- Title
- The association between diet quality and weight change in young and mid-age women over time
- Creator
- Aljadani, Haya Mohammedali
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2016
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Background: Weight gain is one of the serious health-related issues facing people in all age groups worldwide. Excessive weight gain is linked to increased risk of type 2 diabetes, cardiovascular disease (CVD), some cancers, premature death, and reduced quality of life. Weight gain is a result of an imbalance between total energy intake and the expenditure of energy. Measuring both energy intake and energy expenditure accurately is problematic, especially in large cohorts. Hence, measures of dietary patterns, developed using a priori decisions, is becoming one of the most used methods in epidemiological research. The concept of diet quality is defined as a summary measure of the nutritional quality of the whole diet in comparison to accepted nutrition recommendations. Diet quality tools aim to assess the quality of an individual’s overall eating patterns using a score or index to determine how closely dietary intake aligns with national dietary guidelines and/or recommended nutrient intakes. Evidence shows that diet quality assessments are an acceptable tool which can predict the risk of developing chronic diseases and mortality. However, there is still limited evidence on the relationship between diet quality and some risk factors for health outcomes such as weight change. Aims: This thesis had six main interconnected aims, as follows: 1) To synthesise the best available evidence on the relationship between diet quality indexes or scores and body weight change in prospective studies. ; 2) To compare the predictive association between a number of diet quality indexes with weight change in young women from the Australian Longitudinal Study On Women’s Health (ALSWH) over six years. ; 3) To evaluate the relationship between different diet quality indexes and weight change in a sub-cohort of ‘healthy’ weight young ALSWH women followed for six years. ; 4) To test the relationship between diet quality, measured by the Australian Recommended Food Score (ARFS) and six year weight change in mid-age ALSWH women. ; 5) To examine the association between diet quality (ARFS) in women reporting a healthy weight and valid Total Energy Intake (TEI) and incidence of overweight or obesity in mid-age ALSWH women during six years of follow-up. ; 6) To investigate whether improved diet quality scores (ARFS) over nine years of follow-up are associated with weight gain in mid-age ALSWH women with a valid TEI. Methods and Results: To achieve these aims systematic reviews (in 2011 and 2014) and secondary data analyses of ALSWH data were conducted. Both systematic reviews considered the relationship between diet quality and weight change in adults over time. In 2011, the search was performed on literature published between 1970 to March 2011 in four databases (MEDLINE, CINAHL, EMBASE and Scopus). This review indicated that there was limited and inconsistent evidence on the relationship between diet quality and prospective body weight change in adults, especially among women in cohort studies. The evidence suggests that there was an inverse association between diet quality and weight change longitudinally, but the studies were too heterogeneous for any clear conclusions. A significant number of recent studies have been published in this area, and so the search was re-run in 2014. The 2015 systematic review confirms that higher diet quality is associated with lower body weight gain or lower incidence of overweight or obesity. Further, it found that diet quality tools based on food alone may have a stronger association with weight change in adults than those that rely on or incorporate nutrient sub-scales. However, there is a dearth of studies that use diet quality measures based on food components only. Following the reviews, two analyses were conducted in sub-cohorts of young women from the ALSWH in order to evaluate aims two and three. First, a multivariate linear regression was used to evaluate the predictive relationship between a number of diet quality indexes, with weight change in a sub-cohort of disease-free young women, from the ALSWH who were followed for six years. The three diet quality indexes were the existing ARFS, an adapted version of the Diet Quality Index (DQI) and a newly developed diet quality score named the Fruit and Vegetable Index (FAVI), which have been used to measure diet quality in these women. A second analysis was run on a similar sub-cohort of young women from the ALSWH, but differed in that it included only those women within the healthy weight at baseline. Both studies revealed that young women’s baseline dietary patterns, which contained a greater variety of healthy food such as vegetables, fruit and low fat dairy, legumes and lean protein, are associated with relatively low weight gain compared with those who consumed a less healthy dietary pattern. Three additional analyses were also conducted on data obtained from mid-age women from the ALSWH. The first of these analyses was conducted on a sub-cohort of disease-free women, who were followed for six years. The analyses involved using multivariate linear regression to explore the association between diet quality, defined by the ARFS, and weight change during six years of follow-up. In the second of these analyses data from those women who were identified as having a healthy weight at baseline, had valid TEIs, and were followed for the same six year period, were analysed using multiple linear regression to assess the impact of the ARFS on the risk of becoming overweight or obese over six years of follow-up (i.e. six year incidence of overweight and obesity). From these studies, it was found that higher diet quality, as measured by the ARFS, was not associated with weight gain in mid-age women, nor was it associated with either a decreased or increased risk of becoming overweight or obese. The third of the analyses on mid-aged women from the ALSWH aimed to test whether improvements in diet quality over time can effect weight change in mid-age women during nine years of follow-up. Women were eligible for this analysis if they reported not having any medical conditions at baseline such as type 2 diabetes or heart disease and they reported a valid TEI at baseline. A strong inverse association between change in diet quality measured by the ARFS and weight gain was found over nine years of follow-up. Conclusion and Implication: Taken together, the results show that diet quality is a good predictor of weight change over time in adults in general, although the change is small. In adult women baseline diet quality measured by the ARFS or FAVI is associated with lower weight gain in young women but not in mid-age women. However, the analysis on change in diet quality in the mid-age women revealed that those who improved their ARFS score over time gained the least amount of weight, compared to those who reduced their diet quality over nine years. This research also found that weight gain over time and poor diet quality were common features among both young and mid-age women. The findings from this thesis will help to inform public health nutrition policies, and women more generally, of the importance of consuming a wide variety of healthy foods regularly and aiming to achieve a high diet quality in order to slow the rate of weight gain in those most at risk of gaining weight. Those at greater risk of gaining weight, defined as women who are physically inactive, smokers, in the menopausal transition and less educated than other women at the same age. This thesis has added to the evidence base examining the ability of diet quality scores to predict weight change prospectively. Food based indexes appear to be a useful tool to explore and detect associations with weight change. However for research in the future, well designed studies in different population groups are required to confirm the findings, and to especially examine the role of changes in diet quality over time. The results revealed from this thesis add valuable knowledge to the available literature. They provide justification for ongoing research in this area, specifically on the prevention of weight gain and the role of promoting healthy eating. More intervention studies are particularly required, with the aim of promoting healthy eating, to determine the long-term effects on weight gain and how it may vary for women at different life stages.
- Subject
- women; diet quality; weight
- Identifier
- http://hdl.handle.net/1959.13/1309825
- Identifier
- uon:21948
- Rights
- Copyright 2016 Haya Mohammedali Aljadani
- Language
- eng
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