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 Anti-Obesity Phentermine-Topiramate Extended Release Pharmacotherapy vs Placebo Among Patients Using a Wearable Activity Tracker (NCT04408586), a randomized phase 4 study. The primary outcome is Body Weight Change.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04408586 |
| Phase | Phase 4 |
| Condition | Obesity |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 80 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Mayo Clinic |
| Results posted | Yes |
2. Clinical Question
Population
The registry describes participants with obesity enrolled in a trial that included 80 people. Participants were provided with a wearable activity tracker, digital wellness devices and lifestyle recommendations. Further eligibility details and the characteristics of the analyzed population are not reported in the registry record.
Intervention
The intervention of interest was phentermine-topiramate extended release. An online support system is also listed among the trial interventions. The registry summary describes the tracker, digital wellness devices and lifestyle recommendations as part of the study context; detailed information on how these components were delivered is not reported in the registry record.
Comparator
The comparator was placebo. The randomized groups are identified as the phentermine-topiramate extended release group and the placebo group. The registry record does not give further details about the placebo or the specific procedures used to maintain masking.
Primary question
The primary outcome asks how body weight changed, in kilograms, from baseline to 3 months in each group. The posted results give a mean change and a 95% confidence interval for each group. They do not provide a direct between-group estimate or an associated statistical test for this primary outcome, so the posted figures describe each group separately rather than quantify the randomized contrast.
3. Trial Design
This was a Phase 4, randomized, double-masked, parallel-group trial sponsored by Mayo Clinic. The registry lists an enrollment of 80 participants and a completed study. The recorded start date is 2020-06-03, and the primary completion date is 2022-06-13. Participants were assigned to phentermine-topiramate extended release or placebo; the posted outcome groups include 42 participants in the former group and 38 in the placebo group.
The registry summary places the medication comparison in a setting where participants used a wearable activity tracker and had digital wellness devices and lifestyle recommendations. An online support system is also listed as an intervention. The arm descriptions themselves are blank, so the record does not explain in detail how these elements were applied in each group, or whether their use differed by group. Dosage, treatment duration, adherence procedures and the precise masking procedures are not reported in the registry record.
The primary outcome is body-weight change in kilograms at baseline and 3 months. The registry also lists secondary outcomes concerning weight, activity, tracker use and health-related quality of life. Quantitative secondary summaries are posted for exercise sessions and tracker usage, each with a 12-month timeframe. The record does not describe a statistical analysis plan, analysis populations, participant flow, or the handling of missing outcome measurements. Those omissions limit how fully the design and the relationship between the randomized assignment and the reported outcome summaries can be evaluated.
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 | Phentermine - Topiramate Extended Release Group | Placebo Group |
|---|---|---|
| STARTED | 42 | 38 |
| COMPLETED | 42 | 38 |
| NOT COMPLETED | 0 | 0 |
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 | Phentermine - Topiramate Extended Release Group | Placebo Group | Total |
|---|---|---|---|---|
| Participants analysed | 42 | 38 | 80 | |
| Age, Continuous | years | 43.4 (SD 10.9) | 40.8 (SD 10.2) | 42 (SD 10.4) |
| Sex: Female, Male: Female | Participants | 36 | 32 | 68 |
| Sex: Female, Male: Male | Participants | 6 | 6 | 12 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| 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 | 0 | 1 | 1 |
| Race (NIH/OMB): White | Participants | 42 | 37 | 79 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 42 | 38 | 80 |
6. Primary Endpoint
The registry lists the primary outcome as Body Weight Change, measured over baseline, 3 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | kilograms |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change in body weight, measured in kilograms, from baseline to 3 months. Change scores describe how a measure shifts from a starting point, rather than reporting only the value at follow-up. This can help readers understand the amount and direction of weight change during the stated period. Negative mean changes in the posted results represent decreases in weight.
The registry reports a mean change of -10.8 kilograms in the phentermine-topiramate extended release group, with a 95% confidence interval from -13.72 to -7.92. In the placebo group, the mean change was -4.04 kilograms, with a 95% confidence interval from -7.05 to -1.04. These are separate group estimates. The registry record does not report the difference between groups, a confidence interval for that difference, or a statistical test for the primary outcome. Therefore, the group summaries alone do not provide the precision of the randomized treatment contrast.
In general, a change endpoint can focus attention on movement over time, while a confidence interval communicates uncertainty around the estimated group mean. The endpoint’s usefulness for comparing randomized groups depends on a direct between-group analysis and on clear reporting of the participants and data included. Those details are not reported for the primary comparison in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary results show mean body-weight decreases in both groups over the baseline-to-3-month timeframe. The mean change was -10.8 kilograms in the phentermine-topiramate extended release group and -4.04 kilograms in the placebo group. Each estimate is accompanied by a 95% confidence interval: -13.72 to -7.92 for the medication group and -7.05 to -1.04 for placebo. These intervals describe uncertainty around the group means, not around the difference between groups.
The randomized question concerns how outcomes compare between assigned groups. The registry record does not post a primary between-group estimate, confidence interval for the contrast, or test result. It is therefore not possible to use these posted primary statistics to quantify the size or precision of the treatment contrast, or to establish whether that contrast meets a statistical threshold. Comparing the two separate confidence intervals is not a substitute for an analysis of the difference. The result should be read as a pair of group summaries, not as a reported estimate of the randomized effect.
The quantitative secondary summaries address exercise sessions per week and tracker usage in minutes per week at 12 months. Their recalculated contrasts are unadjusted and should be treated as exploratory descriptions, not as confirmatory findings. No sponsor-reported analyses are listed for these outcomes. A lack of a small unadjusted p-value would not establish that groups are equivalent, just as a nominally notable result would not by itself establish a reliable effect. Multiple secondary outcomes are listed, and the registry record does not report whether or how multiplicity was addressed.
The posted group sizes for the primary outcome are 42 and 38. The registry does not explain whether these are all randomized participants, all participants with a measured outcome, or another analysis population. Nor does it report missingness or the methods used to handle it. Consequently, the degree to which the posted estimates preserve the benefits of randomization cannot be fully assessed from the record.
In general, interpretation is strongest when the endpoint definition, analysis population, between-group estimate, uncertainty interval and analysis method are all available. For this trial, the arm-level primary estimates provide useful descriptive information, but the absent primary contrast and analysis details leave important uncertainty about the comparative result.
9. Statistical Methods Explained
The registry reports the primary outcome as a mean, with dispersion expressed as a 95% confidence interval. The two posted group means are -10.8 and -4.04 kilograms. A mean is the arithmetic average of observed measurements in the relevant group, while a confidence interval expresses uncertainty about the estimated mean under the assumptions of the method used. In general, a confidence interval is not a range containing every participant’s result, and it is not a guarantee that the underlying value lies in that interval. The registry does not describe the procedure used to calculate the primary confidence intervals.
The primary outcome is a continuous measure. For a randomized comparison, a direct estimate of the difference in mean change between groups would ordinarily express the contrast of interest, with its own uncertainty interval and, where applicable, test result. The registry record does not report those comparative statistics for body-weight change. The separate confidence intervals around the group means cannot be treated as the confidence interval for the between-group difference. The posted primary results therefore support description of the group means, but do not show how precisely the groups differ.
For the two secondary outcomes with quantitative summaries, the posted group means and standard deviations are accompanied by recalculated, unadjusted mean differences, confidence intervals and p-values. These calculations are simple unadjusted comparisons based on the posted summary statistics; they are not reported sponsor analyses. An unadjusted comparison does not account for potential adjustment variables or the fact that several outcomes may be examined. No reported analyses are listed for these outcomes. The interpretation of their calculated comparisons should consequently remain descriptive and exploratory.
In general, a standard deviation describes variation among individual observations, whereas a confidence interval describes uncertainty around an estimated quantity. These measures answer different questions. A wide standard deviation can reflect substantial participant-to-participant variation even when the estimated mean is relatively precise; conversely, a mean difference’s confidence interval depends on the variability and the amount of information available. The 12-month secondary summaries provide standard deviations, while the primary outcome is posted with confidence intervals around the group means.
The secondary comparisons also include planning illustrations based on the observed effect. The stated assumptions are a two-sided significance level of 0.05, equal allocation between groups and a normal approximation; the planning effect is a stated fraction of the observed effect. Such illustrations indicate the per-arm sample sizes associated with those assumptions and effect scenarios. They are not observed power, do not show the power of the completed trial, and are not evidence that the original trial was designed using those assumptions. The registry does not report the trial’s sample-size justification.
In general, planning calculations based on an observed effect should be interpreted cautiously. The observed estimate can be unstable, particularly when the sample is limited, and a planning illustration does not establish that a future study will produce the assumed effect. Considering smaller fractions of an observed effect is one way to explore how planning requirements depend on the target effect, but it does not solve uncertainty about the true effect or replace a prespecified design rationale.
What does over-dispersion mean?
Over-dispersion is a general issue for outcomes whose variability is greater than a chosen statistical model expects. If a model underestimates variability, its uncertainty intervals may be too narrow and its tests may be too optimistic. This concept is relevant in general to count or event outcomes, but the primary outcome in this trial is continuous, and the registry does not report an over-dispersion model or analysis. There is no basis in the record to say that over-dispersion affected the posted primary result.
What analysis details are missing?
The registry record does not report the primary comparison method, the analysis population, covariate adjustment, treatment of repeated measurements, missing-data procedures or a prespecified statistical analysis plan. It also does not report sponsor analyses for the posted secondary summaries. Without those details, readers cannot determine whether the posted estimates were adjusted, how participants with incomplete measurements were handled, or whether the approach was specified before results were examined. These gaps are distinct from the numerical uncertainty conveyed by a confidence interval: an interval cannot account for biases introduced by an unclear analysis population or undocumented data handling.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary outcome and multiple secondary outcomes, but it does not report a multiplicity plan. Multiplicity arises when several outcomes or statistical tests are considered: even when each test uses a conventional threshold, the chance of at least one apparently notable result can increase across a collection of tests. In general, prespecifying a hierarchy, adjusting thresholds, or clearly labeling secondary analyses as exploratory can help readers understand the evidential status of findings. The registry record does not report whether any such approach was used.
The secondary comparisons described in the posted quantitative summaries are unadjusted recalculations, and the registry lists no sponsor-reported analyses for them. Their p-values should therefore not be read as multiplicity-adjusted evidence. The primary outcome has group means and confidence intervals but no reported between-group test or contrast, so the record does not support a primary significance statement either.
Missing-data methods and analysis populations are also not reported in the registry record. It is unclear whether the outcome summaries include all randomized participants, only those with observed measurements, or a defined subset. The record does not state how unavailable measurements were handled, whether participants were analyzed according to assigned group, or how any departures from the randomized assignment were treated. These details matter because incomplete outcomes can affect both the representativeness and precision of an estimate.
In general, randomization supports a fair comparison when the analysis retains the assigned groups and outcome availability is handled appropriately. That principle does not establish that these procedures were followed in any particular way. With the relevant information unreported, readers should avoid assuming either that missing data were absent or that a particular imputation or sensitivity analysis was performed.
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 |
|---|---|---|---|
| Phentermine - Topiramate Extended Release Group | 0 | 42 | 0.0% |
| Placebo Group | 0 | 38 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Phentermine - Topiramate Extended Release Group | 0 of 42 |
| Placebo Group | 0 of 38 |
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 |
|---|---|
| Phentermine - Topiramate Extended Release Group | 11 of 42 |
| Placebo Group | 3 of 38 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Phentermine - Topiramate Extended Release Group | Placebo Group |
|---|---|---|---|
| Paresthesia | Nervous system disorders | 6 of 42 | 1 of 38 |
| Dry mouth | Gastrointestinal disorders | 3 of 42 | 2 of 38 |
| Dysgeusia | Nervous system disorders | 3 of 42 | 0 of 38 |
| Insomnia | Psychiatric disorders | 3 of 42 | 0 of 38 |
| Headache | Nervous system disorders | 2 of 42 | 0 of 38 |
The registry reports zero serious adverse events in the phentermine-topiramate extended release group among 42 participants at risk and zero in the placebo group among 38 participants at risk. It also reports zero deaths in both groups. These are the posted serious-event and death counts for the recorded groups.
Zero recorded serious adverse events does not mean that serious events are impossible, nor does it establish that the groups have identical safety profiles. The counts describe what was recorded within this trial and its follow-up, not every possible outcome or a definitive comparison. The registry record does not provide serious-event terms, additional detail on event ascertainment, or a comparative safety analysis. The absence of reported serious-event terms should not be interpreted as evidence about events beyond the posted record.
The record separately lists 11 other adverse events in the medication group and 3 in the placebo group. These counts are not serious adverse events, and the registry summary does not provide further detail about their nature or severity. Safety interpretation should distinguish these categories rather than combine them. In general, event counts from a trial of this size may be imprecise, and they should be read with the reported follow-up and ascertainment details in mind; those details are not fully reported in the registry record.
12. What the Result Does, and Does Not, Mean
The primary posted data describe average body-weight change within each randomized group from baseline to 3 months. They show a mean decrease in both groups, with separate 95% confidence intervals around each group mean. These statistics are informative about the observed group summaries, but they do not give a direct estimate of the difference between groups.
Accordingly, the primary result does not, on its own, quantify how much the groups differed or how precisely that difference was estimated. It also does not provide a reported primary hypothesis test. The group means should not be converted into a new contrast by subtracting one from the other; the registry record does not report that comparison. In general, the randomized treatment question is addressed most directly by an analysis of the between-group contrast, accompanied by its uncertainty and a clear description of the participants included.
The secondary outcomes broaden the scope to activity, tracker use and other measures, but only two have quantitative summaries with recalculated comparisons in the posted results. These unadjusted analyses are exploratory and do not establish that unreported outcomes were unchanged. The registry does not report a multiplicity approach or the analysis populations and missing-data methods needed to assess all results fully.
The adverse-event record reports no serious adverse events or deaths in either group, alongside other adverse-event counts. Those observations are limited to the events recorded in the trial; they do not establish the absence of risk or resolve comparative safety. Overall, the registry offers descriptive outcome information and selected secondary summaries, but important features of the primary comparison and analysis are not reported. The results should be interpreted within those reporting limits, rather than as a complete account of efficacy, safety or the trial’s statistical conclusions.
13. Why This Trial Matters Statistically
This trial illustrates a central distinction in clinical-trial reporting: separate arm-level estimates are not the same as a randomized comparison. The registry reports mean weight changes and confidence intervals for both groups, but does not report the primary difference between groups. Readers can see the direction and precision of each group mean while still lacking the estimate most directly tied to the randomized question.
The distinction matters because uncertainty around each mean is not interchangeable with uncertainty around a contrast. A comparative estimate accounts for the relationship between the groups and is the quantity needed to describe how much they differ under the analysis used. In general, confidence intervals help show precision, but their meaning depends on the estimand and method. Two arm-level intervals do not supply the missing contrast or its uncertainty.
The record also highlights the importance of clear analysis reporting. Without the analysis population, missing-data approach, multiplicity plan and primary comparison method, readers cannot fully evaluate how the reported summaries were obtained or how broadly they apply to randomized participants. Such information is especially helpful when a trial reports multiple secondary outcomes and some calculations are unadjusted.
Finally, planning illustrations derived from observed effects are not a substitute for a documented sample-size rationale. They can demonstrate, in general, how planning depends on assumptions and target effects, but they do not reveal the trial’s original design calculations. Separating descriptive results, confirmatory comparisons and planning exercises helps prevent overstatement and keeps attention on the information the registry actually reports.
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 of the posted primary results is the absence of a direct between-group estimate, confidence interval for that estimate, and reported test. The arm-level means and intervals describe the groups separately, so the comparative precision of the primary endpoint cannot be assessed from the registry record.
Further limitations concern analysis transparency. The registry does not report the primary analysis method, the analysis population, missing-data handling, covariate adjustment, or whether analyses followed a prespecified plan. The arm descriptions are blank, and details about treatment dosing, adherence, tracker use procedures and masking are not reported. These omissions make it difficult to connect the assigned interventions and study context to the population represented by each result.
Several secondary outcomes are listed, while quantitative comparative summaries are posted for only two. No sponsor-reported analyses are listed for those summaries, and no multiplicity procedure is reported. The recalculated comparisons are unadjusted and should be considered exploratory. The record also does not provide the numerical results for the other listed secondary outcomes, so the overall secondary-outcome pattern remains incomplete.
The trial enrolled 80 participants, and the outcome groups contain 42 and 38 participants. Those counts alone do not establish how many were randomized, how many completed follow-up, or whether every enrolled participant contributed to each endpoint. The registry does not provide participant flow or missingness details. Finally, the posted safety counts do not include further descriptions of the other adverse events or detailed serious-event ascertainment. These reporting gaps limit interpretation; they do not establish that any particular procedure was absent from the conduct of the trial.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Anti-Obesity Phentermine-Topiramate Extended Release Pharmacotherapy vs Placebo Among Patients Using a Wearable Activity Tracker — NCT04408586.
- Registry record last updated 2023-06-22; status last verified 2023-06.
- Results first posted 2023-06-22.
- 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 identifies a completed, Phase 4, randomized, double-masked, parallel-group trial sponsored by Mayo Clinic, with an enrollment of 80 participants. The comparison was phentermine-topiramate extended release versus placebo in a study involving wearable activity tracking, digital wellness devices and lifestyle recommendations.
The primary endpoint was mean body-weight change in kilograms from baseline to 3 months. The record reports group means and 95% confidence intervals, but not a direct between-group primary comparison. Secondary outcomes include measures of weight, activity, tracker use and health-related quality of life; quantitative comparative summaries are posted for exercise sessions and tracker usage. The registry does not report sponsor analyses for those secondary summaries, a multiplicity plan, analysis populations or missing-data methods.
The safety record reports zero serious adverse events and zero deaths in both groups. These counts describe the events recorded in the registry and do not by themselves establish comparative safety. Overall, the posted record supports descriptive reading of selected group outcomes, while leaving key details of the primary contrast and statistical analysis unreported.