Prospective associations between diet quality and body mass index in disadvantaged women: the Resilience for Eating and Activity Despite Inequality (READI) study

Change analysis for intermediate disease markers in nutritional epidemiology: a causal inference perspective

BACKGROUND

Several approaches are commonly used to estimate the effect of diet on changes of various intermediate disease markers in prospective studies, including "change-score analysis", "concurrent change-change analysis" and "lagged change-change analysis". Although empirical evidence suggests that concurrent change-change analysis is most robust, consistent, and biologically plausible, in-depth dissection and comparison of these approaches from a causal inference perspective is lacking. We intend to explicitly elucidate and compare the underlying causal model, causal estimand and interpretation of these approaches, intuitively illustrate it with directed acyclic graph (DAG), and further clarify strengths and limitations of the recommended concurrent change-change analysis through simulations.

METHODS

Causal model and DAG are deployed to clarify the causal estimand and interpretation of each approach theoretically. Monte Carlo simulation is used to explore the performance of distinct approaches under different extents of time-invariant heterogeneity and the performance of concurrent change-change analysis when its causal identification assumptions are violated.

RESULTS

Concurrent change-change analysis targets the contemporaneous effect of exposure on outcome (measured at the same survey wave), which is more relevant and plausible in studying the associations of diet and intermediate biomarkers in prospective studies, while change-score analysis and lagged change-change analysis target the effect of exposure on outcome after one-period timespan (typically several years). Concurrent change-change analysis always yields unbiased estimates even with severe unobserved time-invariant confounding, while the other two approaches are always biased even without time-invariant heterogeneity. However, concurrent change-change analysis produces almost linearly increasing estimation bias with violation of its causal identification assumptions becoming more serious.

CONCLUSIONS

Concurrent change-change analysis might be the most superior method in studying the diet and intermediate biomarkers in prospective studies, which targets the most plausible estimand and circumvents the bias from unobserved individual heterogeneity. Importantly, careful examination of the vital identification assumptions behind it should be underscored before applying this promising method.

Diet Quality and Body Mass Index Over 20 Years in the Multiethnic Cohort

BACKGROUND

With increasing rates of overweight and obesity and disparities by ethnicity, it is important to understand the role of diet in ameliorating this health problem.

OBJECTIVE

This study examined the relation of diet quality as measured by the Healthy Eating Index 2015 with body mass index (BMI; calculated as kg/m2) and obesity among participants of the Multiethnic Cohort (MEC) in cross-sectional analyses at 3 time points (T-1, T-2, and T-3) over 20 years.

DESIGN

In a subset of 1,860 MEC participants, 3 cross-sectional analyses at cohort entry (1993 to 1996, T-1) and follow-ups in 2003 to 2008 (T-2) and 2013 to 2016 (T-3) were performed.

PARTICIPANTS/SETTING

The cohort consists of African American, Native Hawaiian, Japanese American, Latino, and White adults in Hawaii and California; mean age was 48 years at T-1.

MAIN OUTCOME MEASURE

BMI and weight status in relation to diet quality were measured.

STATISTICAL ANALYSIS

Linear and multinomial logistic regressions were applied to analyze the relation of diet quality with BMI and obesity, while adjusting for known confounders.

RESULTS

Healthy Eating Index 2015 increased by 6.1 and 5.1 units for men and women, respectively, from T-1 to T-3; the respective values for BMI were 1.5 and 2.4. Diet quality was inversely associated with BMI across time: BMI was lower by -0.47, -0.72, and -0.92 units for every 10-point increase in Healthy Eating Index 2015 scores at T-1, T-2, and T-3, respectively (P < .0001 for all). During the 20 years, the association was consistently high among Japanese American participants (-0.79, -0.87, and -1.02) and weakest in African American cohort members (-0.34, -0.37, and -0.40). Higher diet quality was related to lower odds of having obesity at all 3 time points; prevalence odds ratios were 0.72, 0.57, and 0.60.

CONCLUSIONS

These findings suggest that consuming a high-quality diet is related to lower BMI and rates of overweight and obesity but with the strongest association at an older age. To understand the ethnic differences, investigations of dietary habits and behaviors and/or fat distribution patterns will be needed in the future.

Family Psychosocial Assets, Child Behavioral Regulation, and Obesity

BACKGROUND AND OBJECTIVES

Little attention has been given to the study of early childhood factors that protect against the development of obesity and severe obesity. We investigated whether exposure to familial psychosocial assets and risks in infancy (1-15 months) and early childhood (24-54 months) and child behavioral regulation in early childhood predict longitudinal change in BMI (2 to 15 years).

METHODS

Participants included 1077 predominantly non-Hispanic, White, English-speaking mother-child dyads from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development dataset. Cumulative familial asset and risk indices were created using measures (eg, maternal parenting sensitivity, poverty) from 2 developmental periods (1-15 months, 24-54 months). A child behavioral regulation index was created on the basis of behavioral tasks and parent reports. Previously published BMI trajectories (nonoverweight [40th percentile], nonoverweight [70th percentile], overweight/obese, severely obese) were used as the outcome.

RESULTS

All indices predicted membership in the overweight/obese trajectory; however, when entered into the same model, only familial assets continued to reduce the odds of membership in this trajectory. Familial assets and child behavioral regulation independently reduced the odds of membership in the severely obese trajectory. Furthermore, child behavioral regulation and familial assets buffered the negative effects of familial risk on BMI trajectory membership.

CONCLUSIONS

Early exposure to familial assets and child behavioral regulation may have long-term protective effects on weight gain over early exposure to some familial risk factors (eg, poverty); thus, these indices may help foster obesity resilience.

Higher Global Diet Quality Score Is Associated with Less 4-Year Weight Gain in US Women

BACKGROUND

We have developed a simple and globally applicable tool, the Global Diet Quality Score (GDQS), to measure diet quality.

OBJECTIVES

To test the utility of the GDQS, we examined the associations of the GDQS with weight change and risk of obesity in US women.

METHODS

Health, lifestyle, and diet information were collected from women (n = 68,336) in the Nurses' Health Study II (aged 27-44 y in 1991) through repeated questionnaires (1991-2015). The GDQS has 25 food groups (maximum = 49 points) and scoring higher points reflects a healthier diet. The association between GDQS change in 4-y intervals and concurrent weight change was computed with linear models adjusted for confounders.

RESULTS

Mean ± SD weight gain across 4-y periods was 1.68 ± 6.26 kg. A >5-point improvement in GDQS was associated with -1.13 kg (95% CI: -1.19, -0.77 kg) weight gain compared with a score change of <±2 points. For each 5-point increase, weight gain was 0.83 kg less for age <50 y compared with 0.71 kg less for age ≥50 y (P-interaction < 0.05). A >5-point score decrease was associated with 1.13 kg (95% CI: 1.04, 1.22 kg) more weight gain in women aged <50 y and 0.81 kg more (95% CI: 0.63, 0.98 kg) in women aged ≥50 y. Compared with little change in score, obesity RR was 0.77 (95% CI: 0.74, 0.81) for a >5-point increase and 1.32 (95% CI: 1.26, 1.37) for a >5-point decrease. Risk of obesity did not differ by age. Compared with other diet quality scores, the Alternate Healthy Eating Index-2010 had somewhat stronger associations than the GDQS (P < 0.05) but the GDQS had stronger associations than the Minimum Dietary Diversity for Women score (P < 0.05).

CONCLUSIONS

Improvement of diet quality as measured by the GDQS was associated with less weight gain and risk of obesity in US women. The association was stronger for women aged <50 y. Associations similar in direction and magnitude were observed between the GDQS and obesity across age groups.

Association between Dietary Inflammatory Index, Dietary Patterns, Plant-Based Dietary Index and the Risk of Obesity

Evidence on the association between various dietary constructs and obesity risk is limited. This study aims to investigate the longitudinal relationship between different diet indices and dietary patterns with the risk of obesity. Non-obese participants (n = 787) in the North West Adelaide Health Study were followed from 2010 to 2015. The dietary inflammatory index (DII^®), plant-based dietary index (PDI) and factor-derived dietary pattern scores were computed based on food frequency questionnaire data. We found the incidence of obesity was 7.62% at the 5-year follow up. In the adjusted model, results from multivariable log-binomial logistic regression showed that a prudent dietary pattern (RR_Q5 vs. _Q1 = 0.38; 95% CI: 0.15–0.96), healthy PDI (RR = 0.31; 95% CI: 0.12–0.77) and overall PDI (RR = 0.56; 95% CI: 0.23–1.33) were inversely associated with obesity risk. Conversely, the DII (RR = 1.59; 95% CI: 0.72–3.50), a Western dietary pattern (RR = 2.16; 95% CI: 0.76–6.08) and unhealthy PDI (RR = 1.94; 95% CI: 0.81–4.66) were associated with increased risk of obesity. Based on the cubic spline analysis, the association between an unhealthy PDI or diet quality with the risk of obesity was non-linear. In conclusion, an anti-inflammatory diet, healthy diet or consumption of healthy plant-based foods were all associated with a lower risk of developing obesity.

Diet Quality and Its Effect on Weight Gain Prevention in Young Adults: A Narrative Review

Global environmental and societal changes have resulted in an increased consumption of energy-dense foods contributing to escalating obesity prevalence, with most rapid weight gain occurring in young adults. Diet is one major modifiable factor contributing to escalating obesity prevalence. Understanding overall diet quality of populations at high risk for weight gain and obesity development, including young adults, provides evidence of dietary intakes, dietary patterns, and associated behaviors, to inform the development of targeted interventions aimed at the prevention of weight gain. This narrative review synthesizes the current evidence of the association between diet quality and weight gain in young adults. Overall, there is a consistent direction of association between improved diet quality and reduced weight gain in adults. This demonstrates the potential of small improvements in diet quality over time as a probable contributor to minimizing weight gain in young adults. Future research evaluating environmental nutrition policies with associated change in diet quality and prospective weight change in population-based studies is warranted to determine their longer-term impact in improving overall diet quality as one strategy to halt escalating obesity prevalence rates.

Individual, social-environmental and physical-environmental correlates of diet quality in young adults aged 18-30 years

Many young adults eat a poor-quality diet. However, understanding of the social-ecological correlates of diet quality in young adults is limited. The aim of the present study was to examine the correlates of diet quality in a cohort of young Australian adults. Data from the cross-sectional Measuring EAting in everyday Life Study were used. Young adults (n = 625; 18-30 years; 73% female) were included if they provided dietary data over three or four non-consecutive days using 'FoodNow', a real-time food diary smartphone application. Diet quality was estimated using the 2013 Dietary Guidelines Index (DGI). Thirty correlates from three levels of the social-ecological framework were collected using an online questionnaire: individual (e.g., self-efficacy), social-environmental (e.g., social support) and physical-environmental (e.g., living situation). Linear regression analyses were used to examine associations between correlates and DGI. Six individual-level correlates were associated with DGI: perceived time scarcity (b = -0.664, CI: 1.160, -0.168), food insecurity (b = -0.962, CI: 1.746, -0.178), self-efficacy (b = 0.230, CI: 0.137, 0.323), being born in Australia (b = -3.165, CI: 5.521, -0.808), being employed in non-trade roles (b = -4.578, CI: 8.903, -0.252) and preparing a meals with vegetables daily (b = 4.576, CI: 1.652, 7.500). No social-environmental or physical-environmental correlates were associated with DGI. Overall, this study showed that young adults had a higher diet quality if they had higher self-efficacy, perceived themselves to be less time scarce and less food insecure, were born in Australia, were employed in non-trade roles and prepared a meal with vegetables daily. Healthy eating policies and interventions in young adults may benefit from targeting individual-level correlates.

Diet Quality Indices Used in Australian and New Zealand Adults: A Systematic Review and Critical Appraisal

Distilling the complexity of overall diet into a simple measure or summative score by data reduction methods has become a common practice in nutritional epidemiology. Recent reviews on diet quality indices (DQI) have highlighted the importance of sound construction criteria and validation. The aim of this current review was to identify and critically appraise all DQI used within Australian and New Zealand adult populations. Twenty-five existing DQI were identified by electronic searching in Medline and hand searching of reference lists. DQI were constructed based on the respective national dietary guidelines and condition-specific recommendations. For preferable features of DQI, six captured the dimensions of adequacy, moderation and balance; five had a nested structure; 12 consisted of foods, food groups and nutrients; 11 used metric scoring systems and most of those with metric scales used normative cutoff points. Food frequency questionnaires, either alone or with other methods, were the most common dietary assessment method used in 20 DQI. For evaluation of DQI, construct validity and relative validity are reported. Based on our critical appraisal, Dietary Guideline Index (DGI), Dietary Guideline Index-2013 (DGI-2013), Total Diet Score (TDS), Healthy Eating Index for Australian Adults-2013 (HEIFA-2013), and Aussie-Diet Quality Index (Aussie-DQI) were the preferred DQI used in Australian adults according to dimension, indicator selection, scoring criteria and evaluation. Further work is needed to enhance the construction of all Australian and New Zealand DQI, especially in terms of dimension and structure, for alignment with recommended construction criteria.

Adherence to National Food Guide Recommendations: Can It Slow the Obesity Epidemic? A Systematic Review

PURPOSE OF REVIEW

Dietary guidelines (DG) have the objective to promote healthy diet and prevent chronic diseases. In order to evaluate if this purpose is being achieved, we systematically reviewed studies that associated adherence to DG with obesity.

RECENT FINDINGS

We identified 2012 articles published in the last 5 years, and 38 remained in the final sample. The majority of studies demonstrated a negative association between adherence to DG and obesity. Studies with positive or no association presented mutual characteristics, such as populations composed only by children or adolescents, and dietary intake or dietary adherence assessed through non-validated or weak methods. Adherence to DG seems to be a protective factor for obesity in adults, but this relationship is not so clear for children and adolescents. To improve the quality of dietary intake results, studies must utilize appropriate methods to answer their questions with less biased estimate of dietary intake.

Frequency and variety of usual intakes of healthy foods, fruit, and vegetables predicts lower 6-year weight gain in young women

BACKGROUND/OBJECTIVES

We previously demonstrated that fruit and vegetable consumption, was associated with less weight gain over 6 years in young women for all body mass index (BMI) categories. This study evaluated the relationship between diet quality and 6-year weight change, in Australian women initially in the healthy weight range (≥18.5 BMI <25 kg/m²) at baseline.

SUBJECTS/METHODS

A total of 4083 young women (27-31 years) in the healthy weight range (≥18.5 BMI <25 kg/m²) enroled in the Australian Longitudinal study on Women's Health (ALSWH) were analysed. Diet quality was measured by the Australian Recommended Food Score (ARFS) and the Fruit and Vegetable Index (FAVI) using dietary data derived from a validated food frequency questionnaire. Weight change was calculated as the difference between baseline and 6-year follow-up weight (kg). Multiple linear regression models were used to analyse the association between baseline ARFS and FAVI and 6-year weight change.

RESULTS

At baseline, mean diet quality was low for both indices [ARFS (maximum 72) = 29.9 and FAVI (maximum 333) = 94.2] and women gained 3.7 kg of weight during 6 years of follow-up. Regression modelling revealed that every one point increase over 6 years in either the ARFS or FAVI score was associated with statistically significantly less weight gain over 6 years, although the amount was small (33 and 12 g, respectively).

CONCLUSIONS

Higher diet quality predicts lower prospective weight gain in young women however, further research is needed over a longer follow-up period and in diverse population groups.