Comparison of Two Programs for Weight Loss and Impact on Metabolic Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Two Programs for Weight Loss and Impact on Metabolic Syndrome (NCT02023515), a randomized na study. The primary outcome is Weight Loss.

2. Clinical Question

The trial also addresses the broader question of whether stress management may be relevant to weight management and emotional eating. That purpose appears in the registry summary, while the primary outcome is specifically weight change. A secondary outcome is listed as decrease in stress, but a result for that outcome is not reported in the registry record.

The central statistical comparison is between participants assigned to Stress Management and those assigned to Standard Behavioral Weight Loss. The posted arm means are 1.6 kg and 3.9 kg, respectively. The reported mean difference is -2.3 kg, with the comparison expressed as Stress Management minus Standard Behavioral Weight Loss. The registry record does not explain the direction used to code weight change, so those values should be read as recorded changes rather than automatically interpreted as kilograms lost or gained.

3. Trial Design

This was a randomized, parallel-group trial with no masking. The registry record lists 49 participants as the enrollment. It lists the study as completed, with a start date of 2013-12 and primary completion in 2014-07. The study phase is recorded as NA. The registry record does not report further details about how the random sequence was generated, how assignment was concealed, or whether allocation was implemented as planned.

Participants were assigned to one of two behavioral programs. In Stress Management, participants were to undergo Emotional Brain Training during a 90-minute session once per week for ten weeks. The description characterizes this as a stress-management approach. In the Standard Behavioral Weight Loss arm, participants were to receive a standard behavioral weight loss program in 90-minute sessions once per week for 10 weeks. Both descriptions therefore specify weekly sessions over ten weeks, while the programs themselves differ.

Random assignment is intended to make comparison groups similar, on average, with respect to factors that could affect an outcome. It does not ensure that the groups are identical, particularly in a trial with limited enrollment. Because masking was none, participants and study personnel were not described as blinded to assignment. The registry record does not report whether outcome assessors were masked separately.

The primary outcome was weight change from baseline to 20 weeks, reported as a continuous measure with a mean and standard deviation. The posted arm counts are 24 for Stress Management and 25 for Standard Behavioral Weight Loss. The registry record does not describe additional follow-up schedules, treatment adherence, participant flow, or the analysis population used for the posted results.

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

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 Loss, measured over Weight change from baseline to 20 weeks.

The primary endpoint is weight change from baseline to 20 weeks, measured in kilograms. It is a continuous outcome: each participant’s change can take a range of values, and the arm-level results are summarized by a mean and standard deviation. The registry record does not report whether the change was calculated as follow-up minus baseline or baseline minus follow-up. That coding detail matters when assigning a clinical direction to positive and negative values, so the posted means should be interpreted as recorded rather than relabeled as weight loss or weight gain.

Weight is used as the primary outcome because the study concerns weight management and compares behavioral programs intended to address it. A measurement at a specified follow-up point gives a common endpoint for comparing the randomized arms. In general, a continuous endpoint retains information about the size and direction of individual changes, rather than reducing the result to a count of participants who did or did not cross a threshold. The registry record does not report a threshold for classifying a participant as having achieved a particular amount of weight change.

The posted means are 1.6 kg in Stress Management and 3.9 kg in Standard Behavioral Weight Loss. The primary comparison is the difference between these arm means at the stated time point, rather than a comparison of the programs’ full trajectories over time. Repeated measurements, intermediate time points, and additional details about endpoint measurement are not reported in the registry record.

7. Results Posted in the Registry

• Stress Management: mean 1.60 versus 3.90 on control; difference -2.30 (95% CI -4.30 to -0.30), standardized effect d = -0.65; z-test p = 0.024.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is continuous, and the registry summarizes it with a mean and standard deviation in each arm. A mean represents the average of the recorded values; a standard deviation describes how dispersed those values are around the mean. These summaries are useful for a direct comparison, but they do not show the full distribution, reveal whether values are skewed, or identify unusual observations. Such participant-level information is not reported in the registry record.

What does the mean difference represent?

The mean difference compares the arm means using a stated subtraction order: Stress Management minus Standard Behavioral Weight Loss. The reported estimate is -2.3 kg. In that ordering, a negative value means the Stress Management mean is numerically lower than the comparison-arm mean. The arm means are 1.6 kg and 3.9 kg, respectively. The registry record does not define whether positive change represents an increase or decrease in weight. Consequently, the sign of the statistical contrast can be described, but it should not be translated into a direction of weight loss without that definition.

A mean difference is expressed in the endpoint’s original units, here kilograms, which makes it interpretable on the recorded measurement scale. It is distinct from a standardized effect size, which expresses a difference relative to variability. The posted standardized effect is -0.647. Standardized effects can help compare outcomes measured on different scales, but they are less directly tied to a clinically familiar unit. Neither type of estimate alone establishes clinical importance; the registry record does not state a threshold for a meaningful weight change.

What does the interval add?

The reported interval for the mean difference runs from -4.296 to -0.304 kg. An interval estimate conveys uncertainty around a point estimate: under the method used, it describes a range of values compatible with the data and assumptions. It is not a range containing all individual participant outcomes, and it is not a guarantee that the true difference lies inside it. The confidence level and the method used to calculate the interval are not reported in the registry record, so those details cannot be inferred from the endpoints alone.

How should the p-value be read?

The unadjusted p-value is 0.024. In general, a p-value describes how unusual a test statistic at least as extreme as the observed one would be if a specified null model and its assumptions held. It does not quantify the probability that the null hypothesis is true, measure the importance of a difference, or describe the chance of success in a repeat trial. The registry record does not identify the test used or describe its assumptions. Because the value is identified as unadjusted, it should not be treated as accounting for multiple outcomes or comparisons.

Statistical significance is often assessed against a threshold chosen in advance, but the registry record does not report the trial’s original statistical plan or a prespecified threshold for interpreting this result. The planning illustration elsewhere uses a two-sided significance level of 0.05; that is a stated assumption for the planning calculation, not evidence of the original trial’s analysis plan. These are distinct uses of significance levels and should not be conflated.

Why does variability matter?

The posted standard deviations are 3.8 kg and 3.3 kg. In general, variability affects how precisely an arm mean and a difference between means can be estimated: more variation tends to make an estimate less precise when other features are held constant. The spread also matters when planning a later study, because a target difference must be distinguished from the background variability. These general principles do not reveal the individual data or justify a particular model for this trial. Whether the observed values meet assumptions of a specific statistical test is not reported in the registry record.

The comparison also has a design context. Randomization is intended to reduce systematic baseline differences between assigned groups, while parallel assignment means participants remain in their assigned group rather than crossing between programs. The registry record states randomized allocation and a parallel model, but does not describe sequence generation, concealment, adherence, or departures from assignment. No masking was used. In general, lack of masking can affect behavior, co-interventions, and outcome assessment; the available record does not establish whether any such effects occurred.

What is not specified about the analysis?

The registry lists no analysis entries. It does post arm summaries and a comparison, but does not report whether the comparison was adjusted for baseline weight or other variables, how missing follow-up values were treated, or which participants were included in the analysis. The registry record also does not report model diagnostics, sensitivity analyses, subgroup analyses, or a prespecified statistical analysis plan. These omissions limit assessment of whether the reported comparison follows a planned approach and how robust it may be to alternative analytic choices.

In general, over-dispersion matters when data are counts and their variability exceeds what a chosen count model expects; a model that ignores it can understate uncertainty. This endpoint is reported as a continuous measure with means and standard deviations, not as a count outcome, so that count-data issue is not directly indicated by the posted summaries. More broadly, the appropriate method depends on the outcome’s scale, distribution, design, and missingness. Details needed to verify those choices are not reported in the registry record.

10. Confidence Intervals and Precision

The posted mean difference is -2.3 kg, with a reported interval from -4.296 to -0.304 kg. This interval communicates uncertainty in the estimated difference, not variation among individual participants. The arm standard deviations, 3.8 kg and 3.3 kg, describe that within-arm variability instead. These measures answer different questions: the interval concerns the precision of the between-arm estimate, while the standard deviations describe how widely participant values vary around each arm mean.

The interval’s confidence level is not reported in the registry record, and the method used to calculate it is also not stated. It should therefore be quoted as the reported interval without labeling it as a particular confidence level. In general, an interval that spans a wider range indicates less precision than a narrower interval, all else being comparable. Here, the reported range includes differences from -4.296 to -0.304 kg, so it leaves uncertainty about the size of the mean difference. The registry record does not specify a threshold for deciding what range would be clinically important.

The unadjusted p-value of 0.024 gives a separate view tied to a hypothesis test; it does not replace the interval or make the estimate more precise. A p-value cannot show the range of plausible effect sizes, while an interval cannot by itself establish clinical relevance. Both should be interpreted alongside the outcome definition and design. Since the registry record does not clarify the sign convention for weight change, the numerical direction of the contrast is clearer than its practical direction as weight loss or gain.

Precision is also affected by enrollment, variability, and analysis choices. The posted arm counts are 24 and 25, and the standard deviations show variation in both groups. The record does not report missing-data handling or the exact analysis population, so the impact of incomplete follow-up on precision cannot be assessed from the posted information.

11. 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, not total event counts. They are illustrations based on the observed effect, not a report of the trial’s original design assumptions. The stated calculation assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect targeted is a stated fraction of the observed effect.

For planning at 100% of the observed effect, the illustration gives 38 participants per arm for 80% power and 51 participants per arm for 90% power. At 75% of the observed effect, it gives 67 participants per arm for 80% power and 90 participants per arm for 90% power. At 50% of the observed effect, it gives 150 participants per arm for 80% power and 201 participants per arm for 90% power.

In plain language, 80% power is the probability, under the assumed model and target effect, of detecting that effect at the chosen significance level; 90% power represents a higher probability of detection under those same assumptions. A higher power target generally requires more participants. Likewise, planning to detect a smaller effect requires more participants, as the sequence of illustrations demonstrates. These are planning scenarios rather than observed power: they do not measure how likely the completed trial was to detect its actual effect. The registry record does not report the original sample-size justification or design assumptions.

12. 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 = -2.300; pooled standard deviation σ = 3.553.
2. n = 2 × (1.96 + 0.842)² × 3.553² / -2.300² = 37.5, rounded up to 38 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 <- -2.3                      # observed difference in means
sigma <- 3.55348196035286                     # 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(2023515)
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 = 38 (80% power), 51 (90% power)
 75% of observed effect: n per arm = 67 (80% power), 90 (90% power)
 50% of observed effect: n per arm = 150 (80% power), 201 (90% power)
power.t.test: 38.5 
Simulated power at n = 38 per arm: 0.791 (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.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists weight change as the primary outcome and decrease in stress as a secondary outcome. It also records two outcome measures, while the secondary-outcome list contains one named outcome. The result posted for weight change has an unadjusted p-value of 0.024. A result for decrease in stress is not reported in the registry record.

When a study examines multiple outcomes, time points, comparisons, or subgroups, the chance of obtaining at least one apparently notable result can increase. Statistical procedures can adjust for multiple testing, or investigators can define a primary outcome and analysis in advance. The registry record does not report a multiplicity strategy, adjustment, or the original statistical analysis plan. The posted p-value should therefore be understood as unadjusted, not as evidence that multiple testing has been addressed.

Important information about missing data is also not reported. The record does not state how many participants had an observed 20-week weight measurement, whether any participants withdrew, why measurements might be missing, or how missing observations were handled. It does not identify whether the result uses all randomized participants, only participants with available outcome data, or another analysis population. The arm counts in the outcome summary should not be assumed to specify the analysis set without an explicit description.

These gaps matter because different approaches to missing observations can change both the estimate and its uncertainty, especially if missingness is related to outcomes or treatment assignment. In general, analysis populations and missing-data assumptions should be stated to clarify the meaning of an estimate. The record lists no analysis entries and does not report sensitivity analyses, so the robustness of the result to alternative missing-data assumptions cannot be evaluated.

14. 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 serious adverse event figures report zero serious adverse events among 24 participants at risk in Stress Management and zero among 25 participants at risk in Standard Behavioral Weight Loss. The other adverse event figures likewise report zero events among 24 at risk in Stress Management and zero among 25 at risk in Standard Behavioral Weight Loss. These figures describe the counts recorded in the registry; they do not establish that no events occurred outside the registry’s reporting definitions or observation period.

The registry record does not report the event definitions, the period during which events were collected, how actively events were sought, or whether all participants contributed safety information for the same duration. It also does not list serious-event terms. Death counts are not reported in the registry record. Zero recorded events should not be read as proof that a program has no risk, and the figures alone do not support a detailed comparison of safety between arms.

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

The posted results show different mean recorded weight changes at 20 weeks: 1.6 kg in Stress Management and 3.9 kg in Standard Behavioral Weight Loss. The estimated difference, defined as Stress Management minus Standard Behavioral Weight Loss, is -2.3 kg. The reported interval is -4.296 to -0.304 kg, and the unadjusted p-value is 0.024. These statistics describe the comparison in this completed randomized trial.

They do not establish the direction of weight loss or gain, because the registry record does not define the sign convention used for weight change. They also do not establish whether the observed difference is clinically important; no threshold for meaningful change is reported. A statistically notable comparison is not the same as evidence of a particular clinical benefit, and the interval leaves uncertainty about the size of the difference.

The results do not show whether stress decreased, despite decrease in stress being listed as a secondary outcome. They do not establish how stress and weight change were related, what happened at intermediate time points, or how adherence to the programs affected outcomes. Those results and details are not reported in the registry record. The posted weight comparison also does not show results for subgroups or for people outside the enrolled population.

Random assignment supports a comparison of assigned groups, but the registry record does not provide enough information to assess the full analysis process, including missing-data handling, analysis population, or adjustment choices. With enrollment of 49, the result should be read as an estimate with uncertainty rather than as a definitive characterization of the programs. It is a report of the observed endpoint comparison, not a guarantee of the result that another trial or a different population would produce.

16. Why This Trial Matters Statistically

This trial illustrates why the outcome definition matters as much as the numerical contrast. The primary endpoint is weight change, but the registry record does not state whether positive values indicate an increase or a decrease in weight. The arm means and their difference can be reported precisely as recorded, yet their clinical direction cannot safely be translated into weight loss or gain without that coding information. Clear endpoint conventions are essential for interpreting signs and communicating comparisons.

It also illustrates the difference between a point estimate and its precision. The mean difference is -2.3 kg, while the reported interval ranges from -4.296 to -0.304 kg. The point estimate alone conceals the uncertainty around its magnitude. The arm standard deviations describe participant-level spread, which is different from uncertainty in the estimated difference. Keeping those quantities conceptually separate helps avoid treating a mean as representative of every participant.

The record offers a useful example of the limits of a p-value when the analysis plan and multiplicity handling are not described. The unadjusted p-value is 0.024, but the record does not report the test, any adjustment for multiple outcomes, or the original analysis plan. A p-value is one component of evidence, not a measure of effect size or clinical importance. Interpreting it alongside the estimate, interval, design, and reporting gaps gives a more complete statistical reading.

Finally, the planning illustrations make explicit that study size depends on the effect a future study aims to detect. Smaller target effects require more participants under the stated assumptions. Those projections are not observed power and do not reveal the original rationale for enrollment. The distinction between a retrospective result and a prospective planning scenario is important when using trial findings to inform future research.

17. 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 record gives limited information about the population beyond metabolic syndrome. Eligibility criteria, participant characteristics, recruitment setting, and baseline balance are not reported. This makes it difficult to judge how closely the enrolled participants resemble other groups or how broadly the results might apply. The enrollment was 49, and the record does not describe participant flow or retention.

The meaning of the primary endpoint has an important unresolved detail: the direction used to calculate weight change is not defined. The outcome is described as change from baseline to 20 weeks, but the record does not state whether values represent follow-up minus baseline or the reverse. This limits interpretation of whether the reported means correspond to weight loss or gain. Further measurement details, including assessment procedures and intermediate measurements, are not reported.

The trial was unmasked. The registry record does not report whether outcome assessors were masked or whether expectations, adherence, co-interventions, or treatment fidelity were assessed. It also does not report the randomization sequence method or allocation concealment. These details are relevant to understanding the conduct of a behavioral intervention comparison, but their absence does not show that a particular bias occurred.

Analysis information is sparse. The record lists no analysis entries and does not describe the statistical test, adjustment for baseline values, analysis population, handling of missing data, or sensitivity analyses. The confidence level and calculation method for the reported interval are not stated. Multiplicity handling is also not reported. A decrease-in-stress result is not reported in the registry record, limiting assessment of the study’s secondary question.

Finally, the safety summary has no reported event definitions or observation window, and deaths are not reported in the registry record. These reporting gaps constrain interpretation of both effectiveness-related outcomes and safety. They should be treated as unknowns in the registry record, not as evidence that the underlying procedures were absent.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Comparison of Two Programs for Weight Loss and Impact on Metabolic Syndrome — NCT02023515.
• Registry record last updated 2017-06-27; status last verified 2017-05.
• Results first posted 2017-06-27.
• 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.

21. Record Summary

NCT02023515 is a completed, randomized, parallel-group study with no masking. It enrolled 49 participants and compared Stress Management using Emotional Brain Training with Standard Behavioral Weight Loss. The registry lists metabolic syndrome as the condition and weight change from baseline to 20 weeks as the primary outcome, measured in kilograms.

The posted means are 1.6 kg for Stress Management and 3.9 kg for Standard Behavioral Weight Loss. The mean difference, Stress Management minus Standard Behavioral Weight Loss, is -2.3 kg, with a reported interval from -4.296 to -0.304 kg and an unadjusted p-value of 0.024. The sign convention for weight change is not reported in the registry record.

Decrease in stress is listed as a secondary outcome, but its result is not reported in the registry record. The record also does not report the original sample-size rationale, analysis population, missing-data methods, or multiplicity plan.