The biology underlying these conditions centers on the melanocortin 4 receptor pathway, a critical signaling cascade in the hypothalamus that governs energy balance and appetite. Under normal circumstances, the hormone leptin binds to leptin receptors on the surface of pro-opiomelanocortin neurons, triggering a chain of signaling that ultimately activates melanocortin 4 receptor neurons. These neurons send satiety signals that suppress food intake and increase energy expenditure. When any step in this pathway fails, whether through a genetic mutation in the leptin receptor gene, loss of pro-opiomelanocortin production, the pleiotropic genetic disruptions of Bardet-Biedl syndrome, or structural damage to the hypothalamus itself, the result is hyperphagia: a chronic, pathological state of insatiable hunger and impaired satiety that drives persistent food-seeking behavior and severe, early-onset obesity.

Until recently, there was no effective treatment aimed at this pathway, and no universally accepted way to measure hunger from the patient’s perspective. Existing appetite questionnaires were developed for people with common obesity who have intact melanocortin signaling, making them poorly suited to capture the extreme hunger experienced by patients with pathway diseases. That changed with the development of setmelanotide, an MC4R agonist that is currently the only US Food and Drug Administration-approved therapy targeting this pathway in patients aged two years and older with syndromic or monogenic obesity due to Bardet-Biedl syndrome, leptin receptor deficiency, pro-opiomelanocortin deficiency, or acquired hypothalamic obesity. In phase 3 trials, patients treated with setmelanotide achieved significant weight loss alongside marked reductions in hunger, making hunger itself a legitimate and important treatment outcome.

To measure that outcome, researchers created the Daily Hunger Questionnaire, a three-item patient-reported instrument addressing morning hunger, average hunger, and the single most intense hunger experienced over the previous 24 hours. The Most Hunger item, which asks patients to rate their peak hunger on an 11-point scale from zero, meaning not hungry at all, to ten, meaning hungriest possible, was designated a key secondary endpoint in the setmelanotide phase 3 trials under agreements with the FDA’s Division of Diabetes, Lipid Disorders, and Obesity. The new study set out to establish whether this item truly works: whether patients understand it, whether it produces consistent and meaningful scores, and how much change on the scale represents a difference that patients actually feel.

The qualitative phase involved three separate interview studies, each aligned with FDA guidance on patient-focused drug development. Patients with leptin receptor or pro-opiomelanocortin deficiency were interviewed face-to-face at a German clinical site before entering the setmelanotide trials, while patients with Bardet-Biedl syndrome and acquired hypothalamic obesity were interviewed by telephone or video after participating in their respective trials, allowing them to compare hunger before and during treatment. Cognitive debriefing confirmed that participants across all three groups understood the Most Hunger item and could answer it with reasonable consistency. When asked to describe what a ten on the scale meant, patients spoke of an unrelenting hunger that impaired their ability to function, while a five was generally considered a tolerable level. Participants with Bardet-Biedl syndrome reported a mean pre-treatment score of 8.8, and those with acquired hypothalamic obesity reported a mean of 8.5, scores that patients associated with an all-consuming desire for food and extreme food-seeking behaviors such as sneaking or hiding food.

The quantitative phase analyzed data from four phase 3 trials, registered under ClinicalTrials.gov identifiers NCT03287960, NCT02896192, NCT03746522, and NCT05774756. Participants recorded their hunger daily at home using an electronic diary for seven consecutive days before each clinic visit, and weekly averages were computed for analysis. At baseline, mean weekly Most Hunger scores ranged from 6.9 to 7.5 across the disease groups, and by the end of treatment, patients had improved by an average of 2.3 to 3.3 points. Test-retest reliability, assessed by comparing scores from two consecutive weeks in the absence of any expected change, yielded intraclass correlation coefficients of 0.51 for the pooled leptin receptor and pro-opiomelanocortin deficiency group, 0.59 for Bardet-Biedl syndrome, and 0.80 for acquired hypothalamic obesity. The authors note that the lower estimates in the rarer genetic diseases likely reflect the very small samples and the homogeneity of responses, which can depress reliability statistics, rather than any inherent flaw in the measure.

Construct validity was supported by convergent correlations between the Most Hunger item and the Patient Global Impression of Severity, a four-point anchor measure administered at clinic visits. In the leptin receptor and pro-opiomelanocortin deficiency group, correlations with the PGIS were strong at later timepoints, reaching 0.75 at week 13 and 0.86 at week 53, while the acquired hypothalamic obesity group showed a strong baseline correlation of 0.74 and a moderate to high end-of-treatment correlation of 0.57. Known-groups analyses in the hypothalamic obesity cohort showed statistically significant differences in Most Hunger scores across PGIS severity categories, with mean scores falling from 7.0 in the moderate hunger group to 4.9 in the mild hunger group at baseline. In the Bardet-Biedl syndrome population, however, correlations with the PGIS were negligible, a discrepancy the authors attribute to ceiling effects on the hunger item and restricted use of the PGIS severity categories, which limited the ability to detect associations.

Perhaps the most clinically consequential output of the study is the estimation of meaningful within-patient change thresholds, the amount of score change that corresponds to a difference patients perceive as meaningful. Using anchor-based methods with a one-point improvement on the PGIS and the much less hungry category of the Patient Global Impression of Change as anchors, the researchers estimated thresholds of 1.5 to 2.6 points for patients with leptin receptor or pro-opiomelanocortin deficiency and 2.4 to 3.7 points for those with acquired hypothalamic obesity. For Bardet-Biedl syndrome, weak responsiveness between the Most Hunger item and the global anchors prevented direct estimation, so the team turned to the closely correlated Morning Hunger item, deriving a preliminary threshold range of 0.95 to 1.6 points. The authors caution that because the trial populations and designs differed, these thresholds should not be compared across diseases as indicators of differing treatment sensitivity; they simply provide context for interpreting individual patient improvement in future trials.

Beyond the psychometrics, the study delivers a striking portrait of what it feels like to live with a broken satiety pathway. Across all four diseases, patients described essentially the same experience: scores of seven to nine before treatment, an intrusive and relentless preoccupation with food, and behaviors consistent with hyperphagia. After setmelanotide, mean weekly scores settled between four and five, and patients described the reduction as life changing, reporting improved focus and mood, decreased food-related anxiety, better family and social relationships, and renewed participation in hobbies and interests. The convergence of qualitative and quantitative evidence across such distinct etiologies, genetic and acquired alike, strengthens confidence that the Most Hunger item captures a shared, biologically grounded phenomenon rather than a disease-specific quirk.

The work also has clear forward momentum. On the basis of the evidence supporting the item in patients aged 12 and older, the team reports that a caregiver-reported version for children under 12 is currently in development, extending the measurement framework to younger patients who often bear the earliest and heaviest burden of these diseases. Limitations remain, including the small samples inherent to rare disease research, the absence of sex and gender analyses, and potential recall bias in interviews conducted at varying intervals before treatment or before hypothalamic injury. The psychometric analyses also used blinded pooled data across treatment and placebo groups and were not designed to evaluate efficacy. Even so, the study establishes the Most Hunger item as a fit-for-purpose patient-reported outcome for measuring hunger in MC4R pathway diseases, giving future trials a validated yardstick for one of the most disabling symptoms in medicine and giving patients a way to make an invisible, internal experience count in the evaluation of new therapies.

Subject of Research: Development and psychometric validation of a patient-reported hunger measure for rare MC4R pathway obesity diseases

Article Title: Measuring Hunger Severity in Rare MC4R Pathway Diseases: Development and Psychometric Evaluation of the Most Hunger Item

Article References: Clément, K., Roth, C. L., Kühnen, P., Haqq, A. M., Mallya, U. G., Ervin, C., Norcross, L., Bhargava, S., Argente, J., & Miller, J. L. (2026). Measuring Hunger Severity in Rare MC4R Pathway Diseases: Development and Psychometric Evaluation of the Most Hunger Item. Advances in Therapy. https://doi.org/10.1007/s12325-026-03741-x

Image Credits: AI Generated

DOI: 10.1007/s12325-026-03741-x

Keywords: MC4R pathway, hyperphagia, setmelanotide, Bardet-Biedl syndrome, POMC deficiency, LEPR deficiency, hypothalamic obesity, patient-reported outcome, psychometric validation, rare disease, obesity, hunger measurement