Comparative Effects of 2 Diets in Veterans With the Metabolic Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparative Effects of 2 Diets in Veterans With the Metabolic Syndrome (NCT00852475), a randomized na study. The primary outcome is Weight Changes in Veterans With MetS..

2. Clinical Question

The registry describes a study of two commonly used dietary approaches alongside the MOVE! program. Its stated aims included examining cardiometabolic risk factors, including lipid measures, inflammatory markers, endothelial function, and post-meal lipid responses. The posted primary outcome is narrower: mean weight change at six months. The displayed comparison therefore addresses the difference in that outcome between the two assigned programs, rather than answering every broader question in the study description.

The registry record identifies 46 participants as enrolled. For the primary result, it reports outcome sample sizes of 23 in the MUFA arm and 16 in the PUFA arm. Why those outcome counts differ from the overall enrollment is not reported in the registry record. No additional population characteristics or eligibility criteria should be inferred from the stated condition and participant group alone.

3. Trial Design

The registry identifies this as a randomized, parallel-group trial with no masking. Participants were assigned to one of two diet programs: MUFA MOVE!, based on a monounsaturated-fat-enriched diet, or PUFA MOVE!, based on a polyunsaturated-fat-enriched diet. Both arm descriptions include exercise and identify the program as part of MOVE! The sponsor was the VA Office of Research and Development.

The study is marked completed. Its recorded start was 2010-02, and its primary completion was 2014-12. The registry reports enrollment of 46. For the primary outcome, the arm-level sample sizes are 23 for MUFA and 16 for PUFA. The reasons that the outcome counts do not match the enrollment figure are not reported in the registry record, nor does the record identify the population used for the analysis.

The primary outcome was weight change in kilograms, assessed at six months from baseline. The posted arm summaries are means with standard errors. The registry also posts one secondary outcome, change from baseline in endothelium-dependent flow-mediated dilation assessed by the brachial artery reactivity test at rest, at the same six-month timeframe. Although the study description discusses additional cardiometabolic measurements, detailed results for those measures are not posted as outcomes in the record.

The registry does not report the original sample-size justification, allocation procedures beyond randomization, or further operational details of the trial design. The phase is listed as NA. These omissions limit how fully the design can be reconstructed from 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

Reasons for not completing this period:

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.

6. Primary Endpoint

The registry lists the primary outcome as Weight Changes in Veterans With MetS., measured over 6 months from Baseline.

The primary endpoint is weight change in kilograms at six months from baseline. The registry reports the mean change in each arm and gives the dispersion as a standard error. A negative mean change represents a decrease from baseline in the measured weight; the posted means are -2.3 kg in the MUFA arm and -6.2 kg in the PUFA arm.

Weight is a direct, continuous measure that permits a comparison of average change between the randomized groups. The study description places weight within a broader investigation of cardiometabolic risk factors in veterans with metabolic syndrome. The registry does not provide further detail about how weight was measured, how the endpoint was defined for individual participants, or whether the primary analysis adjusted for other variables.

The comparison estimate is a mean difference of -3.9 kg for PUFA relative to MUFA, with a 95% confidence interval from -6.949 to -0.851 kg. This estimate expresses the observed separation in group means, while the interval conveys uncertainty about the difference under the analysis used. It is a group-level comparison and does not describe the range of individual changes. It also does not, by itself, answer the broader questions about the other cardiometabolic measures named in the study description.

7. Results Posted in the Registry

• PUFA: mean -6.20 versus -2.30 on control; difference -3.90 (95% CI -6.95 to -0.85), standardized effect d = -0.82; z-test p = 0.012.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Endothelium-dependent FMD Assessed by the Brachial Artery Reactivity Test (BART) at Rest .

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • PUFA Arm: mean 1.50 versus 0.19 on control; difference 1.31 (95% CI 0.37 to 2.25), standardized effect d = 0.91; z-test p = 0.006.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for PUFA Arm than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The registry posts one secondary outcome: change from baseline in endothelium-dependent flow-mediated dilation, assessed at rest by the brachial artery reactivity test. The secondary comparison points in the same broad between-arm direction as the primary result: the PUFA arm has a higher posted change in this measure, alongside a more negative weight-change mean. These are distinct measurements, and a shared direction does not make them interchangeable or establish a common mechanism.

The secondary outcome adds a physiological measure to the weight comparison. The study description also names other planned areas of interest, including lipids, inflammatory markers, post-meal lipid responses, postheparin lipases, transfer protein activity, visceral adipose tissue, and insulin resistance. The registry record does not post outcome results for those measures in the listed secondary results. Their absence from the posted outcomes should not be interpreted as evidence that they were measured or that they had any particular result.

The secondary comparison has an unadjusted p-value and confidence interval in the registry. Unadjusted secondary findings carry less weight when the complete number of outcomes and analyses is not clear, because repeated testing can increase the chance of an apparently unusual result. The registry lists two outcome measures overall, one posted secondary outcome, and no reported analyses in its analysis listing. It does not state whether this secondary endpoint was designated in advance, how many other analyses were conducted, or whether any multiplicity strategy was used.

For that reason, the secondary result is best treated as additional, exploratory context rather than as independent confirmation of the primary finding. It may be relevant to the study's broader physiological aims, but incomplete reporting makes it difficult to judge its place in the full analysis plan. The registry record does not establish that changes in weight and flow-mediated dilation are causally linked or that either measure accounts for the other.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Endothelium-dependent FMD Assessed by the Brachial Artery Reactivity Test (BART) at Rest .

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous, and the registry reports a mean for each arm. The comparison is a difference in means, expressed as the PUFA mean minus the MUFA mean. The reported estimate is -3.9 kg, so the sign indicates that the PUFA mean is lower than the MUFA mean for weight change. Because both group means are negative, each represents a decrease from baseline on average. The comparison is about the difference between those averages, not about how many individual participants lost weight.

What does the standard error describe?

The standard error describes the uncertainty in an estimated mean, rather than the spread of individual observations. A smaller standard error generally indicates a more precisely estimated mean, all else being equal. The registry reports standard errors of 0.99 kg for MUFA and 1.2 kg for PUFA. These quantities should not be interpreted as the range of participant-level weight changes. The registry does not report the raw observations or additional distribution summaries that would describe individual variability.

How should the mean difference be read?

A difference in means expresses the separation between the two group averages on the original measurement scale. Here, the scale is kilograms and the comparison is oriented as PUFA relative to MUFA. A negative estimate indicates a lower mean change in PUFA than MUFA. The estimate is a summary of the observed groups, and the confidence interval provides information about its uncertainty. Neither statistic describes the response of every participant or proves that the same contrast would occur in another population.

Random allocation is intended, in general, to make treatment groups comparable on average with respect to factors that could affect the outcome. It does not guarantee that the groups are identical in a particular trial, especially with a modest enrollment. The registry identifies the allocation as randomized but does not report the specific randomization procedure or whether the primary comparison adjusted for baseline characteristics. No such details should be assumed.

What does the p-value contribute?

The registry posts an unadjusted p-value of 0.012 for the primary comparison. In general, a p-value describes how compatible the data are with a specified null model, conditional on the model and its assumptions. A smaller p-value indicates that the observed data would be less expected under that model. It is not a measure of the size of the difference, the probability that a null hypothesis is true, or the probability that the result will recur.

“Unadjusted” indicates that the displayed value has not been adjusted for multiple comparisons. This matters when many outcomes or analyses are examined, because the chance of finding at least one small p-value can increase with the number of comparisons. The registry record does not report a multiplicity procedure, and the full number of analyses conducted is not documented. The p-value should therefore be read as the unadjusted statistic reported for this comparison, not as evidence that all possible sources of statistical uncertainty have been addressed.

Why does a confidence interval matter?

A confidence interval gives a range of estimates compatible with the observed data under a specified statistical procedure. In general, the interval reflects both the estimated effect and its precision. A narrow interval indicates greater precision than a wide interval on the same scale, while an interval that spans zero leaves uncertainty about the direction of the difference. The primary interval is entirely negative, but its breadth also shows that the exact size of the difference is not pinned down. The interval does not include uncertainty from unreported design or analysis choices.

The registry reports a standard-error-based description for the arm summaries and a confidence interval for the between-arm estimate. The record does not state the model, degrees of freedom, or other details of the inferential calculation. The interval and p-value can be described as posted, but the exact analysis procedure cannot be reconstructed from the available information.

What can be learned from the secondary result?

The secondary endpoint is a continuous measure of change from baseline in flow-mediated dilation, expressed as a percentage of change and assessed by the brachial artery reactivity test at rest. The registry reports arm means and standard errors, along with a mean difference and an unadjusted p-value. In general, a secondary measure can add context about a different aspect of the study question, but its interpretation depends on the outcome's measurement, analysis, and place in the original plan. Those details are not fully reported for this trial.

The posted arm-level sample sizes differ between groups and are smaller than the overall enrollment. Statistical precision depends in part on the amount of information available, and unequal group counts can affect precision. The registry does not explain why the outcome counts differ from enrollment, whether missing outcomes occurred, or how any missing data were treated. It also does not report whether the analyses followed an intention-to-treat principle or another analysis population.

General statistical interpretation should keep the trial design, endpoint definition, estimate, uncertainty, and reporting limitations in view at the same time. The posted result quantifies one randomized between-group contrast at one timeframe. It does not supply the absent analysis details, replace the need to consider outcome multiplicity, or establish that a similar estimate would be observed elsewhere.

11. Confidence Intervals and Precision

The primary mean difference is -3.9 kg, with a 95% confidence interval from -6.949 to -0.851 kg. The interval is entirely on the negative side of zero, consistent with a lower mean weight change in the PUFA arm than in the MUFA arm under the direction used for the comparison. The interval is not concentrated at a single value: it allows a range of possible differences, so the exact magnitude remains uncertain.

In general, a confidence interval describes uncertainty in an estimate under the statistical method used. It is not a range expected to contain most individual participants' outcomes, and it does not represent every source of uncertainty about the study. In this case, the registry does not provide enough detail to assess the analysis population, missing-data handling, or the specific inferential procedure behind the interval. Those issues are relevant when judging how broadly the interval can be interpreted.

The secondary mean difference is 1.31 percentage points, with a confidence interval from 0.373 to 2.247, in the registry's percentage-of-change scale. This is also an interval that excludes zero under the posted calculation, but the secondary analysis is unadjusted and should be interpreted with the other limitations on secondary outcomes in mind.

Precision is not the same as importance. An interval can help show which effect sizes are compatible with the data, but the registry does not report a threshold for a clinically meaningful difference. The reported intervals also do not resolve uncertainty arising from the limited outcome counts or incomplete reporting of design and analysis details.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for this continuous-outcome illustration, not total events. They estimate the group size that would be needed under the stated planning assumptions for different fractions of the observed effect. The assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect.

The 80% power column gives the illustrated participants per arm for a design with an 80% chance of detecting the selected effect under those assumptions, if that effect and the statistical model were correct. The 90% column gives the corresponding per-arm planning count for a 90% chance. These are prospective planning quantities; they are not estimates of the probability that this completed trial detected its effect.

The planning rows use the full observed effect, 75% of the observed effect, and 50% of the observed effect. As the effect selected for planning becomes smaller, more participants are needed to detect it at the same power and significance level. For example, the planning display gives 24 participants per arm for 80% power when using 100% of the observed primary effect, and 94 per arm when using 50%. The corresponding 90% figures are 32 and 126 per arm.

These are illustrations computed from the observed effect, not the original trial's sample-size plan. The trial's own design assumptions and sample-size justification are not reported in the registry record. This is not observed power: observed power is not a substitute for interpreting the estimate and its confidence interval, and these planning values do not describe the probability that the trial's result is correct.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -3.900; pooled standard deviation σ = 4.769.
2. n = 2 × (1.96 + 0.842)² × 4.769² / -3.900² = 23.5, rounded up to 24 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -3.9                      # observed difference in means
sigma <- 4.76907436199838                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(852475)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 24 (80% power), 32 (90% power)
 75% of observed effect: n per arm = 42 (80% power), 56 (90% power)
 50% of observed effect: n per arm = 94 (80% power), 126 (90% power)
power.t.test: 24.5 
Simulated power at n = 24 per arm: 0.795 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry reports an unadjusted primary p-value and an unadjusted secondary p-value. It does not report a method for controlling multiplicity, such as a prespecified hierarchy or a correction across outcomes. The record lists two outcome measures and one posted secondary outcome, while its analyses listing contains no reported analyses. It is therefore not possible to determine from the registry how many comparisons were made or whether the posted outcomes represent the complete set examined.

In general, multiplicity matters because testing several outcomes can increase the chance of at least one result appearing statistically unusual even when no underlying difference exists. A multiplicity plan can define which outcome is primary and how secondary tests should be interpreted. The registry does identify weight change as the primary outcome, but it does not report the detailed analysis plan, the prespecified status of the secondary outcome, or any adjustment procedure. The posted p-values should be read as unadjusted statistics, not as multiplicity-controlled evidence.

Missing-data reporting is also limited. The registry gives overall enrollment of 46 and primary outcome group counts of 23 and 16; the reasons for the difference are not reported in the registry record. It does not describe the number or pattern of missing outcomes, how missing observations were handled, or whether imputation or another method was used. The analysis population is not reported in the registry record. It is therefore not possible to say whether the estimates include all randomized participants or to assess the consequences of any missing data.

The record also does not report whether the analysis followed an intention-to-treat principle, whether adherence was considered, or whether adjusted analyses were conducted. These are not details that can be inferred from randomization or from the arm summaries. In general, the analysis population and handling of missing observations can affect the interpretation of a randomized comparison, especially when outcome counts do not match enrollment.

These gaps do not alter the values posted for the arm means, contrasts, confidence intervals, and unadjusted p-values. They do limit how confidently the analysis process can be evaluated and how those statistics should be generalized beyond the reported comparison.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry records zero serious adverse events among the 23 participants at risk in the MUFA group and among the 16 participants at risk in the PUFA group. It also records zero other adverse events in the listed at-risk groups. These counts describe the safety information posted for the groups; they do not by themselves establish that no adverse events occurred outside the recorded categories or observation period.

Deaths are not reported in the registry record. The record does not provide serious-adverse-event terms, and no serious-event terms are listed. The timeframe and method used to collect adverse-event information are not described in the posted safety results. Without those details, the counts cannot be used to assess event ascertainment or to compare risks beyond the specific figures recorded.

Zero events in the posted groups is a count, not proof that the risk is zero. The sample sizes are limited, and uncommon events may not be observed in a trial of this size. These safety figures should be read as descriptive reporting for the registered groups, not as a guarantee about outcomes for individuals or other populations.

16. What the Result Does, and Does Not, Mean

The primary result describes a difference in average weight change between two randomized diet-and-exercise programs in veterans with metabolic syndrome at six months from baseline. The posted mean change was negative in both arms, and the estimated difference was negative for PUFA relative to MUFA. The confidence interval and unadjusted p-value quantify aspects of uncertainty under the posted analysis, while the registry's missing analysis details limit a fuller appraisal.

The result does not establish that every participant experienced the group-average change, or that an individual will have a similar response. A mean can conceal substantial variation in individual outcomes, and the registry does not post the underlying distribution. Nor does the comparison isolate diet from exercise: both program descriptions include exercise. It is a comparison of the assigned programs as described, rather than a separate test of the fatty-acid composition alone.

The result also does not answer every question in the study summary. The trial description names multiple cardiometabolic factors, but the listed posted results include weight change and one secondary flow-mediated dilation measure. No conclusion about unposted lipid, inflammatory, post-meal, or mechanistic outcomes can be drawn from the weight estimate.

Statistical evidence about a difference is not identical to evidence about clinical importance. The registry does not give a threshold for a clinically meaningful change in weight, and statistical significance does not establish that an observed contrast is important to participants. Likewise, the posted result does not establish a mechanism, long-term durability, or applicability to people other than the studied group.

The record's incomplete information about outcome counts, missing data, analysis population, multiplicity, and original sample-size planning further constrains interpretation. The appropriate reading is a reported six-month between-arm difference with an interval that excludes zero under the posted calculation, alongside uncertainties about the full analysis and the broader study aims.

17. Why This Trial Matters Statistically

This trial illustrates why statistical interpretation should distinguish an arm mean from a between-arm contrast. Both posted group means are negative, but the study question concerns how the average changes differ between randomized programs. The mean difference places that contrast on the original kilogram scale, while the confidence interval conveys uncertainty about its magnitude. Reading the estimate and interval together is more informative than treating a p-value as a complete summary.

The record also demonstrates how endpoint-specific conclusions should remain. The study summary describes a broad cardiometabolic research program, whereas the primary posted result is weight change at six months. One secondary physiological outcome is posted, but the broader set of measures named in the summary is not reported as a set of outcome results. A result for one endpoint cannot substitute for results on other endpoints.

Trial reporting is part of statistical interpretation. Enrollment is reported as 46, while the primary outcome counts are 23 and 16. The registry does not explain the counts, describe missing-data handling, identify the analysis population, or state the multiplicity approach. Those omissions do not erase the estimate, but they leave important questions about the analysis unanswered.

Finally, the sample-size illustration shows how planning depends on the effect chosen for detection: smaller target effects require more participants for the same stated power under the listed assumptions. Because these planning calculations use the observed effect and are not the original design rationale, they should not be used to infer the trial's prospective power. Together, these features make the record a useful example of separating reported findings, planning illustrations, and unreported design details.

18. 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 posted primary outcome counts are 23 in the MUFA arm and 16 in the PUFA arm, while total enrollment is 46. The registry does not explain this difference, identify the analysis population, or describe missing outcome data. This leaves uncertainty about how the reported comparison relates to all randomized participants.

The registry does not report the original sample-size justification, randomization procedure, primary analysis method, or whether covariate adjustment was used. It also does not describe how multiplicity was addressed. These omissions limit assessment of the analysis plan and the context for the unadjusted p-values. The planning illustration based on the observed effect cannot fill that gap because it is not the original design rationale.

The intervention contrast is between two programs that both include exercise, so the reported comparison cannot isolate the diet component. The study is open-label, and the registry does not provide additional details about implementation, adherence, or outcome measurement procedures. Those details should not be inferred.

The posted record includes a six-month primary endpoint and one secondary outcome, but the study description names a wider range of cardiometabolic measures. Detailed results for the other named measures are not reported in the registry record. Long-term outcomes beyond the stated timeframe are not reported in the registry record either.

The participant group is described as veterans with metabolic syndrome, but further demographic and eligibility characteristics are not reported in the registry record. Generalizability to other populations cannot be evaluated from the posted description alone. The safety record lists zero serious and other adverse events in the at-risk groups, but deaths are not reported and the event-collection timeframe is not described.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Comparative Effects of 2 Diets in Veterans With the Metabolic Syndrome — NCT00852475.
• Registry record last updated 2017-02-02; status last verified 2016-12.
• Results first posted 2017-02-02.
• 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.

22. Record Summary

NCT00852475 is a completed, randomized, open-label, parallel-group study sponsored by the VA Office of Research and Development. It enrolled 46 veterans with metabolic syndrome and compared MUFA MOVE! with PUFA MOVE!, two diet programs described as including exercise through MOVE!

The primary outcome was mean weight change in kilograms at six months from baseline. The registry reports arm means of -2.3 kg for MUFA and -6.2 kg for PUFA, with a mean difference of -3.9 kg for PUFA relative to MUFA. The 95% confidence interval is -6.949 to -0.851 kg, and the unadjusted p-value is 0.012.

One secondary outcome, flow-mediated dilation assessed at rest, is posted. The registry does not report the original sample-size justification, analysis population, missing-data approach, or multiplicity method. Outcome counts differ from total enrollment, and the reason is not reported in the registry record. Safety listings record zero serious and other adverse events in the at-risk groups; deaths are not reported in the registry record.