Identification of Nutrition-Focused Physical Exam and Other Nutrition Assessment Components Specific to Bariatric Surgery: A Modified Delphi Study

Abstract

Bariatric surgery (BS) is effective for treating obesity but carries significant nutritional risks. Patients often develop micronutrient deficiencies, loss of muscle mass, and other physiological complications. Standardized methods such as the Nutrition-Focused Physical Exam (NFPE) may not adequately capture physical findings specific to BS. This study aimed to develop an expanded and modified bariatric-specific NFPE tool and achieve expert consensus on its essential components using a modified Delphi methodology. A literature review identified clinical signs of malnutrition and nutritional complications unique to patients undergoing BS, which informed proposed BS-NFPE components. A three-round modified Delphi study with expert bariatric dietitians (n = 25) achieved consensus (≥75% agreement) on 43 BS-NFPE components, including physical signs of micronutrient deficiencies and toxicities, changes in muscle and fat stores, indicators of surgical complications, gastrointestinal symptoms, and mental health effects. Experts also supported incorporating functional considerations and social determinants of health. This study introduces the first evidence-informed modified BS-NFPE tool to address limitations of the standard NFPE in bariatric populations. Use of BS-specific features may help clinicians identify malnutrition earlier, tailor care, and improve long-term patient support. Future research should evaluate this tool in clinical practice.

1. Introduction

Although bariatric surgery (BS) can result in substantial weight loss, ensuring adequate nutritional status pre- and post-operatively is critical to achieving long-term health and sustained success. BS is an established and effective treatment for achieving clinically meaningful and lasting weight loss in individuals with obesity, resulting in 40–71 percent excess weight loss [1]. Mortality and severe complication rates are relatively low at 0.1 percent and 4 percent, respectively [2]. However, over 70 percent of patients develop micronutrient deficiencies within the first three years post-surgery due to insufficient intake, altered gastrointestinal (GI) anatomy, and the potential for malabsorption, depending on the surgical approach [3,4]. Also, many patients have pre-existing, undetected deficiencies, compounding the risk of post-operative malnutrition [5]. Beyond micronutrient concerns, approximately one-third of post-surgical weight loss is attributed to metabolically active tissue loss, particularly muscle mass, placing patients at risk for sarcopenia and weight recurrence [6,7]. Muscle wasting and diminished bone integrity have been linked to frailty and long-term health complications [6,7,8,9,10]. Even fat loss can have adverse effects, such as eustachian tube dysfunction, which affects hearing, and mesenteric artery syndrome, which contributes to GI obstructions [11,12]. Surgical and additional GI complications such as anastomotic leaks, other causes of GI obstructions, rapid gastric emptying, and post-bariatric hypoglycemia (PBH) can significantly impact nutritional status [13,14,15,16,17,18]. The challenges encountered by patients who have BS are not limited to physiology. Psychological well-being and social determinants of health affect weight loss success and quality of life (QOL) [19,20,21,22,23]. Early identification and intervention for these multifactorial risks is essential to improving long-term outcomes and potentially minimizing morbidity and mortality [24,25].

Standard BS procedures include vertical sleeve gastrectomy (VSG), which poses a risk of increased gastroesophageal reflux disease (GERD), and the Roux en Y gastric bypass (RYGB), which poses a higher risk of PBH, GI ulcers, and intestinal obstructions [26]. Procedures performed less frequently, including the biliopancreatic diversion (BPD) and the single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S), have a higher risk of nutritional deficiencies [27]. Although it was once popular, surgeons infrequently perform the laparoscopic gastric band (LGB) due to inadequate weight loss and higher complication rates [28]. While endoscopic procedures such as intragastric balloons are also considered less invasive BS options, they are beyond the scope of this research [26]. See https://asmbs.org/for-patients/explore-conditions-procedures/ (accessed on 19 April 2026.) for images and summaries of the bariatric procedures.

The Nutrition-Focused Physical Exam (NFPE) is a key tool used by registered dietitian nutritionists (RDNs) for assessing nutritional status utilizing inspection, palpation, percussion, and auscultation to evaluate physical signs of malnutrition and nutrient deficiencies [29]. The standard exam encompasses a comprehensive review of body composition, including fat and muscle loss, and fluid status, as well as clinical signs of deficiencies affecting the oral cavity, hair, skin, and nails [30]. However, identifying malnutrition after BS presents challenges. These include challenges in assessing body composition due to increased adiposity and obscured physical landmarks, as well as difficulty differentiating excess skin from underlying muscle or fat following significant weight loss [31]. While the Accreditation Council for Education in Nutrition and Dietetics (ACEND) requires NFPE training, the standard NFPE lacks sensitivity for identifying nutritional complications specific to BS [32].

Despite a 3.5 percent decline in bariatric procedures since 2022 coinciding with the introduction of GLP-1 (Glucagon-Like Peptide-1) medications, there were still 270,000 bariatric surgeries performed. This highlights the continued need for tailored nutritional care before and after BS [33]. This population needs a specialized, evidence-informed approach to nutrition assessment. This study aimed to bridge that gap. The first objective was to develop an expanded and modified bariatric-specific NFPE (BS-NFPE) tool informed by a comprehensive literature review. The proposed tool is non-validated and could be described as a conceptual framework for nutritionally assessing this population. The tool will not be diagnostic but will include complications of surgery that could impact one’s nutritional status. The second objective was to utilize a modified Delphi methodology to achieve expert consensus among bariatric RDNs on the essential components of this tool. The goal is to equip clinicians with a more precise and clinically relevant framework for identifying nutritional risk and optimizing care for patients undergoing BS.

2. Materials and Methods

The researchers reviewed the existing literature with the aid of a medical librarian to uncover additional components of the standard NFPE that could assess the full impact of BS on nutritional status. Searches were performed in PubMed, CINAHL, Scopus, and Web of Science electronic databases. Research designs of all types were included, excluding editorials, dissertations, and newspaper articles. All bariatric surgeries were included, except for the LGB, which is rarely performed [34]. Eligible studies examined physical or psychological assessments following BS, were written in English, and conducted in human subjects. The search spanned the last 20 years, during which BS became prominent, to allow for a thorough review. After a thorough review of the literature, a total of 418 articles were obtained that supported the research.

A questionnaire was developed in Qualtrics using the identified six domains and their respective components (

Table 1. Initial Six Domains and Respective Components.

Domains (D)	D1: Micronutrients	D2: Body Habitus	D3: Frailty	D4: Surgical Complications	D5: GI Complications	D6: Mental Health
Components	Vitamin A	Muscle	Frailty	GI Bleeding	Inadequate Intake	Depression
	Vitamin D	Fat		DVT/PE	Diarrhea	Transfer Addiction
	Vitamin E	Bone		Ulcers	Constipation	Eating Disorders
	Vitamin K	Hydration		Reflux	Dumping Syndrome
	Thiamine			Skin Infections
	Vitamin B12/Folic Acid			Anastomotic Leaks
	Vitamin C			GI Obstructions
	Calcium			GI Fistulas
	Iron			Gout
	Zinc			Gallstones
	Copper			Kidney Stones
	Selenium

Abbreviations: D, domains; DVT, deep vein thrombosis; GI, gastrointestinal; PE, pulmonary embolus.

) as proposed assessment areas for patients before and after BS [35].

Beyond the standard NFPE, the domains and related components that needed to be added were as follows: 1. Micronutrient deficiencies (fat-soluble vitamins, Vitamin B12, folic acid, Vitamin C, calcium, iron, zinc and copper); 2. Body Habitus (muscle, fat, bone, and hydration); 3. Frailty (frailty); 4. Surgical Complications (GI bleeding, deep vein thrombosis (DVT)/pulmonary embolism (PE), GI ulcers, reflux, skin infections, anastomotic leaks, GI obstructions, GI fistulas, gout, gallstones, and kidney stones); 5. GI Complications (inadequate intake, diarrhea, constipation, and dumping syndrome); and 6. Mental Health (depression, transfer addiction, and eating disorders). The initial survey is included in Supplementary File S1. Consensus was ascertained by rating level of agreement for usefulness (provides actionable clinical information) and relevance (aligns with bariatric patient needs) on each assessment domain or category and component on a 5-point Likert-scale ranging from 1 (strongly disagree) to 5 (strongly agree). Open-ended fields allowed participants to explain responses and suggest modifications, exclusions, or additions. The survey was tested among a small group of research advisors and colleagues who were not involved in the Delphi rounds. Feedback from the pre-test was used to revise the survey for clarity, function, and flow.

A modified Delphi methodology was selected to achieve expert consensus on the domains and components of a BS-NFPE. This approach is frequently used in healthcare research, particularly when evidence is limited, research is ethically or logistically challenging, or findings are inconsistent [36]. The Delphi method is often used to establish evidence-based guidelines, identify assessment indicators, and develop clinical tools [36]. Researchers use the Delphi method to gather expert opinions through multiple rounds of surveys. After each round, responses are summarized and shared with panelists anonymously, allowing them to revise their answers based on group feedback. Iterations are conducted until a consensus is established or if opinions remain polarized at the conclusion of the maximum planned three rounds of surveys [36,37].

A Delphi study is considered of higher quality if it defines consensus and does so a priori [38]. Consensus was defined before the study began as agreement from at least 75 percent of panelists (ratings of 3 or higher on the Likert scale) or ratings within ± 1 standard deviation (SD) of the mean which is in line with common Delphi methodology [39]. There is no agreement in the literature on what constitutes consensus when doing a Delphi study. Shang et al. [40] recommend 70–80 percent agreement among panelists [40]. Hsu and Sanford concur that a consensus of 75 percent is considered rigorous [41]. The use of a Likert scale rating of ≥3 (neither agree nor disagree) ensured that retained components were useful and relevant, while balancing rigor with inclusivity in tool development.

The authors chose purposive sampling for this project because RDNs with expertise in BS were needed [42]. A homogeneous group increases the reliability of the responses and allows for fewer panelists when researching complex topics [43]. Researchers recommend a sample size of ten or more for modified Delphi studies, with 30–50 being the most commonly suggested range [42,44]. However, Jorm et al. suggest 20 as a common goal [45]. This project aimed for 30 panelists to account for attrition and ensure reliable data.

Snowball sampling, also known as chain or network sampling, was employed to identify experts in the field [46]. Several known RDNs specializing in BS were asked to take part in the study and to refer colleagues who met the inclusion criteria. Eligibility required at least five years of experience working with adults in BS. Guidance for conducting and reporting Delphi studies notes that representation from the relevant professional discipline is a primary criterion for expert selection. [47]. Individuals with less experience, working only in pediatric BS or practicing outside the field of nutrition, were excluded. Contact information was collected until a minimum of 30 potential panelists were identified.

The Scientific Review Board (SRB) and the Institutional Review Board (IRB, Study ID: Pro2024002479) provided ethical clearance, and participants consented to participate in the study electronically. Panelists were informed of the minimal risks, including the potential for a breach of confidentiality, despite the research team de-identifying personal information. The decision to participate in the study was entirely up to each panelist, and they were free to leave the study at any time without facing any penalty or consequence.

In the first round, panelists signed an informed consent form that outlined the research objectives and potential risks associated with this study. The form ensured that participants understood and agreed to participate in the study. Panelists also answered demographic questions on age, ethnicity, race, gender, years of experience as an RDN and bariatric specialist, specialty certifications, and their comfort level and frequency in evaluating nutrition-related physical findings. Additionally, in Round 1, panelists were given two weeks to respond to statements of usefulness and relevance by rating their level of agreement and completing open-ended responses on the six domains and their respective components, as outlined in Table 1. The research team used Qualtrics to evaluate the quantitative data and recorded the qualitative responses in a password-protected Excel spreadsheet. Rounds 2 and 3 allowed panelists to evaluate new and revised domains and components. Researchers conducted an additional literature review before sending out subsequent survey rounds to ensure that modifications and additional feedback were evidence-based.

The reports sent to panelists in rounds one through three are outlined in Supplementary Files S2–S4, respectively. These reports included the individual panelist’s scores compared to the mean, standard deviation (SD), interquartile range (IQR), percentage agreement, and whether the domain or component met consensus. Additionally, the reports included all de-identified qualitative data, including explanations of responses and recommended edits. Panelists also had the opportunity to clarify any comments by sending a return email to the research team. All domains and components that reached consensus were no longer available for a response in the following round of surveys. In the initial research design, the feedback would have allowed the panelists to reflect on group responses before reassessing the remaining items; however, 100 percent of the initially proposed domains and components met consensus in Round 1. Nonetheless, several recommended additions and edits allowed for a second and third round of revisions. See Supplementary File S5 for Round 2 and Supplementary File S6 for the Round 3 surveys.

The Delphi process concluded in Round 3 when all originally and newly proposed domains and components met consensus, and panelists addressed all recommended edits. After the final round, the study team created the finalized BS-NFPE tool, incorporating all domains and components that achieved consensus and included suggested edits. See Supplementary File S7 for the finalized BS-NFPE tool.

Frequencies were used to summarize participant demographics through descriptive statistics as categorical data. The researchers also assessed clinical ratings of usefulness and relevance for each component using descriptive statistics, including the mean, interquartile range (IQR), and percentage of agreement. Qualitative data from the open responses were analyzed and categorized using content analysis to identify common themes.

3. Results

The literature review identified six domains related to the impact of BS on nutritional status, as presented in Table 1. Of the 43 experts invited, 27 met the eligibility criteria and completed the first round, 26 the second, and 25 the third round of surveys. All panelists were white and non-Hispanic. The majority were females aged 30–49 years. Half held the Certified Specialist in Obesity and Weight Management (CSOWM) credentials or met the criteria to sit for the exam. Most had 5–15 years of BS experience and reported low comfort and frequency in performing NFPE assessments (

Table 2. Demographics Including Professional Experience and Expertise of Delphi. Panelists (n = 27).

Variable	n (%)
Age (years)
30–39	15 (55.6)
40–49	8 (29.6)
50 or more	4 (14.4)
Ethnicity
Non-Hispanic	27 (100.0)
Race
White	27 (100.0)
Gender
Male	1 (4.0)
Female	26 (96.0)
Years Working as an RDN
5–15	17 (63.0)
16–25	7 (25.9)
26 or more	3 (11.1)
Years Working as a Bariatric RDN
5–15	20 (74.0)
16 or more	7 (22.0)
Certifications
CSOWM	18 (37.5)
Certificate of Training in Obesity (Adult)	16 (33.3)
Certificate of Training in Obesity (Pediatrics)	6 (12.5)
Meets Criteria for CSOWM	6 (12.5)
Other	1 (2.1)
None	1 (2.1)
Comfort in Performing NFPE
Very Comfortable	2 (7.4)
Somewhat Comfortable	10 (37.0)
Neither Comfortable nor Uncomfortable	6 (22.0)
Somewhat Uncomfortable	4 (14.8)
Very Uncomfortable	3 (11.1)
N/A	2 (7.4)
Frequency of Performing NFPE
>5 Times per Week	4 (14.8)
2–3 Times per Week	5 (18.5)
≤1 Time per Week	18 (66.7)

Abbreviations: CSOWM, Certified Specialist in Obesity and Weight Management; NFPE, Nutrition-Focused Physical Exam; RDN, Registered Dietitian Nutritionist.

).

3.1. Round 1 Overview

The Round 1 survey results, as shown in

Table 3. Round 1 Quantitative Results.

Domain 1: Micronutrients and Components	Usefulness to Practice				Relevance to Practice				Consensus Achieved
	Mean	Standard Deviation	Interquartile Range	Level of Consensus (%)	Mean	Standard Deviation	Interquartile Range	Level of Consensus (%)
Domain 1: Micronutrients	4.96	0.19	0.00	100	5.00	0.00	0.00	100	Yes
Vitamin A	4.63	0.56	1.00	100	4.67	0.55	1.00	100	Yes
Vitamin D	4.86	0.61	0.00	96	4.81	0.63	0.00	96	Yes
Vitamin E	4.30	0.82	1.00	100	4.19	0.88	2.00	100	Yes
Vitamin K	4.33	0.83	1.00	96	4.38	0.85	1.00	96	Yes
Thiamine	4.89	0.32	0.00	100	4.96	0.19	0.00	100	Yes
B12 and Folate/Folic Acid	4.96	0.19	0.00	100	4.93	0.27	0.00	100	Yes
Vitamin C	4.33	0.83	1.00	100	4.04	0.90	2.00	96	Yes
Calcium	4.81	0.62	0.00	96	4.81	0.62	0.00	96	Yes
Iron	4.96	0.19	0.00	100	4.96	0.19	0.00	100	Yes
Zinc	4.59	0.64	1.00	100	4.59	0.64	1.00	100	Yes
Copper	4.62	0.57	1.00	100	4.65	0.56	1.00	100	Yes
Selenium	4.31	0.88	1.00	96	4.12	1.07	2.00	93	Yes
Domain 2: Body Habitus	4.85	0.37	0.00	100	4.88	0.43	0.00	100	Yes
Muscle	4.93	0.27	0.00	100	4.93	0.27	0.00	100	Yes
Fat	4.56	0.70	1.00	100	4.56	0.70	1.00	100	Yes
Bone	4.74	0.53	0.00	100	4.78	0.51	0.00	100	Yes
Hydration	4.93	0.27	0.00	100	4.96	0.19	0.00	100	Yes
Domain 3 Frailty	4.50	0.76	1.00	100	4.50	0.71	1.00	100	Yes
Frailty	4.48	0.70	1.00	100	4.35	0.85	1.00	96	Yes
Domain 4 Surgical Complications	4.84	0.37	0.00	100	4.84	0.37	0.00	100	Yes
GI Bleeding	4.44	0.89	1.00	93	4.59	0.75	1.00	96	Yes
DVT/PE	4.48	0.80	1.00	96	4.56	0.64	1.00	100	Yes
GI Ulcer	4.59	0.75	1.00	96	4.70	0.67	0.00	96	Yes
GI Reflux	4.63	0.74	1.00	96	4.74	0.66	0.00	96	Yes
Skin Infections	4.46	0.81	1.00	96	4.62	0.57	1.00	100	Yes
Anastomotic Leak	4.41	0.93	1.00	93	4.56	0.80	1.00	96	Yes
GI Obstruction	4.52	0.75	1.00	96	4.74	0.45	1.00	100	Yes
GI Fistula	4.46	0.76	1.00	96	4.54	0.76	1.00	96	Yes
Gout	4.50	0.71	1.00	100	4.54	0.65	1.00	100	Yes
Gallstones	4.58	0.76	1.00	96	4.73	0.45	1.00	100	Yes
Kidney Stones	4.42	0.81	1.00	96	4.50	0.76	1.00	96	Yes
Domain 5: GI Complications	4.96	0.20	0.00	100	4.96	0.20	0.00	100	Yes
Inadequate Intake	4.85	0.46	0.00	100	4.85	0.46	0.00	100	Yes
Constipation	4.89	0.32	0.00	100	4.89	0.32	0.00	100	Yes
Diarrhea	4.81	0.40	0.00	100	4.85	0.36	0.00	100	Yes
Dumping Syndrome/PBH	4.85	0.36	0.00	100	4.88	0.33	0.00	100	Yes
Domain 6: Mental Health	4.88	0.33	0.00	100	4.92	0.28	0.00	100	Yes
Depression	4.62	0.64	1.00	100	4.62	0.70	1.00	100	Yes
Transfer Addiction	4.54	0.76	1.00	100	4.50	0.76	1.00	100	Yes
Eating Disorders	4.88	0.33	0.00	100	4.85	0.46	0.00	100	Yes

Abbreviations: DVT, deep vein thrombosis; GI, gastrointestinal; PBH, post-bariatric hypoglycemia; PE, pulmonary embolism.

, demonstrated strong agreement among panelists, as all six domains and 35 components achieved consensus. The lowest component-level agreement was 93 percent, with 85 percent of components reaching 100 percent consensus. On a 1–5 Likert scale, mean scores were high across the board, with a minimum mean of 4.3 for usefulness and 4.0 for relevance. While panelists were not required to answer every item, 96 percent of questions on usefulness and relevance received responses. Despite the micronutrient’s domain containing more components, the highest number of non-responses occurred within the domain of surgical complications.

Open-ended responses were more frequent for the first prompt, which asked panelists to explain their ratings, than for the second, which invited suggestions for additions, deletions, or edits. A few panelists questioned whether RDNs were qualified to assess specific components. However, the survey aimed to evaluate the perceived usefulness and relevance of the information to bariatric nutrition practice, independent of who performs the assessment.

3.2. Rounds 2 & 3 Overview

In the second and third rounds, names and credentials were collected again to track participation. Since all domains and components reached consensus in Round 1, only recommended additions and edits were included in the subsequent surveys. See

Table 4. Round 2 Quantitative Results.

Domain and Component	Usefulness to Practice				Relevance to Practice				Consensus Achieved
	Mean	Standard Deviation	Interquartile Range	Level of Consensus (%)	Mean	Standard Deviation	Interquartile Range	Level of Consensus (%)
Domain 1 Component: Vitamin A Toxicity	4.27	0.96	1.00	96	4.15	1.19	1.00	85	Yes
Domain 1 Component: Vitamin D Toxicity	4.38	0.94	1.00	96	4.30	1.12	1.00	88	Yes
Domain 1 Component: Vitamin E Toxicity	3.77	1.30	2.00	81	3.65	1.32	2.00	81	Yes
Domain 1 Component: Vitamin K Toxicity	3.61	1.32	2.25	76	3.46	1.36	2.25	76	Yes
Domain 4 Component: Hair Loss	4.58	0.64	1.0	100	4.65	0.63	1.0	100	Yes
Domain 4 Component: PBH	4.88	0.33	0.00	100	4.81	0.40	0.00	100	Yes
Domain 5 Component: SIBO	4.65	0.69	0.25	100	4.50	0.76	1.00	100	Yes
Domain 5 Component: Taste Alterations	4.54	0.86	1.00	96	4.62	0.80	0.25	96	Yes
Domain 6 Component: Anxiety	4.46	0.99	1.0	96	4.50	0.91	1.0	96	Yes
Domain 7: SDOH	4.65	0.63	1.0	100	4.65	0.56	1.0	100	Yes
Domain 7: Component: SDOH	4.64	0.64	1.0	100	4.72	0.54	2.0	100	Yes

Abbreviations: SDOH, social determinants of health; SIBO, small intestinal bacterial overgrowth; PBH, post-bariatric hypoglycemia.

for the results of Round 2. Based on panelist feedback, recommended additions from Round 1 included fat-soluble vitamin toxicities (Vitamins A, D, E, and K), hair loss, taste alterations, small intestinal bacterial overgrowth (SIBO), and social determinants of health (SDOH). Vitamin B toxicities were an additional suggestion in Round 2. Suggested edits included identifying nutrient interactions, dividing surgical complications into two categories (early and late), separating dumping syndrome and hypoglycemia, identifying appropriate terminology for dumping syndrome, defining frailty as it relates to BS, and reclassifying gout, gallstones, kidney stones, and hair loss to alternative domains. Panelists had the opportunity to score all newly suggested components for usefulness and relevance and vote on the additional edits.

3.3. Domain 1—Micronutrients

This domain and all components achieved unanimous consensus among panelists. In Table 3, panelists assigned the highest ratings for usefulness and relevance to B Vitamin deficiencies (B12 and folic acid) and Vitamin D, calcium, and iron deficiencies. Conversely, deficiencies in vitamins E, K, C, and selenium, as well as toxicities of B vitamins, received the lowest ratings among the micronutrient components. Panelists commonly perceived Vitamin C as less clinically relevant or less frequently encountered in bariatric populations; however, they did not recommend its exclusion. Panelists recommended including fat-soluble vitamin toxicities, highlighting their importance in BS due to the risk of over-supplementation [48]. Despite all fat-soluble vitamins meeting consensus in Round 2, Vitamin E ratings were low, and Vitamin K minimally met consensus at 76 percent. Comments on the prevalence of B-vitamin toxicities following BS were mixed; however, this added component did meet consensus. Panelists noted that patients often self-prescribe high doses, and some B vitamins are not routinely assessed in standard laboratory panels for this population. Therefore, panelists noted that identifying physical signs is essential. Many RDNs also emphasized the importance of considering interactions between vitamins, minerals, and medications and provided additional suggestions for interactions as outlined in

Table 5. Panelists Approaches and Recommendations for Managing Vitamin, Mineral, and Medication Interactions in Bariatric Surgery [49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76].

Interaction	Recommendation/Practice	Frequency-Participants Who Address Interaction) #/26	Percent (%)	Rationale
Calcium + Iron	Separate calcium by iron for ≥2 h [49]	26	100.0	Calcium inhibits iron absorption [49]
Calcium	Divide calcium doses up to 600 mg throughout the day [50]	26	100.0	Improves calcium absorption [50]
Zinc + Copper	Ensure adequate copper when supplementing zinc (8–15 mg of zinc for every 1 mg of copper) [51]	25	96.2	Prevents copper deficiency [51]
Metformin + B12/Folate	Monitor B12 and folate/folic acid with use of metformin [52]	21	80.8	Metformin may decrease B12 absorption [52]
PPIs + B12	Monitor B12 with use of proton pump inhibitors [53]	22	84.6	Reduced gastric acid may impair B12 absorption [53]
Iron + PPIs	Separate iron from PPIs [53]	16	61.5	Reduced gastric acid may impair iron absorption [53]
Iron + Antacids	Separating iron from antacids [51]	17	65.4	Antacids reduce iron absorption [51]
Diuretics + Potassium	Monitor potassium levels with use of diuretics [54]	14	53.8	Diuretics may alter potassium balance [54]
Non-heme Iron + tannins	Separate non-heme iron (including iron supplements) from tannins (coffee/tea, red wine) [55]	15	57.7	Tannins may inhibit iron absorption [55]
Iron + Vitamin C	Take iron with Vitamin C with iron supplements [55]	26	100.0	Vitamin C improves iron absorption [55]
Fat-Soluble Vitamins + Dietary Fat	Take fat-soluble vitamins with dietary fat [56]	23	88.5	Dietary fat improves fat-soluble vitamin absorption
Iron/Calcium + Levothyroxine	Separate iron and calcium from thyroid medications (levothyroxine) [57]	24	92.3	Iron and calcium reduce thyroid medication absorption [57]
Protein + Iron	Separate milk-based protein drinks from MVI with iron by ≥2 h [58]	NR *	NR	Casein in dairy inhibits non-heme iron absorption [58]
Zinc + Iron/Calcium	Separate zinc supplements from iron and calcium for 2 h when correcting zinc deficiency [59]	NR	NR	Competes for the same transporters, reducing absorption [59]
Thiamine (B1)	Avoid coffee, black tea, chocolate, and alcohol when correcting deficiency [60]	NR	NR	These “foods” inhibit thiamine absorption and utilization [60]
Thiamine + Magnesium	Take magnesium-containing MVI at same time as B1 repletion [61,62]	NR	NR	Magnesium is a cofactor in thiamine activation [61,62]
Calcium Carbonate	Take with food if using calcium carbonate instead of citrate.	NR	NR	Carbonate form requires stomach acid for absorption [63]
Vitamin K + Warfarin	Discuss dietary sources of vitamin K; maintain consistent intake.	NR	NR	Vitamin K affects INR; consistency is key for anticoagulation management [64]
MTHFR Mutation	Use methylated folate and B12 if clinically indicated.	NR	NR	May improve metabolism in patients with reduced MTHFR enzyme activity [65]
Fish Oil	Risks not specified by panelist	NR	NR	There are mixed reports of fish oils effects on bleeding [66,67,68]
Zinc/Copper + Iron/Calcium	Separate trace minerals from calcium and iron.	NR	NR	Prevents absorption interference, especially when correcting deficiencies [69]
Supplement Form	Educate on choosing appropriate supplement forms (calcium citrate, iron sulfate vs. fumarate, or gluconate)	NR	NR	Enhances bioavailability and reduces side effects [70,71,72]
Vitamin A + Retin-A	Avoid combining high-dose oral vitamin A with topical tretinoin.	NR	NR	Risk of vitamin A toxicity [73]
Hair/Skin/Nail Supplements	Review for added zinc or biotin.	NR	NR	Risk of excessive intake or overlapping with prescribed nutrients [74]
Biotin + Lab Tests	Avoid biotin 24 h before thyroid (TSH) or hormone tests.	NR	NR	Biotin interferes with immunoassays and may yield false results [75]
Vitamin E + Elevated Cholesterol	Assess Vitamin E cautiously when cholesterol is elevated	NR	NR	Elevated cholesterol interferes with the absorption of Vitamin E [76]

Abbreviations: B1, thiamine; INR, international normalized ratio; MTHFR, methylenetetrahydrofolate reductase; MVI, multivitamin; NR, not reported; PPIs, proton pump inhibitors; TSH, thyroid stimulating hormone, vs., versus. * Not Recorded

[49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76].

3.4. Domain 2—Body Habitus

All panelists agreed that the body habitus domain and its components are useful and relevant to bariatric practice. Each component received high ratings, with 100 percent consensus achieved for usefulness and relevance. Content analysis revealed a recurring theme that body composition assessments, particularly bioelectrical impedance analysis (BIA), were considered helpful in providing patients with a clearer picture of their weight loss in differentiating between fat and muscle loss. Panelists also noted that these assessments helped educate patients on protein intake, hydration, and supplementation needs. Although some panelists suggested ways to refine the BS-NFPE tool’s signs, symptoms, and assessment methods, they did not recommend any changes to the domain or its components.

3.5. Domain 3—Frailty

Frailty appeared as a domain with a sole component. Panelists reached a 100 percent consensus on the domain’s usefulness and relevance. Several key themes emerged from the panelists’ feedback. Many questioned the practicality or appropriateness of RDNs conducting frailty assessments. Panelists suggested clearly defining frailty in the context of BS and were given the opportunity to propose potential criteria for this population based on 23 frailty assessments cited in the literature [77]. Based on these criteria, more than half of the panelists agreed that a definition of frailty in the bariatric population should include indicators of poor health. These include a high number of comorbidities (n = 20/26, 76.9%), frequent hospitalizations (n = 15/26, 57.7%), abnormal laboratory values such as low iron, low albumin, impaired respiratory volume, and elevated creatinine (n = 15/26, 57.7%), poor nutritional status (n = 22/26, 84.6%), slow walking speed or difficulty ambulating (n = 19/26, 73.1%), poor balance (n = 18/26, 69.2%), recent falls (n = 22/26, 84.6%), impaired cognition or memory (n = 14/26, 53.8%), and unhealthy lifestyle behaviors such as poor diet, inactivity, substance abuse, or inadequate sleep (n = 14/26, 53.8%). Due to using criteria from all frailty assessments identified in the literature, this is a bariatric-adapted frailty conceptualization requiring validation.

3.6. Domain 4—Surgical Complications

The surgical complications domain achieved 100 percent consensus. The lowest-rated components for usefulness in bariatric care were anastomotic leaks, GI fistulas, kidney stones, and GI bleeding; however, these components still received high mean scores of 4.4 to 4.5 on a 5-point Likert scale. Despite some panelists expressing concern that assessing surgical complications is outside the RDN’s scope of practice, many noted the importance of recognizing the physical findings of these complications to make appropriate, timely referrals, especially when emergent care is needed. Although the initially proposed BS-NFPE tool listed hair loss as a sign of nutrient deficiencies, panelists recommended designating it as a standalone component, and all panelists agreed. However, Round 2 feedback suggested that hair loss be placed in a separate domain. In Round 3, panelists voted to include hair loss in a new domain titled “Complications of Rapid Weight Loss” despite rapid weight loss not being the sole contributor. Panelists also suggested dividing complications into early and late categories in Round 1, and nearly 85 percent voted in favor of the separation; however, many found this challenging when asked to do so in the second round, as several components could fall into both categories. Another recommended edit to this domain and its components was to relocate gout, gallstones, and kidney stones to the GI domain; however, in Round 3, this suggestion was overruled by the panelists’ agreement to incorporate these components in the new domain “Complications of Rapid Weight Loss.”

3.7. Domain 5—GI Complications

The GI Complications domain and its components received the highest ratings among all panelists, with 100 percent consensus and all scores exceeding a mean of 4.8 on the 5-point Likert scale. The sentiment, “This is our zone; let us excel,” reflected the panel’s strong support for this domain. Panelists unanimously agreed that this domain was useful and relevant, and most reported that it was comprehensive. SIBO was among the additions and edits proposed for this domain, which was highly rated in terms of usefulness and relevance, meeting 100 percent consensus. Panelists also proposed that taste alterations originally included as a cause of inadequate intake should be considered an independent component. Ratings on taste alterations also demonstrated strong agreement among experts, with a minimum mean of 4.5 on the 5-point Likert scale for usefulness and relevance, and 96 percent met the consensus for both. There was a consistent theme to divide dumping syndrome and PBH into two distinct components and address more contemporary terminology. Separating PBH from dumping syndrome was also well received, with a 92.3 percent agreement. PBH met 100 percent consensus for usefulness and relevance as an independent component. Panelists voted to rename early and late dumping syndrome as rapid gastric emptying and post-bariatric hypoglycemia (PBH), respectively. Although panelists agreed to keep rapid gastric emptying as a GI complication, they voted to move PBH to the domain of surgical complications.

3.8. Domain 6—Mental Health

The Mental Health domain achieved unanimous consensus, with all panelists agreeing on its significance. Assessing eating disorders was rated the highest for usefulness and relevance (mean 4.9 for both) to BS on the 5-point Likert scale. Transfer addiction received the lowest ratings (mean 4.5 for usefulness and relevance), reflecting concerns about the adequacy of available support and debate that persists in the literature. Even though panelists gave transfer addiction lower scores, it still met the consensus criteria. Panelists emphasized the importance of mental health awareness and the RDN’s role in referral rather than direct intervention. On the contrary, addressing mental health concerns was also viewed as a potential opportunity for RDNs, with particular emphasis on their relevance given the extreme lifestyle changes patients experience after BS and RDNs’ frequent contact with patients. The only suggested modifications to the mental health domain were the inclusion of anxiety and the need to address the SDOH. Anxiety was rated with a minimum mean of 4.5 on the Likert scale, and 96 percent of the respondents agreed with its usefulness and relevance to BS. There was also strong support (meeting 100 percent consensus) for including SDOH as an independent component and domain.

4. Discussion

Success following BS is influenced by more than the surgical procedure alone. Nutritional status, both pre-and post-operatively, impacts long-term weight loss success. The commonly used NFPE does not account for all contributors to physical and emotional changes that occur after BS. This limitation could delay the identification of deficiencies and hinder timely interventions. A BS-NFPE tool may improve the early detection of nutritional issues, guide targeted interventions, and enhance patient outcomes.

An initial comprehensive literature review identified six domains and 35 components relevant to the nutritional assessment of patients undergoing BS. These elements were evaluated by a panel of 25 expert bariatric RDNs using a modified Delphi process across three survey rounds. Researchers collected quantitative and qualitative feedback through the Qualtrics platform and invited panelists to justify their ratings and propose edits or additional components. In Round 1, all proposed components reached a consensus. In Round 2, panelists reached a consensus for an additional domain titled SDOH and eight new components proposed by panelists. By Round 3, the authors had incorporated a final domain titled Complications of Rapid Weight Loss and all minor recommended revisions to enhance the clarity and completeness of the final tool. See Figure 1 for a Venn diagram of how all final accepted domains and components overlap (middle oval) with the standard NFPE. The figure illustrates how the standard NFPE is expanded and modified to include the nutrients most specifically affected with bariatric surgery. Additional potential complications of BS that could impact a patient’s nutritional status are also included in the final illustration.

Panelists supported the inclusion of all proposed micronutrients in the BS-NFPE, though some noted that Vitamin C deficiency was less clinically relevant in BS and not frequently encountered. However, it is not typically assessed as outlined in BS guidelines by Mechanick et al. or Parrott et al. [51,78]. More recently, recommended guidelines by Lewis et al. suggest including Vitamin C on the nutrient panel for patients who had the RYGB procedure [79]. Parrott et al. recently suggested that Vitamin C deficiency may be more prevalent than previously recognized, with rates approaching 40 percent among post-operative patients who had the RYGB [80].

The panel also emphasized the importance of monitoring fat-soluble vitamin toxicities, particularly those of Vitamins A and D, due to the risk of over-supplementation. Vitamin A is of particular concern given its teratogenic potential during pregnancy [81,82]. Fertility often increases following BS [82]. Although current guidelines suggest avoiding pregnancy within the first 12–18 months post-surgery, approximately 15 percent of women become pregnant within the first year [83,84]. Therefore, monitoring and educating patients on safe supplementation practices is critical.

The agreement to include B-vitamin toxicities in the BS-NFPE tool is consistent with the emerging literature. There is a risk of neurological effects due to over-supplementation and consumption of vitamin-infused water post-BS, specifically with Vitamins B6 (pyridoxine) and B12 (cobalamin) supplementation [85,86,87,88]. Bossard et al. reported excessive laboratory levels for pyridoxine in up to 40 percent of patients after BS, likely due to pyridoxine in most bariatric vitamins, despite no increase in requirements [87].

Agreement was defined as a rating of ≥3 (neither agree nor disagree) among ≥75% of panelists. To ensure this threshold was not overly permissive, consensus was recalculated using a stricter cutoff of ≥4 (somewhat or strongly agree). Few findings would have changed. Of the 43 final components, only five vitamins and minerals did not meet consensus at the higher cut off. They were vitamin E relevance, vitamin C relevance, selenium relevance, vitamin K usefulness and relevance, and vitamin B toxicity usefulness and relevance.

Panelists identified the need to differentiate PBH from dumping syndrome and suggested using more contemporary terminology for both. Although there was strong agreement to distinguish between the two, consensus on specific terminology was less clear. This indecisiveness is consistent with confusion and lack of consensus in the literature [88]. Early dumping syndrome is generally associated with rapid gastric emptying, which causes fluid to shift from the blood into the small intestine, contributing to low blood volume (hypovolemia), which triggers an autonomic response and presents as vasomotor symptoms [89,90,91]. In contrast, late dumping syndrome, often related to PBH, occurs one to three hours post-meals and unrelated to “dumping” [89]. These hypoglycemic episodes are attributed to alterations in carbohydrate absorption and hormonal changes in incretins and insulin [89]. In agreement with the panelists, PBH appears to be the most accepted terminology in recent publications to replace late dumping syndrome, and terminology for early dumping syndrome does not appear to be as much of an issue [92,93].

Another notable theme that emerged from panelists’ comments was the controversy surrounding the concept of transfer addiction, in which patients who had BS substitute compulsive eating behaviors with other addictive behaviors such as alcohol use, gambling, sex, or substance abuse [94]. While the component reached a consensus for inclusion, panelists correctly identified the ongoing debate in the literature [95]. Some studies have reported increases in alcohol or drug use following BS. For example, a two-year longitudinal study by Conason et al. reported increases in alcohol and drug use post-operatively which the authors suggested may relate to the loss of food as a coping mechanism [96]. Proposed explanations for this increase in use include hormonal shifts and changes in dopamine signaling aligning with the reward deficiency syndrome theory [94]. Similarly, studies by King et al. and Mitchell et al. reported increased rates of alcohol use disorder following RYGB [97,98]. However, findings have not been consistent across studies. Research by Dickhut et al. and Muller et al. found no significant association between preoperative food addiction and the emergence of other addictive behaviors post-operatively, with some studies even noting declines in both [99,100]. Overall, the current evidence remains mixed, and the relationship between BS and the development of other addictive behaviors remains unclear.

The Delphi methodology is particularly suited for guideline development where evidence is lacking in the literature; however, it also has limitations. No universally accepted definition of an “expert” exists, and consensus thresholds vary across studies. Expert selection bias is another concern because the research team identified and recruited panelists through professional connections. Although all had at least five years of experience in BS, and half also held or were eligible to sit for the CSOWM credential, determining true expertise remains challenging. Additionally, the qualitative analysis of open -ended feedback introduces potential researcher bias due to its subjective nature. While maintaining anonymity helped reduce conformity pressure among panelists, the potential for groupthink and acquiescence bias where panelists might select “agree” even if they feel uncertainty remains possible. This could be due to wanting to please the researcher, survey fatigue, not reading questions carefully, or believing agreeing is the “correct” answer. However, multiple rounds in the Delphi method can help mitigate this. The reported low comfort level of some respondents may impact the tool’s perceived validity.

Despite these limitations, several methodological strengths support the credibility of the findings. The iterative Delphi process allowed participants to review group responses and reconsider their ratings across rounds, which may help mitigate the influence of individual uncertainty on final consensus.

Although pre-selection of NFPE components potentially introduced bias, the ability for panelists to propose additions helped mitigate this. While survey fatigue and attrition are common limitations in Delphi studies, this study maintained a high level of engagement, with 25 of 27 original panelists completing all three rounds. Additionally, because the research was conducted online through Qualtrics, this study enabled the inclusion of geographically diverse experts, thereby increasing the generalizability of the findings.

These findings suggest that including physical, emotional and SDOH components into the nutrition exam can be beneficial for successful, long-term weight loss outcomes. This BS-NFPE tool may help RDNs identify issues before they escalate into larger problems, tailor interventions, and refer patients appropriately. Although this study determined expert consensus on components of an expanded and modified BS-NFPE tool, additional evaluation is needed. Further research should assess inter-rater reliability to determine if findings are consistent among dietitians and other practitioners using the tool. Construct validity should also be studied to evaluate whether the tool accurately identifies nutrition-related physical findings in bariatric patients. Additionally, clinical impact testing is warranted to determine whether implementation improves identification of nutritional deficiencies or patient outcomes. Finally, evaluation of the time required to complete the assessment will be important to determine practicality in clinical practice. Future clinical trials could compare the effectiveness of a BS NFPE to the traditional NFPE. Further investigation is warranted to evaluate if the components that did not meet consensus at a rating of 4–5 (Vitamin E, vitamin C, vitamin B toxicity, vitamin K toxicity, and the mineral selenium) should be included in a final validated tool. Additional work is also needed to clarify terminology for PBH, determine the true prevalence of transfer addiction, and the role of SDOH in long-term success. The wide use of this tool by RDNs may improve patient outcomes, minimize long-term adverse outcomes, and promote sustainable weight loss.

5. Conclusions

The final BS-NFPE tool, included in Supplementary File S7, encompasses eight key domains and 43 associated components. This tool comprehensively utilized evidence-based research and expert opinion to provide a guide to identify the multidimensional effects of BS on nutritional status. This newly proposed standardized tool may aid in clinical assessment to improve BS outcomes.