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 The Effects of Leucine on Body Weight (NCT00683826), a randomized na study. The primary outcome is Effects on Weight.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00683826 |
| Phase | NA |
| Condition | Overweight, Obesity |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Triple |
| Enrollment | 8 |
| Arms in the primary outcome | 3 |
| Lead sponsor | Columbia University |
| Results posted | Yes |
2. Clinical Question
The study asks whether oral leucine supplementation is associated with changes in body weight and other metabolic measures in people with overweight or obesity. Its stated rationale is that benefits observed with protein-rich diets, and in mice given leucine, might relate to increased leucine intake. The registry describes the study as a pilot intended to assess possible effects in humans and to inform the design of more definitive trials.
Population
People described in the registry as overweight or obese. Further eligibility criteria and participant characteristics are not reported in the registry record.
Intervention
The listed intervention arms are leucine at 4 grams and 8 grams. The registry also lists a liquid meal and describes a control drink with no leucine.
Comparator
The 0-gram leucine control arm is the stated comparison condition. Details about how the liquid meal relates to each study condition are not reported in the registry record.
Primary question
What body-weight means were recorded after the stated four-week timeframe for the leucine arms and the control arm? The posted results are descriptive arm summaries, not a reported test of a treatment contrast.
The study description also names basal metabolic rate, glucose tolerance or insulin sensitivity, and circulating LDL-cholesterol as areas of interest. Energy expenditure is listed as a secondary outcome. The available primary outcome is titled “Effects on Weight” and is measured in kilograms. Although the registry lists a crossover model, the record does not explain the sequence of conditions, the timing of measurements between conditions, or whether a washout period was used. Those details are important to interpreting what the arm-level weight summaries represent.
3. Trial Design
The registry identifies the study as randomized, triple-masked, and crossover, with an enrollment of 8. Columbia University is listed as the sponsor. The study is marked completed; its recorded start is 2007-05 and its primary completion is 2010-02. The phase is listed as NA.
The intervention descriptions refer to leucine doses of 4 grams and 8 grams, as well as a control drink containing no leucine. The registry also lists a liquid meal. Its arm descriptions call the study a triple-arm design and say participants would be randomized into three groups, while the design field identifies a crossover model. The record does not reconcile these descriptions or explain whether participants received conditions in a sequence or were assigned to a single group. It also does not report the randomization procedure, allocation concealment, treatment sequence, or masking roles.
For the weight outcome, the posted arm summaries report a mean and standard deviation for each condition. The recorded arm-specific sample sizes are 7 for Leucine 4 Grams, 8 for Leucine 8 Grams, and 8 for Leucine 0 Grams-control. These counts should be read as the outcome-summary denominators; the registry does not explain how they relate to enrollment or to the crossover designation. The analysis population, participant flow, and handling of repeated measurements are not reported in the registry record.
The primary outcome timeframe is 4 weeks. Energy Expenditure is listed as a secondary outcome, but detailed results for that outcome are not included in the registry record for this analysis. The registry lists 3 outcome measures and 0 analyses. A protocol-level statistical analysis plan, information about interim analyses, and a sample-size justification for the trial itself are 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.
Overall Study
| Stage | All Study Participants |
|---|---|
| STARTED | 8 |
| 0g Leucine | 8 |
| 8g Leucine | 8 |
| 4g Leucine | 7 |
| COMPLETED | 7 |
| NOT COMPLETED | 1 |
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 | Leucine 4 Grams | Leucine 8 Grams | Leucine 0 Grams-control | Total |
|---|---|---|---|---|---|
| Participants analysed | 2 | 3 | 3 | 8 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 2 | 3 | 3 | 8 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 | 0 |
| Age Continuous | years | 35 (SD 7) | 40 (SD 7) | 45 (SD 7) | 40 (SD 7) |
| Sex: Female, Male: Female | Participants | 1 | 3 | 3 | 7 |
| Sex: Female, Male: Male | Participants | 1 | 0 | 0 | 1 |
| Region of Enrollment: United States | participants | 2 | 3 | 3 | 8 |
6. Primary Endpoint
The registry lists the primary outcome as Effects on Weight, measured over 4 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | kilograms |
| Endpoint classification | Continuous Endpoint |
The primary outcome is titled “Effects on Weight.” It measures body weight in kilograms, with the registry specifying a mean and standard deviation and a timeframe of 4 weeks. Weight is a continuous measure: its value can fall across a range rather than being limited to categories such as improved or not improved. Reporting a mean gives a summary of the group’s recorded values, while the standard deviation describes how dispersed those values are around the mean.
The registry reports a mean weight of 93.4 kilograms (standard deviation 16.8) for Leucine 4 Grams, based on 7 participants; 91.7 kilograms (standard deviation 17.2) for Leucine 8 Grams, based on 8 participants; and 91.9 kilograms (standard deviation 15.2) for Leucine 0 Grams-control, based on 8 participants. The outcome description does not say whether these are changes from baseline or measurements at the end of the stated timeframe. The baseline measurement, endpoint measurement schedule, and definition of the analyzed value are not reported in the registry record.
Weight is relevant to the study’s stated question about whether leucine supplementation is associated with body-weight changes. However, arm means alone do not establish how much change occurred within participants or whether conditions differed beyond chance variation. Those interpretations require details about the measurement schedule and an appropriate analysis, neither of which is reported for this endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted results give descriptive weight summaries for the three named conditions. The mean is 93.4 kilograms in the 4-gram arm, 91.7 kilograms in the 8-gram arm, and 91.9 kilograms in the 0-gram control arm. The corresponding standard deviations are 16.8, 17.2, and 15.2. These statistics describe the reported arm-level values; they do not, on their own, quantify a treatment effect or establish evidence for a difference between conditions.
The record does not report an inferential analysis for the weight outcome. It lists 0 analyses, and no confidence interval, p-value, adjusted estimate, or test result is available in the record. Therefore, the precision of any difference between leucine and control cannot be assessed from the posted means and standard deviations alone. The standard deviations reflect variation among recorded values, not uncertainty around a treatment contrast. A confidence interval for a contrast would address that uncertainty, but none is reported.
Interpretation also depends on what the arm summaries represent. The design field says crossover, while the arm descriptions refer to randomization into three groups. In a crossover study, participants generally contribute measurements under more than one condition, so analysis often needs to account for within-participant pairing and the order of conditions. In a parallel-group study, each participant contributes to an assigned condition. The registry does not clarify which structure generated these results, nor does it report a sequence or period analysis. Consequently, the arm-level summaries should not be treated as evidence that the observations are independent or paired.
The reported means are endpoint summaries, but the record does not state whether they are baseline values, follow-up values, or changes from baseline. No baseline weight summaries are reported in the registry record. Without that definition, the summaries cannot be interpreted as weight loss or gain. The four-week timeframe identifies the outcome’s stated measurement period but does not resolve this ambiguity.
The small arm-specific denominators and lack of inferential results mean that the posted data offer limited precision for comparing conditions. This is consistent with the registry’s description of the study as a pilot, but the record does not provide a formal sample-size justification or a protocol-defined interpretation threshold. Any claim about a treatment effect, its statistical significance, or its clinical importance would go beyond the reported results.
These results describe recorded body-weight values in the listed arms. They do not report whether leucine altered weight, whether one dose differed from another, or whether any observed variation reflects a treatment effect. The registry also names other metabolic interests, but the body-weight summaries do not answer those separate questions.
9. Statistical Methods Explained
The registry reports a continuous primary outcome summarized by a mean and standard deviation. These are descriptive statistics. A mean locates the center of the recorded values, while the standard deviation describes their spread. Neither statistic is itself a comparison between treatment conditions. The posted means and standard deviations can characterize each arm, but do not supply a standard error, confidence interval, or test of an arm contrast.
What does a confidence interval add?
In general, a confidence interval expresses the uncertainty around an estimated quantity, such as a difference between conditions. A narrow interval indicates greater precision than a wide interval, given the assumptions of the analysis. For a treatment comparison, the interval also helps show which effect sizes remain compatible with the data and analysis. No confidence interval for the weight outcome is reported in the registry record. The arm means and standard deviations are not substitutes for an interval around a properly defined contrast.
Why does the design description matter?
The record identifies the trial as crossover but describes randomization into three groups. These terms imply different data structures unless the record explains how the design was implemented. In general, a crossover design exposes a participant to multiple conditions over time. Comparisons can then use within-participant information, while accounting for the sequence and period of exposure. A parallel-group design instead compares participants assigned to separate conditions. The choice affects the statistical model, the uncertainty calculation, and the interpretation of the arm summaries.
For a crossover analysis, it would be important to know which participants received which conditions, the order of conditions, when outcome measurements were made, and whether any washout was planned or used. Those details are not reported in the registry record. It also does not state whether the posted means summarize observations from each treatment period or some other value. As a result, the appropriate comparison and its uncertainty cannot be reconstructed from the arm summaries.
What do the standard deviations say?
In general, a standard deviation describes variation among the observations used to calculate a mean. It does not reveal the full distribution of values, identify outliers, or explain the sources of variation. The posted standard deviations accompany the arm means, but the registry does not provide participant-level values or distributional plots in the registry record for this analysis. They should therefore be read as summaries, not as evidence that the outcome follows a particular distribution.
How should the planning calculations be read?
The registry’s stated assumptions describe planning illustrations based on an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is defined as a stated fraction of the observed effect. Such calculations are design illustrations, not observed power and not evidence that a trial of a particular size would produce a result. A planning illustration asks what sample size might be needed under its assumptions; it does not show that a treatment effect is real.
For this continuous endpoint, the registry identifies values as missing or not estimable for a two-arm comparison. Therefore, no usable two-arm comparison is available for interpreting planning outputs from the reported weight summaries. A crossover design would also require assumptions that reflect paired measurements if that was the structure actually used. The registry does not report such a design-specific calculation. Any planning interpretation must remain distinct from the observed results and from the original trial’s design rationale, which is not reported in the registry record.
What can be inferred without a test?
Descriptive summaries show what was recorded in each named arm, subject to the outcome definition and denominators. They do not determine whether an apparent difference exceeds sampling variability. An inferential comparison would require a clearly specified contrast, an analysis model appropriate to the design, and a measure of uncertainty. The registry does not report those elements for the primary weight outcome. No significance conclusion can be drawn from the means and standard deviations alone.
General statistical interpretation also depends on how missing observations were handled and which participants were included in each analysis. The registry reports arm-specific denominators but does not describe exclusions, missing outcome data, or an analysis population. Those omissions limit assessment of the reliability and scope of the descriptive summaries.
10. Confidence Intervals for Each Arm
No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.
| Arm | Participants | Mean | Standard deviation | 95% CI for the mean |
|---|---|---|---|---|
| Leucine 4 Grams | 7 | 93.400 | 16.800 | 77.863 to 108.937 |
| Leucine 8 Grams | 8 | 91.700 | 17.200 | 77.320 to 106.080 |
| Leucine 0 Grams-control | 8 | 91.900 | 15.200 | 79.192 to 104.608 |
R code and output
arm <- c("Leucine 4 Grams", "Leucine 8 Grams", "Leucine 0 Grams-control")
n <- c(7, 8, 8)
m <- c(93.4, 91.7, 91.9)
sp <- c(16.8, 17.2, 15.2)
sd <- sp # posted standard deviations
for (i in seq_along(n)) {
se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}
CARM Leucine 4 Grams 7 93.400 16.800 77.863 108.937
CARM Leucine 8 Grams 8 91.700 17.200 77.320 106.080
CARM Leucine 0 Grams-control 8 91.900 15.200 79.192 104.60811. Multiplicity, Missing Data and Analysis Populations
The registry lists 3 outcome measures and 1 posted secondary outcome, Energy Expenditure. Its study description also mentions metabolic rate, glucose utilization or tolerance, insulin sensitivity, circulating fat levels, and LDL-cholesterol as areas of interest. The registry entries available for this analysis do not include detailed results for those outcomes beyond the primary weight summaries. The registry does not report a hierarchy for interpreting multiple outcomes, a multiplicity adjustment, or a prespecified plan for controlling the risk of false-positive findings across outcomes. Such a plan is therefore not reported in the registry record.
Missing-data handling is also not reported in the registry record. There is no description of missing measurements, reasons for missingness, imputation, or sensitivity analyses. The arm-level denominators are 7, 8, and 8, while the recorded enrollment is 8; the record does not explain the relationship between these figures, especially given its crossover designation. They should not be combined or interpreted as a count of unique participants across conditions.
The analysis population is not reported in the registry record. It is not stated whether the summaries include all randomized participants, only participants with available measurements, or a different set. No participant-flow accounting is available in the registry record for this analysis. Without those details, the possibility that the analyzed observations differ from the intended population cannot be evaluated.
These gaps matter because outcome selection, missingness, and analysis population can affect both the apparent results and their uncertainty. The registry record does not report enough detail to assess these issues or to determine whether the posted summaries follow a prespecified statistical plan.
12. 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 |
|---|---|---|---|
| Leucine 4 Grams | 0 | 7 | 0.0% |
| Leucine 8 Grams | 0 | 8 | 0.0% |
| Leucine 0 Grams-control | 0 | 8 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Leucine 4 Grams | 0 of 7 |
| Leucine 8 Grams | 0 of 8 |
| Leucine 0 Grams-control | 0 of 8 |
The registry reports no serious adverse events for the listed arms: 0 among 7 at risk in Leucine 4 Grams, 0 among 8 at risk in Leucine 8 Grams, and 0 among 8 at risk in Leucine 0 Grams-control. These are event counts within the recorded at-risk groups. The registry also records 0 participants with other adverse events in each arm, with the same at-risk counts.
These entries describe what was reported in the registry; they do not establish that no adverse events occurred outside the recorded categories or observation period. The deaths fields are not populated with a count, so deaths are not reported in the registry record. The record does not provide event definitions, follow-up duration for safety, severity details for non-serious events, or a description of how adverse events were collected.
With limited arm-specific denominators, zero recorded events cannot be read as proof that an event is impossible or that the conditions have equivalent safety. The registry does not report a statistical comparison of adverse-event rates or uncertainty intervals. These counts should be understood as descriptive safety reporting, not as a basis for conclusions about comparative risk.
13. What the Result Does, and Does Not, Mean
The posted weight results establish that the registry contains mean and standard deviation summaries for the 4-gram, 8-gram, and 0-gram leucine conditions at a stated timeframe of 4 weeks. The reported means are 93.4, 91.7, and 91.9 kilograms, respectively. Those numbers describe the recorded values in the named arms. They do not show how much participants’ weight changed over time, because the record does not specify whether the reported values are endpoint measurements or changes from baseline.
The data do not establish that leucine supplementation changed body weight or that the doses differed from control. No inferential comparison, confidence interval, or p-value for the primary outcome is reported. The distinction is important: a difference between descriptive means is not automatically a reliable estimate of a treatment effect. The uncertainty and the analysis structure matter, particularly when the registry calls the study a crossover but describes three randomized groups.
The results also do not settle the study’s broader metabolic questions. Energy Expenditure is listed as a secondary outcome, and the description names other metabolic measures, but detailed results for those measures are not reported in the registry record for this analysis. The body-weight summaries cannot answer whether metabolism, glucose handling, insulin sensitivity, or circulating lipids changed.
The study is described as a pilot intended to inform future research. Its posted summaries can be read as limited descriptive information, but the registry does not report the statistical plan, analysis population, missing-data procedures, or a trial-level sample-size justification. These omissions constrain conclusions about precision and generalizability. The figures should not be taken as evidence for or against a clinically meaningful effect, nor as a substitute for a controlled treatment estimate with uncertainty.
14. Why This Trial Matters Statistically
This trial illustrates why design labels and outcome summaries need to be read together. The registry identifies a randomized, triple-masked crossover model, while the arm descriptions refer to three groups. In general, crossover and parallel-group designs call for different approaches to estimating treatment contrasts. Without an account of treatment order, measurement periods, and participant-level exposure, it is not possible to determine which analysis structure is appropriate for the posted summaries.
The record also illustrates the distinction between descriptive and inferential evidence. Means and standard deviations communicate the center and spread of recorded weight values. They do not by themselves show the uncertainty around a contrast or establish whether a difference is compatible with chance variation. No inferential result for the primary endpoint is reported, so the descriptive statistics should not be mistaken for a formal comparison.
The registry describes this as a pilot that could inform more definitive trials, but does not report a sample-size justification for the trial itself. Its stated planning assumptions concern illustrations based on an observed effect, and the continuous endpoint is marked as lacking an estimable two-arm comparison. This makes the distinction between a planning exercise and an observed analysis especially relevant: a planning calculation is not a result and cannot supply missing evidence about the treatment contrast.
Finally, the record shows why outcome definitions and analysis populations matter. The timeframe is stated, but the reported weight value is not identified as a change or endpoint-only measurement. The denominators are listed by arm without an explanation of how they relate to enrollment or crossover exposure. Clearer reporting of these elements would be needed to interpret the body-weight findings precisely.
15. 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 registry does not explain how the crossover designation relates to its description of participants being randomized into three groups. It does not report treatment sequence, period structure, washout, or whether participants received every condition. This prevents a clear determination of whether the outcome summaries are independent group summaries or repeated measurements from the same participants.
The primary weight outcome is reported as a mean and standard deviation at 4 weeks, but the measurement definition is incomplete. The registry does not state whether the values are follow-up measurements, changes from baseline, or another summary. Baseline values and measurement schedules are not reported in the registry record for this analysis.
There is no reported inferential analysis for the primary endpoint, and no confidence interval or p-value is available. The record also does not report the analysis population, missing-data handling, participant flow, or a prespecified statistical analysis plan. These omissions prevent assessment of how the reported denominators were formed and how uncertainty should be estimated.
The enrollment is 8, while the arm-specific outcome denominators are 7, 8, and 8. The registry does not explain their relationship, and they should not be added together or treated as a count of unique participants. Detailed results for the secondary outcome and other metabolic measures named in the study description are not reported in the registry record for this analysis. Adverse-event reporting is limited to the recorded counts; event definitions, safety follow-up, and the deaths count are not reported in the registry record.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: The Effects of Leucine on Body Weight — NCT00683826.
- Registry record last updated 2013-03-05; status last verified 2013-03.
- Results first posted 2011-08-09.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
19. Record Summary
The registry identifies NCT00683826 as a completed, randomized, triple-masked study with a crossover model, sponsored by Columbia University. Enrollment is recorded as 8, and the conditions are overweight and obesity. The primary outcome is weight in kilograms, summarized as a mean and standard deviation at 4 weeks.
Posted mean weights are 93.4 kilograms for Leucine 4 Grams, 91.7 kilograms for Leucine 8 Grams, and 91.9 kilograms for Leucine 0 Grams-control. The corresponding standard deviations are 16.8, 17.2, and 15.2, with arm-specific denominators of 7, 8, and 8. No inferential analysis of the primary outcome is reported. Energy Expenditure is listed as a secondary outcome, but detailed results are not included in the registry record for this analysis.
The registry does not report how its crossover designation relates to the arm descriptions, or provide the analysis plan, missing-data methods, or analysis population. The results therefore support descriptive reading of the posted arm summaries, but not a precise treatment-effect conclusion.