Development and validation testing of a weight management nutrition knowledge questionnaire for adults

The high prevalence and associated medical costs of obesity in the United States create a strong incentive to optimize treatment, commonly delivered through comprehensive lifestyle interventions. Excess energy intake and low physical activity contribute to fat gain, and food-related factors such as high energy density, large portion sizes, greater variety of highly palatable foods, and sugar-sweetened beverages promote excess intake. Lifestyle programs teach these nutrition concepts along with behavior change skills and physical activity, but success is typically evaluated by weight loss, not by whether clients understood key nutrition principles. Prior assessments used general nutrition knowledge tools. The authors hypothesized that teaching and assessing understanding of core nutrition principles would be more useful than memorizing facts, enabling application to novel situations. A focused questionnaire on key dietary principles of weight management would help determine whether nutrition education effectively conveys fundamental concepts. Although knowledge alone does not guarantee behavior change, the knowledge–attitude–behavior model suggests that gains in knowledge are a necessary component for successful behavior change. A literature review found no validated instruments specifically testing dietary principles of weight management, only general nutrition knowledge tools. To address this gap, the authors developed a questionnaire to measure nutrition knowledge as it relates to weight management.

A PubMed search using the terms "nutrition" or "nutritional" and "knowledge" and "questionnaire" or "survey" in the title identified no validated instruments testing dietary principles of weight management; existing validated tools assessed general nutrition knowledge. This gap motivated development of a weight management–specific nutrition knowledge questionnaire.

Design and item development: Approximately 200 items were assembled from existing nutrition questionnaires and newly written items to assess conceptual understanding rather than recall of facts. Content focused on five areas relevant to weight management: energy density, portion/serving size, alcohol and sugar-sweetened beverages, effects of food variety on intake, and reliable nutrition information sources. Items were sourced from instruments and agencies (e.g., Parmenter and Wardle, NHLBI, CDC, Mayo Clinic, USDA), reviewed by a registered dietitian and five external experts, and targeted to a 9th-grade reading level (Flesch-Kincaid). Redundant or overly complex items were removed, yielding 60 items. Face validity: Six experts (PhD/MD nutrition scientists and registered dietitians) reviewed the 60 items for relevance and clarity, recommending modifications and eliminations/additions. Three items were eliminated for being ambiguous or arcane; 57 items remained. Quantitative assessment and samples: 286 adults (≥18 years, proficient in English) from Olmsted County, MN (n=187) and Duval County, FL (n=99) completed the 57-item questionnaire in person. Demographics (including BMI) were self-reported. Psychometric analyses included item difficulty, item discrimination (item–total correlation), inter-item correlation, internal consistency (Cronbach’s alpha), test–retest reliability, construct validity (known-groups), criterion validity (responsiveness to an educational intervention), and convergent validity (associations with demographics). Validity testing: - Construct validity (known-groups): Compared scores of 18 registered dietitians vs 25 information technology (IT) specialists with similar education but expected differences in nutrition knowledge. Independent t-tests assessed overall and section scores; ANCOVA adjusted for demographic differences. Test–retest reliability was assessed by re-administering the questionnaire 2 weeks later to both groups and computing Spearman’s correlation. - Criterion validity (responsiveness): 119 Olmsted County participants attended a three-session (three 1-hour classes over 1–2 weeks) nutrition knowledge intervention adapted from Look AHEAD materials and developed by RD/MD/PhD educators. Didactics used PowerPoint, food models, and Q&A. WMNKQ was administered pre- and post-intervention; paired t-tests evaluated score changes overall and by section; effects were also compared across three interventionists teaching identical materials. - Convergent validity: Using data from 126 participants across counties, ANCOVA tested associations of scores with age groups and education, hypothesizing higher scores in more educated and younger participants. Scoring: For validation, total score was percent correct. A weighted scoring scheme for program evaluation assigns 40% to energy density items, 40% to portion size, and 20% to beverage items; questions on food variety and information sources are scored separately. Statistical analysis: Two-sided tests with alpha=0.05; P values and 95% CIs reported. Item difficulty thresholds: exclude if >90% or <30% correct. Item discrimination threshold: item–total correlation <0.2 flagged for exclusion. Inter-item correlation r>0.9 flagged for redundancy. Internal consistency minimum acceptable Cronbach’s alpha ≥0.7. Tests used: independent t-test, ANCOVA, Spearman’s correlation (test–retest), paired t-test (pre–post).

- Final instrument: 43-item WMNKQ after expert review and psychometric screening. Of the original 60 items, experts removed 3 and modified 41; 57 advanced to quantitative testing. Eighteen items failed item difficulty, discrimination, or inter-item correlation criteria; 4 were retained due to conceptual importance. - Reliability and internal consistency: Cronbach’s alpha = 0.88 (overall). Test–retest reliability Spearman’s ρ = 0.90, P<0.0001 (2-week interval, no intervention). - Construct validity (known-groups): Registered dietitians scored 16% higher than IT specialists (p<0.0001), consistent with expected differences in nutrition knowledge. - Criterion validity (responsiveness to education): Pre- to post-intervention improvement in total score was 11.2% (95% CI 9.8–12.5, p<0.0001) after three one-hour classes. The largest single-item improvement was 56% for an item on energy content of alcoholic beverages (item 34). - Convergent validity: Participants younger than 55 years scored significantly better than those ≥55 years. (Education was hypothesized to correlate positively, but specific results were not reported in the excerpt.) - Item analyses: Six items answered correctly by >90% were excluded. Five items <30% correct: four excluded; one key alcohol-calorie item (item 34) retained and highly responsive to education. Four items with low discrimination were retained due to conceptual importance and responsiveness to education: item 2 (adding low energy density foods reduces calories; +29% post-intervention), item 6 ("buffet effect"; +27%), item 28 (more options increase intake; +40%), and item 34 (alcohol calories; +56%).

The WMNKQ was developed to fill a gap in assessing understanding of nutrition principles specific to weight management. Psychometric testing demonstrates strong internal consistency and excellent test–retest reliability, indicating stable measurement. Known-groups differences between dietitians and IT specialists establish construct validity, while significant pre–post improvements after a targeted educational intervention confirm criterion validity and sensitivity to change. Convergent validity is supported by lower scores in older adults, aligning with expectations. Retention of conceptually important items despite initial low discrimination is justified by their marked responsiveness to education. Collectively, these results indicate the WMNKQ can accurately assess adults’ understanding of key dietary principles (energy density, portion size, beverages, and effects of variety) relevant to weight management, enabling programs to evaluate and refine nutrition education components beyond reliance on weight change alone.

A 43-item Weight Management Nutrition Knowledge Questionnaire (WMNKQ) was developed and validated, showing strong reliability and multiple forms of validity. It provides a practical tool to measure understanding of key nutrition principles for weight management and to evaluate the effectiveness of educational interventions within lifestyle programs.