Background Chronic gastroduodenal symptoms are challenging to diagnose and treat. Body surface gastric mapping provides non-invasive biomarkers of gastric function, but the requirement of a standard meal for postprandial assessment can be difficult for severely symptomatic patients.

Aims To assess the impact of reduced meal sizes and fasting on body surface gastric mapping metrics to determine clinical interpretability under non-standard nutritional loads.

Methods Healthy controls (n=60) underwent a 4.5-hour Gastric Alimetry test. Three age, sex, and BMI-matched groups (n=20 each) were compared: Standard Meal (482 kCal), Nutrient bar + Water (250 kcal), and Fasted (no meal). Principal Gastric Frequency, Gastric Alimetry Rhythm Index, BMI-Adjusted Amplitude, and fed:fasted Amplitude Ratio were analyzed against normative intervals.

Results Meal status significantly affected amplitude-based metrics; the Standard Meal group exhibited higher BMI-Adjusted Amplitude (p<0.001) and fed:fasted Amplitude Ratio (p=0.001) than Fasted and Bar + Water groups. Frequency and rhythm-based metrics were resilient; Principal Gastric Frequency (p=0.245) and Gastric Alimetry Rhythm Index (p=0.336) showed no significant differences across conditions. While amplitude deviations were common in the Fasted group (20% fell below the normative range), Gastric Alimetry Rhythm Index and Principal Gastric Frequency remained within normal reference ranges for 95% of participants across all conditions.

Conclusions While consuming <50% of the standard meal significantly reduces gastric amplitude, gastric rhythm remains stable. Principal Gastric Frequency and Gastric Alimetry Rhythm Index function as reliable biomarkers of gastric myoelectrical function regardless of nutritional state.

Statements and Declarations: Competing interests: GOG and AG hold intellectual property and grants in gastric electrophysiology and are Directors of University of Auckland spin-out company Alimetry. SC, GS, and ND hold intellectual property in GI electrophysiology. ML, BW, CD, SS and CNA are members of Alimetry Ltd. The remaining authors have no relevant conflicts to declare.

This study is funded by a New Zealand Health Research Council Programme Grant 3715588.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethical approvals were granted by the Auckland Health Research Ethics Committee (AHREC; AH1130), the University of Calgary Conjoint Health Research Ethics Board (REB19-1925), and the University of Louisville Institutional Review Board (IRB: 20.0962; 737935).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

Statements and Declarations:

Competing interests: GOG and AG hold intellectual property and grants in gastric electrophysiology and are Directors of University of Auckland spin-out company Alimetry. SC, GS, and ND hold intellectual property in GI electrophysiology. ML, BW, CD, SS and CNA are members of Alimetry Ltd. The remaining authors have no relevant conflicts to declare.

Funding: This study is funded by a New Zealand Health Research Council Programme Grant 3715588.

All data produced in the present work are contained in the manuscript