HNUT 40270 – PROJECT
Assessment 1
Experimental design and analysis plan
Table of Contents
Title ......................................................................................................................................................... 1
Introduction ............................................................................................................................................ 1
Research Questions:........................................................................................................................... 1
Design ..................................................................................................................................................... 2
REFERENCES ............................................................................................................................................ 3
Mark Costa
20202630
19/02/2023
Word count: 465
Title
The association between the plant-based dietary index and obesity: a cross-sectional
analysis from the National Adult Nutrition Survey (NANS) in Ireland.
Introduction
In Ireland, a significant increase in body mass index (BMI), waist circumference (WC) and
waist-to-hip ratio (WHR) was observed from 1990 to 2011 (1). The prevalence of overweight
and obesity in Irish adults has been reported to be 36% and 15%, respectively. Chronic
diseases such as cardiovascular disease (CVD), hypertension and type 2 diabetes (T2D) have
been suggested to be ameliorated with significant reductions in BMI(2).
Several meta-analyses have concluded that adherence to a plant-based diet (PBD) has
favourable outcomes on weight reduction(3-5). A validated plant-based dietary index (PDI) was
used to investigate the association between adherence to PBD with several outcomes,
including mortality (6, 7), T2D (8, 9), CVD (10, 11) and cancer (12, 13). Currently, studies investigating
PDI with obesity are scarce, and conflicting results have emerged with studies reporting
positive associations(14), negative associations(15,
16)
and no associations(17,
18)
with
anthropometric outcomes relating to obesity.
To this day, the association between PDI and obesity has not been explored within the Irish
population. Hence, the aim of this study was to investigate the relationship between
adherence to a PBD and obesity within the National Adults Nutrition Survey (NANS) cohort.
Research Questions:
RQ 1: What is the relationship between adherence to a plant-based diet and anthropometric
measures of obesity as measured by BMI, WC and WHR in the Irish population?
RQ 2: Does this association differ between males and females in the Irish population?
1
Design
This analytical cross-sectional study will include 700 participants aged 18-84 years from the
NANS dataset compiled between 2008-2010. Food diaries were used to collect habitual food
and beverage intake. Non-stretch tape and Tanita body scale analysers were used to measure,
WC and weight, respectively(19).
The procedure to construct the indices were previously elucidated and a similar protocol will
be carried out in this study (6, 8-10). A total of 15 food groups (FG) will be used, 9 of which are
predominantly plant-based (PPB) and 6 are predominantly animal-based (PAB). Each FG will
be split into quintiles of energy consumption (Kcal) and participants will be assigned to a
quintile according to the amount of energy consumed within the respective FG. Each quintile
corresponds with a score. The lowest quintile has a score of 1, while the highest quintile has
a score of 5 for PPB FGs. Reverse scoring will be applied for PAB FGs. Scores from each FG will
be summed, obtaining a minimum score of 15 and a maximum score of 75. The higher the
score, the more adherence to a PBD. Participants will be further categorised into tertiles
according to their PDI scores.
A Kolmogorov-Smirnov test will be used to assess normality distributions(20). PDI scores will
be associated with BMI (kg/m2), WC (cm) and WHR using Pearson correlation followed by a
simple linear regression. Univariate general linear model will be used to identify differences
between genders while controlling for age, smoking and recreational activity levels. A oneway analysis of variance (ANOVA) will be used to compare continuous variables across tertiles,
followed by post-HOC where necessary. Significant differences will be considered at P-values
< 0.05.
2
REFERENCES
1.
Boylan EA, McNulty BA, Walton J, Flynn A, Nugent AP, Gibney MJ. The prevalence and trends
in overweight and obesity in Irish adults between 1990 and 2011. Public Health Nutrition.
2014;17(11):2389-97.
2.
Kearns K, Dee A, Fitzgerald AP, Doherty E, Perry IJ. Chronic disease burden associated with
overweight and obesity in Ireland: the effects of a small BMI reduction at population level. BMC Public
Health. 2014;14(1):143.
3.
Barnard ND, Levin SM, Yokoyama Y. A Systematic Review and Meta-Analysis of Changes in
Body Weight in Clinical Trials of Vegetarian Diets. Journal of the Academy of Nutrition and Dietetics.
2015;115(6):954-69.
4.
Demirci Ü, Kaptanoğlu A. Adherence to Vegetarian Diet and Weight Loss: A Meta-Analysis:
Adherence to Vegetarian Diet and Weight Loss: A Meta-Analysis. Progress in Nutrition.
2022;24(2):e2022036.
5.
Tran E, Dale HF, Jensen C, Lied GA. Effects of Plant-Based Diets on Weight Status: A Systematic
Review. Diabetes Metab Syndr Obes. 2020;13:3433-48.
6.
Martínez-González MA, Sánchez-Tainta A, Corella D, Salas-Salvadó J, Ros E, Arós F, et al. A
provegetarian food pattern and reduction in total mortality in the Prevención con Dieta Mediterránea
(PREDIMED) study. Am J Clin Nutr. 2014;100 Suppl 1:320s-8s.
7.
Kim J, Kim H, Giovannucci EL. Plant-based diet quality and the risk of total and disease-specific
mortality: A population-based prospective study. Clinical Nutrition. 2021;40(12):5718-25.
8.
Chen Z, Drouin-Chartier JP, Li Y, Baden MY, Manson JE, Willett WC, et al. Changes in Plant-
Based Diet Indices and Subsequent Risk of Type 2 Diabetes in Women and Men: Three U.S. Prospective
Cohorts. Diabetes Care. 2021;44(3):663-71.
9.
Satija A, Bhupathiraju SN, Rimm EB, Spiegelman D, Chiuve SE, Borgi L, et al. Plant-Based
Dietary Patterns and Incidence of Type 2 Diabetes in US Men and Women: Results from Three
Prospective Cohort Studies. PLoS Med. 2016;13(6):e1002039.
10.
Satija A, Bhupathiraju SN, Spiegelman D, Chiuve SE, Manson JE, Willett W, et al. Healthful and
Unhealthful Plant-Based Diets and the Risk of Coronary Heart Disease in U.S. Adults. Journal of the
American College of Cardiology. 2017;70(4):411-22.
11.
Kim H, Caulfield LE, Garcia‐Larsen V, Steffen LM, Coresh J, Rebholz CM. Plant‐Based Diets Are
Associated With a Lower Risk of Incident Cardiovascular Disease, Cardiovascular Disease Mortality,
3
and All‐Cause Mortality in a General Population of Middle‐Aged Adults. Journal of the American Heart
Association. 2019;8(16):e012865.
12.
Kim J, Boushey CJ, Wilkens LR, Haiman CA, Le Marchand L, Park S-Y. Plant-based dietary
patterns defined by a priori indices and colorectal cancer risk by sex and race/ethnicity: the
Multiethnic Cohort Study. BMC Medicine. 2022;20(1):430.
13.
Rigi S, Mousavi SM, Benisi-Kohansal S, Azadbakht L, Esmaillzadeh A. The association between
plant-based dietary patterns and risk of breast cancer: a case–control study. Scientific Reports.
2021;11(1):3391.
14.
Waterplas J, Versele V, D'Hondt E, Lefevre J, Mertens E, Charlier R, et al. A 10‐year longitudinal
study on the associations between changes in plant‐based diet indices, anthropometric parameters
and blood lipids in a Flemish adult population. Nutrition & dietetics. 2020;77(2):196-203.
15.
Wang YB, Shivappa N, Hébert JR, Page AJ, Gill TK, Melaku YA. Association between Dietary
Inflammatory Index, Dietary Patterns, Plant-Based Dietary Index and the Risk of Obesity. Nutrients.
2021;13(5):1536.
16.
Chen B, Zeng J, Qin M, Xu W, Zhang Z, Li X, et al. The Association Between Plant-Based Diet
Indices and Obesity and Metabolic Diseases in Chinese Adults: Longitudinal Analyses From the China
Health and Nutrition Survey. Frontiers in nutrition (Lausanne). 2022;9:881901-.
17.
Jung S, Park S. Positive association of unhealthy plant-based diets with the incidence of
abdominal obesity in Korea: a comparison of baseline, most recent, and cumulative average diets.
Epidemiology and health. 2022;44:e2022063-e.
18.
Asoudeh F, Mousavi SM, Keshteli AH, Hasani-Ranjbar S, Larijani B, Esmaillzadeh A, et al. The
association of plant-based dietary pattern with general and abdominal obesity: a large cross-sectional
study. Journal of diabetes and metabolic disorders. 2023.
19.
National Adult Nutrition Survey (NANS) methodology [Internet]. Irish Universities Nutrition
Alliance.
2011
[cited
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Available
from:
https://irp-
cdn.multiscreensite.com/46a7ad27/files/uploaded/The%20National%20Adult%20Nutrition%20Surv
ey%20%28NANS%29%20%282008-2010%29.pdf.
20.
Mishra P, Pandey CM, Singh U, Gupta A, Sahu C, Keshri A. Descriptive statistics and normality
tests for statistical data. Ann Card Anaesth. 2019;22(1):67-72.
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