Investigation of a New Diet for the Treatment of Obesity in the NHS: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Investigation of a New Diet for the Treatment of Obesity in the NHS (NCT05249439), a randomized na study. The primary outcome is Body Weight Change.

2. Clinical Question

The clinical question is framed as a randomized, parallel-group evaluation of a new weight-management programme against an established service. Random allocation can support a fair comparison when outcomes are observed and analyzed in both groups under appropriate methods. Here, the registry record reports that the primary outcome could not be analyzed for the control group. Consequently, the posted primary result is a one-group result rather than an estimate of the difference between programmes.

The record describes the treatment context as NHS specialist weight management and identifies obesity as the condition. It does not establish from the posted primary result whether the I-SatPro programme performed differently from the control programme. That requires a comparative estimate and its uncertainty, neither of which is reported for body-weight change.

3. Trial Design

This was a randomized, parallel-group study comparing I-SatPro with the established Imperial Weight Centre Tier 3 weight-loss programme. The record identifies Imperial College London as the sponsor and lists the phase as not applicable. Masking is listed as none, so this was an unmasked study. The record lists an enrollment of 21 and a completed status.

The study began on 2016-11-29, with primary completion listed as 2019-01. The primary outcome was body-weight change between the first patient group visit, defined as week 0, and the end of study at week 52. Weight change is a continuous outcome, and the registry lists the measure as a mean with standard error for dispersion.

The intervention was a group weight-management programme, described as equivalent in format to Tier 3 sessions. I-SatPro included dietary advice centered on low-carbohydrate, low-glycaemic-index eating, protein, healthy fats and avoiding high-sugar or processed foods. Participants were advised to eat in response to hunger and fullness rather than follow a defined calorie restriction. The programme also included content on fibre, meal timing, exercise, sleep, self-care and behavioural strategies. The comparator was the established Imperial Weight Centre Tier 3 group programme.

Although random allocation is listed, details of the allocation procedure, sequence generation and concealment are not reported in the registry record. The analysis population is described for the primary outcome: baseline and week 52 measurements were available for 10 I-SatPro participants, while no control participants were analyzed for weight change. The record does not report a reason that explains why the control outcome could not be analyzed.

The record lists secondary outcomes covering energy expenditure, body composition, blood pressure, HbA1c, eating patterns and hunger, eating behaviour, wellbeing and quality of life, and patient dropout. It lists eight posted secondary outcomes. Their numerical results are not included in the primary outcome information summarized by 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.

Before assignment: Three participants in the I-SatPro group were excluded for the following reasons: psychiatric (n=1), medical (n=1), literacy (n=1) Two participants dropped out. Ten participants in the I-SatPro arm completed the study. Primary outcome data were available for: n=10 Zero participants in the control arm completed the study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Baseline pre-dietary intervention and post-dietary intervention (week 52) data were available for n=10 participants in the I-SatPro group and body weight change was analyzed in these participants. No patients were analysed for the control group: it was not possible to analyze change in body weight for the control group at the end of the study (week 52) as these data were not collected because no participants remained in this arm of the study at this timepoint.

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 Body Weight Change, measured over First patient group visit (week 0) to end of study (week 52).

The primary endpoint is change in body weight, measured in kilograms from the first patient group visit at week 0 to the end of study at week 52. It is a continuous measure: each participant’s outcome is expressed as a weight change, and the group result is reported as a mean. The posted I-SatPro result is -12.99 kg, with a standard error of 1.7, among 10 analyzed participants.

Weight change is used because it directly describes the measured outcome targeted by a weight-management programme. A continuous measure retains the size and direction of changes rather than reducing them to categories. A negative change denotes weight loss under the stated change-from-baseline convention in the registry description. This interpretation concerns the direction of the recorded measurement; it does not by itself establish a programme effect compared with another group.

The endpoint is intended to span the intervention period specified in the record, from week 0 through week 52. Such a measure can describe change over that interval among participants with the required observations. Its value for comparing programmes depends on having outcome data in both randomized groups and a suitable between-group analysis. The posted record has no analyzed control group for this endpoint, so it cannot show whether the observed I-SatPro change differs from change under the established Tier 3 programme.

The registry reports standard error as the measure of dispersion for the mean. Standard error describes the precision of a group mean estimate, not the spread of individual participant outcomes. Individual-level variability is not reported in the primary result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General: continuous outcomes and group means. A continuous outcome can take a range of values, such as weight change measured in kilograms. A group mean gives the average outcome among the analyzed participants. It does not show how individual outcomes are distributed. The registry reports the I-SatPro mean change as -12.99 kg for 10 participants.

General: standard error. Standard error describes the statistical precision of an estimated mean. It is different from the standard deviation, which describes variation among individual observations. A smaller standard error generally indicates a more precisely estimated mean under the analysis assumptions. Here, the registry reports a standard error of 1.7, but does not report the individual-level distribution or a confidence interval.

General: confidence intervals. A confidence interval gives a range of values compatible with the data and a specified statistical procedure. It communicates uncertainty about an estimate in the same units as the outcome or contrast. No confidence interval is reported for the primary result, and there is no posted interval for a comparison between groups. Without those estimates, the range of plausible comparative effects cannot be read from the registry results.

General: interpreting a p-value. A p-value describes how compatible the observed data are with a specified null hypothesis under the statistical model used. It does not measure the probability that the null hypothesis is true, the size of an effect, or the probability that a result will be reproduced. Its meaning depends on the tested contrast and analysis. The registry lists a two-sided t-test and p < 0.001, but the exact null hypothesis is not reported in the registry record. Because the analysis is listed for I-SatPro alone, the p-value should not be interpreted as a test of the difference between I-SatPro and control.

General: two-sided t-tests. A t-test can be used to assess evidence about a mean or difference in means, depending on how the test is specified. A two-sided test considers departures in either direction from its null value. The registry names a two-sided t-test but does not report enough detail to identify fully the tested contrast, assumptions, or handling of missing data. The label “Mean Difference (Final Values)” appears in the reported analysis, while the group listing contains I-SatPro only. The registry record does not clarify that apparent scope.

General: randomized comparisons. Randomization is a design method intended to make treatment groups comparable on average at the start of a study. A randomized design supports causal comparisons when outcomes are collected and analyzed in both groups using an appropriate plan. In this record, randomization is listed, but no control participants were analyzed for the primary weight-change endpoint. The within-group I-SatPro result therefore does not estimate the effect of assignment to I-SatPro relative to assignment to the established programme.

General: over-dispersion. Over-dispersion occurs when observed variability is greater than a statistical model assumes. It can make standard errors too small and uncertainty appear narrower than it is if the model does not account for the extra variability. The posted endpoint is continuous, and the registry does not report a model assessment or evidence about over-dispersion. This concept is relevant generally, but there is no basis in the record to conclude that over-dispersion affected this analysis.

General: missing outcomes and analysis populations. When outcome data are missing, the analyzed group may differ from the randomized group. The effect of that difference depends on why measurements are missing and how the analysis handles them. The registry reports baseline and week 52 data for 10 I-SatPro participants and says no control participants were analyzed for body-weight change. Reasons, missing-data methods and a full participant flow are not reported in the registry record. The primary result therefore applies directly to the analyzed I-SatPro participants, while its relation to all randomized participants remains uncertain.

Planning illustrations. The planning illustrations use the observed effect as a basis for considering hypothetical future sample sizes; they are not a report of the trial’s original design justification and are not observed power. Their stated assumptions are a two-sided significance level of 0.05, equal allocation, a normal approximation and an effect set as a fraction of the observed effect. Such illustrations depend on those assumptions and on the observed estimate, which may be uncertain. The trial’s own sample-size justification is not reported in the registry record.

Analyses not documented. The registry lists one primary analysis and gives a sponsor analysis, but it does not report an analysis plan, interim analyses, adjustment methods or a detailed account of the statistical model. Those omissions limit assessment of whether the posted analysis followed a prespecified plan and how the reported inference was obtained.

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.

R code and output

arm <- c("I-SatPro")
n   <- c(10)
m   <- c(-12.99)
sp  <- c(1.7)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  I-SatPro  10  -12.990  5.376  -16.836  -9.144

11. Analyses Reported by the Sponsor

The registry lists the sponsor’s analysis as a two-sided t-test for the I-SatPro group, with the parameter labeled “Mean Difference (Final Values).” It reports -12.99 and p < 0.001. The posted arm result also gives a mean body-weight change of -12.99 kg among 10 analyzed participants, with a standard error of 1.7. The record indicates no discrepancy between the sponsor analysis and the posted result.

That agreement supports reading the sponsor’s reported value as consistent with the posted I-SatPro result. It does not turn the analysis into a comparison with control. The reported analysis lists I-SatPro alone, and no control participants were analyzed for body-weight change. The sponsor’s result therefore cannot supply the missing control-group estimate or a between-group confidence interval.

The registry’s label “Mean Difference (Final Values)” does not specify the null hypothesis or explain how the test was constructed. The exact inferential meaning of the sponsor’s p-value is not reported in the registry record. It should not be treated as a test of superiority over the Tier 3 programme based on the available record.

Because the registry indicates no discrepancy, there is no conflicting sponsor estimate that would require a recalculated result to take precedence. The key limitation remains the lack of a control analysis, rather than a disagreement between two posted numerical estimates.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint of body-weight change and eight posted secondary outcomes. Those secondary outcomes cover energy expenditure, body composition, blood pressure, HbA1c, eating patterns and hunger, eating behaviour, wellbeing and quality of life, and dropout. When a study examines multiple outcomes or multiple analyses, the chance of at least one nominally unusual result can increase. Statistical methods may address this through a prespecified hierarchy or an adjustment procedure, but the registry record does not report a multiplicity strategy.

The absence of a reported strategy does not establish that no adjustment was planned or performed; it means the record does not document one. The primary result should therefore be interpreted according to its stated endpoint and analysis, without assuming how the sponsor handled multiple outcomes. Numerical secondary results and their inferential details are not included in the primary outcome information described in the registry record.

Missing outcome information is central to interpretation. The record says baseline and week 52 measurements were available for 10 participants in I-SatPro and that no control participants were analyzed for the primary endpoint. It does not report why control change could not be analyzed, how many randomized participants had missing measurements by reason, or what methods were used to handle missing data. It also does not report whether any alternative analysis population or sensitivity analysis was used.

These gaps matter because analysis of participants with observed outcomes can differ from analysis of all randomized participants. If the likelihood of having a measurement is related to outcomes or group assignment, a complete-case result may not represent the full randomized group. The registry record does not provide information to assess that possibility or its direction.

The record does not report a detailed analysis population definition beyond the stated availability of baseline and week 52 data for the I-SatPro participants. The number randomized to each group is not stated in the primary outcome description, although safety counts are separately listed. Those safety counts should not be substituted for the primary endpoint analysis population. The full allocation flow and reasons for exclusions are not reported in the registry record.

13. Safety Results

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

Deaths

Other (non-serious) adverse events

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

For serious adverse events, the registry lists 15 participants at risk in I-SatPro and 6 in control, with 0 affected participants in each group and 0 deaths in each group. For other adverse events, it lists the same at-risk counts and 0 affected participants in both groups. These are the posted counts; they do not describe the primary body-weight analysis population.

“At risk” identifies the group size used for the safety reporting in the registry, while “affected” is the count recorded as experiencing the specified event category. The record does not list serious adverse event terms, and it does not provide additional detail about how events were monitored, classified or attributed. A zero count in the posted registry entry means no events were recorded in that category for those listed participants; it does not establish that an event was impossible or that there was no safety uncertainty.

The safety figures should be read separately from the primary efficacy endpoint. They do not address whether the weight-change result differs between programmes, and they do not repair the absence of an analyzed control group for that endpoint. The record’s safety counts are descriptive and should not be interpreted as a comparative safety estimate beyond the event counts stated.

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

The posted primary outcome shows that the analyzed I-SatPro participants had a mean body-weight change of -12.99 kg from week 0 to week 52. The standard error is 1.7, and the analysis includes 10 participants with baseline and week 52 data. This result describes change among those participants under the registry’s analysis; it does not, by itself, estimate the effect of I-SatPro relative to the established Tier 3 programme.

The study was randomized, but a randomized design only permits a comparative interpretation when a suitable outcome analysis is available for both groups. No control participants were analyzed for this endpoint, and the registry says it was not possible to analyze control-group weight change. Thus, the posted data cannot establish the direction or size of a between-programme difference. They also cannot show whether the observed I-SatPro change would have differed from the change under the comparator during the same interval.

The reported p-value, < 0.001, belongs to an analysis listed for I-SatPro alone. The precise null hypothesis is not reported in the registry record. It must not be presented as evidence that I-SatPro is more effective than control. A p-value also does not communicate the size or practical importance of an outcome, and no confidence interval is reported for the mean or a treatment contrast.

The result applies to participants included in the analysis. It cannot automatically be extended to all enrolled or randomized participants because the record does not give a full account of missing outcomes or reasons for non-analysis. It also does not establish how the result would generalize to other services, populations or settings.

Secondary outcomes could provide additional context about body composition, blood pressure, blood sugar, eating patterns and wellbeing, but their numerical findings are not part of the posted primary result. The registry lists those outcomes without supplying their results in this record. The appropriate reading is therefore narrow: a mean weight decrease was recorded among the analyzed I-SatPro participants, while the comparative primary question remains unanswered by the posted data.

15. Why This Trial Matters Statistically

This trial raises a fundamental issue in clinical-trial interpretation: a striking within-group change is not the same as an estimated treatment effect. The study’s randomized parallel-group design asks for a comparison between I-SatPro and the established Tier 3 programme. Yet the posted primary outcome result comes from I-SatPro participants alone. The missing control result prevents the central randomized comparison from being quantified.

The distinction matters because participants may change over time for reasons beyond the assigned programme. In a randomized comparison, outcomes in the control group help establish the change that occurred under the comparator over the same period. Without that result, the I-SatPro mean cannot separate programme-related change from other influences. This is a general statistical principle, not a claim about what happened in this study.

The record also illustrates why the analysis population and missing measurements belong alongside an effect estimate. The I-SatPro result is based on participants with baseline and week 52 data; no control participants were analyzed. The reasons and handling of missing measurements are not documented in the registry record. Those details affect how confidently the analyzed result can be related to the randomized groups.

Finally, the registry’s p-value is not a substitute for a between-group estimate or its uncertainty. Statistical evidence is interpretable only in relation to the contrast and model that generated it. The analysis is listed for one group, while the clinical question is comparative. Recognizing that distinction prevents a within-group finding from being overstated as a result about comparative effectiveness.

16. 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 main trial-specific limitation is that no control participants were analyzed for the primary body-weight outcome. As a result, the registry provides no primary between-group estimate, confidence interval or direct comparison of I-SatPro with the established Tier 3 programme. The record states that control change could not be analyzed but does not explain why.

The primary estimate is based on 10 I-SatPro participants with baseline and week 52 data. The registry does not provide a full participant flow, reasons for missing measurements, a detailed analysis population definition or sensitivity analyses. It is therefore not possible to assess how the analyzed participants relate to all randomized participants or whether missingness could have influenced the reported mean.

The sponsor analysis is labeled “Mean Difference (Final Values)” and gives a two-sided t-test, but the exact null hypothesis and test construction are not reported in the registry record. No confidence interval is reported for the primary result. These omissions limit evaluation of the precision and inferential meaning of the reported analysis.

The record lists secondary outcomes, but their numerical findings are not included in the primary outcome information. It does not report a multiplicity strategy, detailed statistical analysis plan, interim analyses, sample-size justification, allocation sequence procedures or concealment. These details should not be inferred from the design label or from planning illustrations based on the observed effect.

Masking is listed as none. The record does not describe whether outcome assessment was otherwise protected from knowledge of group assignment. The intervention is a behavioural programme with multiple components, but adherence and exposure details are not reported in the primary outcome information. These limits constrain interpretation of the posted result and its applicability beyond the analyzed participants.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Investigation of a New Diet for the Treatment of Obesity in the NHS — NCT05249439.
• Registry record last updated 2025-03-21; status last verified 2025-03.
• Results first posted 2025-03-21.
• 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.

20. Record Summary

The registry record describes a completed, randomized, unmasked, parallel-group study sponsored by Imperial College London, with an enrollment of 21. It compares the I-SatPro weight-loss programme with the established Imperial Weight Centre Tier 3 programme. The primary endpoint is body-weight change from week 0 to week 52.

Among 10 I-SatPro participants with baseline and week 52 data, mean change was -12.99 kg, with a standard error of 1.7. A two-sided t-test is listed with p < 0.001. No control participants were analyzed for the primary endpoint, so the posted result does not provide a between-group estimate. The registry does not report a confidence interval or clarify the precise null hypothesis for the listed test.

The record lists secondary outcomes and safety counts, including 0 serious adverse events and 0 deaths in both groups. It does not report a detailed missing-data account, multiplicity strategy, statistical analysis plan or sample-size justification. The principal statistical conclusion is limited to observed change among the analyzed I-SatPro participants; comparative weight-change evidence is not reported in the registry record.