures or that the data were not collected. They indicate that the relevant details and results are not reported in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Food Intake Response to Short-Term Modifications of Metabolism in Humans — NCT02939404.
- Registry record last updated 2025-07-04; status last verified 2024-07-03.
- Results first posted 2025-07-04.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The registry record describes NCT02939404, “Food Intake Response to Short-Term Modifications of Metabolism in Humans,” with an official title focused on energy-intake response to short-term alterations of energy expenditure. The study is listed as randomized, unmasked, and crossover, with healthy volunteers and enrollment of 54. Its status is completed.
The registered primary outcome is mean 24-hour energy expenditure in kcal, measured in a whole-room calorimeter under specified chamber and diet conditions. The intervention descriptions include room-temperature and cooler conditions, fixed and ad libitum diets, and fasting. The record lists 10 outcome measures and 0 analyses.
Serious adverse event counts are 0 in each displayed group, with other adverse event counts of 2 and 1, and deaths of 0 in both groups. The registry record does not report analyzed primary-outcome results, statistical methods, missing-data handling, or the analysis population. The temperature description for the fixed-diet cold condition is inconsistent with its arm title.