Mediators of socioeconomic inequalities in dietary behaviours among youth: A systematic review

Children and adolescents with a lower socioeconomic position have poorer dietary behaviours compared to their counterparts with a higher socioeconomic position. A better understanding of the mechanisms behind such socioeconomic inequalities is vital to identify targets for interventions aimed at tackling these inequalities. This systematic review aimed to summarize existing evidence regarding the mediators of socioeconomic differences in dietary behaviours among youth. A systematic literature search of MEDLINE, Embase, PsycINFO, and Web of Science databases yielded 20 eligible studies. The dietary behaviours included in the reviewed studies were the intake of fruit and vegetables, sugar‐sweetened beverages, unhealthy snacks/fast food and breakfast. The consistent mediators of the effects of socioeconomic position on dietary behaviours among youth were: self‐efficacy, food preferences and knowledge at the intrapersonal level; and availability and accessibility of food items at home, food rules and parental modelling at the interpersonal level. Few studies including mediators at the organisational, community or policy levels were found. Our review found several modifiable factors at the intrapersonal and interpersonal levels that could be targeted in interventions aimed at combating inequalities in dietary behaviours among youth. Rigorous studies exploring organisational, community and policy level mediators are warranted.     

Obesity and socioeconomic status in developing countries: a systematic review

We undertook a systematic review of studies assessing the association between socioeconomic status (SES) and measured obesity in low‐ and middle‐income countries (defined by the World Bank as countries with per capita income up to US$12,275) among children, men and women. The evidence on the subject has grown significantly since an earlier influential review was published in 2004. We find that in low‐income countries or in countries with low human development index (HDI), the association between SES and obesity appears to be positive for both men and women: the more affluent and/or those with higher educational attainment tend to be more likely to be obese. However, in middle‐income countries or in countries with medium HDI, the association becomes largely mixed for men and mainly negative for women. This particular shift appears to occur at an even lower level of per capita income than suggested by an influential earlier review. By contrast, obesity in children appears to be predominantly a problem of the rich in low‐ and middle‐income countries.     

The effect of obesity prevention interventions according to socioeconomic position: a systematic review

Obesity prevention is a major public health priority. It is important that all groups benefit from measures to prevent obesity, but we know little about the differential effectiveness of such interventions within particular population subgroups. This review aimed to identify interventions for obesity prevention that evaluated a change in adiposity according to socioeconomic position (SEP) and to determine the effectiveness of these interventions across different socioeconomic groups. A systematic search of published and grey literature was conducted. Studies that described an obesity prevention intervention and reported anthropometric outcomes according to a measure of SEP were included. Evidence was synthesized using narrative analysis. A total of 14 studies were analysed, representing a range of study designs and settings. All studies were from developed countries, with eight conducted among children. Three studies were shown to have no effect on anthropometric outcomes and were not further analysed. Interventions shown to be ineffective in lower SEP participants were primarily based on information provision directed at individual behaviour change. Studies that were shown to be effective in lower SEP participants primarily included community‐based strategies or policies aimed at structural changes to the environment. Interventions targeting individual‐level behaviour change may be less successful in lower SEP populations. It is essential that our efforts to prevent obesity do not leave behind the most disadvantaged members of society.     

The weight of US residence among immigrants: a systematic review

As the number of immigrants in the USA continues to rise, it becomes increasingly important to understand how their health differs from native‐born individuals. Obesity is a public health concern and a component of health that may differ and change in important ways in immigrants. This research synthesizes the current literature on the relationship between immigrant duration of residence in the USA and body weight. Five databases from the health and social sciences were searched for all pertinent publications. Fifteen articles met inclusion criteria, 14 of which reported a significant, positive relationship between body mass index and duration of residence in the USA (all P‐values <0.10). Two studies reported a threshold effect of weight gain after 10 years of US residence, and another study reported that body mass index peaks after 21 years of duration for men and after 15 years for women. The results of this review suggest that weight gain prevention programmes would be beneficial for many immigrants within the first decade of residence in the USA. Prevention efforts may be more successful if nativity and acculturation are considered in addition to race/ethnicity. Future research is needed to identify the specific mechanisms through which living in the USA may adversely affect health outcomes.     

The association between childcare arrangements and risk of overweight and obesity in childhood: a systematic review

Over 80% of preschool‐aged children experience non‐parental childcare. Childcare type has the potential to influence weight outcomes, but its impact on childhood overweight/obesity is not well established. This review aims to (i) systematically evaluate the effects of childcare type on childhood overweight/obesity risk and (ii) investigate the impact of childcare intensity and age at commencement. Five electronic databases were searched for observational studies quantifying an association between childcare type ≤5 years and weight outcomes <18 years. Twenty‐four studies were included (n = 127,529 children). Thirteen studies reported increased risk of overweight/obesity in children attending informal care (n = 9) or centre care (n = 4) vs. parental care. Seven studies reported decreased risk of overweight/obesity for children in centre vs. ‘non‐centre’ care (parental and informal). Four studies reported no association between informal or centre care and overweight/obesity. Early (<3 years) informal care, especially by a relative, was associated with increased risk of overweight/obesity. Higher intensity childcare, especially when commenced early (<1 year), increased overweight/obesity risk. Later (≥3 years) centre care was associated with decreased risk of overweight/obesity. Early informal care, earlier commencement age and higher intensity represent a risk for childhood obesity. Exploration of the obesogenic aspects of these contexts is essential to inform preventative measures.     

Associations between socioeconomic position and correlates of sedentary behaviour among youth: a systematic review

Existing research evidence indicates that children and adolescents of parents with a low socioeconomic position spend more time on sedentary behaviour than their counterparts. However, the mechanisms driving these differences remain poorly understood. The main aim of this systematic review was to summarize the evidence regarding the association between socioeconomic position and correlates of sedentary behaviour among youth (0–18 years) from developed countries. The literature search was conducted using MEDLINE, Embase, CINAHL and PsycINFO. A total of 37 studies were included. All but three studies examined screen‐based sedentary behaviours only. Methodological quality ranged from low to moderate. Education was the most commonly used indicator of socioeconomic position, followed by income. Socioeconomic position was inversely related to the presence of a TV in the child's bedroom, parental modelling for TV viewing, parental co‐viewing and eating meals in front of the TV. We found no/indeterminate evidence for an association between socioeconomic position and rules and regulations about screen time. The findings suggest possible factors that could be targeted in future intervention studies to decrease screen‐based sedentary behaviour in lower socioeconomic groups in particular.     

A systematic review of the effectiveness of whole‐of‐community interventions by socioeconomic position

Whole‐of‐community (WOC) interventions have led to modest reductions in population weight gain. Whether they exhibit differential effectiveness by socioeconomic position (SEP) remains unknown. We aimed to summarize evidence of differential effectiveness of WOC interventions by SEP. Electronic databases and grey literature were searched to identify studies that evaluated the effectiveness of a WOC intervention on behavioural change measures, energy balance behaviours and/or anthropometric outcomes according to any measure of SEP. Interventions were assessed for the following characteristics: structural changes to the environment, number of settings the intervention acted in, presence of community engagement and whether equity was considered in its design. Ten studies were included. Nine reported a greater or equal effect among low SEP groups compared with high SEP groups. These studies commonly featured interventions that incorporated structural changes to the environment, acted across more than three settings and/or employed community engagement. Conclusions did not change when excluding low‐quality studies (n = 4). WOC interventions represent an effective and equitable approach for the reduction of population weight. Structural components, a larger number of settings and community engagement were common in equitable WOC interventions and should be considered in the design of future WOC interventions.     

Disability pension,employment and obesity status: a systematic review

Disability pensions incur huge societal costs in many countries. In Sweden, the three greatest drivers of such productivity losses are musculo‐skeletal, circulatory and psychiatric disorders, all closely associated with weight status. We identified 16 studies investigating the body mass index (BMI)–disability pension relation. In cross‐sectional studies, a significantly greater proportion of obese compared with normal weight subjects were disability pensioners. In longitudinal studies, a J‐shaped relation with BMI was generally found in both men and women of various ages. Different definitions of obesity status complicated interpretation, as several studies mixed the underweight and normal weight, which appear to have different disability pension risks. In middle‐aged men, relative risks were elevated for circulatory causes only for the overweight and obese, while associations for mental disorders were similar in the underweight and overweight but much higher in the obese. In both sexes, monotonic increases and decreases were seen for circulatory and respiratory causes respectively. In intervention studies, reduced disability pension incidence and increased gainful employment were reported after surgery. In summary, BMI was significantly associated with disability pension, but the direction of causality may vary with underlying cause. Interventions had positive productivity effects in the morbidly obese, but whether this holds for the overweight remains to be proven.     

Selected eating behaviours and excess body weight: a systematic review

The relationship between obesity and the intake of macronutrients and specific foods is uncertain. Thus, there is growing interest in some eating behaviours because they may reflect the joint effect of several foods and nutrients and, thus, increase the likelihood of finding a link to obesity. This study examined the association between selected eating behaviours and excess weight in the general population throughout a systematic review of publications written in English, Spanish or Portuguese identified in a PubMed search up to 31 December 2010. We included 153 articles, 73 of which have been published since 2008. Only 30 studies had a prospective design; of these, 15 adjusted for sociodemographic variables, physical activity and energy or food intake. Moreover, definitions of eating behaviours varied substantially across studies. We found only small or inconsistent evidence of a relationship between excess weight and skipping breakfast, daily eating frequency, snacking, irregular meals, eating away from home, consumption of fast food, takeaway food intake, consumption of large food portions, eating until full and eating quickly. In conclusion, this review highlights the difficulty in measuring human behaviour, and suggests that a more systematic approach is needed for capturing the effects of eating behaviours on body weight.     

Developmental coordination disorder and overweight and obesity in children: a systematic review

Children with developmental coordination disorder (DCD) find themselves less competent than typically developing children with regard to their physical abilities and often experience failure. They are therefore likely to avoid physical activity. Physical inactivity is considered an important risk factor for developing overweight and obesity. The aim of this study is to assess the association between DCD and overweight and obesity in children and whether this association is influenced by age and/or gender. Six electronic databases were systematically searched. Titles and abstracts were screened for relevance. Remaining studies were subjected to full paper review. The quality of the included articles was assessed and relevant data were extracted for comparison. The search yielded 273 results. Twenty‐one studies, based on 10 cohorts, were included. Participants' ages ranged from 4 to 14 years. In all cohorts, children with DCD had higher body mass index scores, larger waist circumference and greater percentage body fat compared with controls. Seven studies assessed the effect of gender and four studies provided information on the effect of age. Children with DCD seem to be at greater risk for overweight and obesity. This risk may be higher for boys and seems to increase with age and with the severity of motor impairment.     

Relationship of fruit and vegetable intake with adiposity: a systematic review

Fruit and vegetable (FV) intake has been proposed to protect against obesity. The purpose of this paper was to assess the FV consumption to adiposity relationship. Twenty‐three publications were included. Inclusion criteria: longitudinal or experimental designs; FV intake tested in relation to adiposity; child, adolescent or adult participants; published in English‐language peer‐reviewed journals. Exclusion criteria: dietary pattern and cross‐sectional designs; participants with health concerns. Experimental studies found increased FV consumption (in conjunction with other behaviours) contributed to reduced adiposity among overweight or obese adults, but no association was shown among children. Longitudinal studies among overweight adults found greater F and/or V consumption was associated with slower weight gain, but only half of child longitudinal studies found a significant inverse association. Limitations in methods prevented a thorough examination of the role of increased FV intake alone or mechanisms of effect. An inverse relationship between FV intake and adiposity among overweight adults appears weak; this relationship among children is unclear. Research needs to clarify the nature of, and mechanisms for, the effects of FV consumption on adiposity. Whether increases in FV intake in isolation from lower caloric intake or increased physical activity will result in declines or slower growth in adiposity remains unclear.     

Dairy consumption and overweight and obesity: a systematic review of prospective cohort studies

A comprehensive literature search was undertaken to examine the relationship between dairy consumption and overweight/obesity in prospective cohort studies. A literature search from 1980 through to April 2010 was conducted. Nineteen cohort studies met all the inclusion criteria and were included in the systematic review. Of the 19 cohort studies, 10 were among children and adolescents (aged 2 to 14 years, n = 53 to 12 829, follow‐up 8 months to 10 years) and nine among adults (aged 18 to 75 years, n = 248 to 42 696, follow‐up 2 years to 12 years). A range of dairy food exposure measures were used. Eight studies (three out of 10 studies involving children and five out of nine studies involving adults) showed a protective association against increasing weight gain (measured in various ways); one reported a significant protective association only among men who were initially overweight; seven reported no effect; one reported an increased risk (among children), and two reported both a decreased and increased risk, depending on the dairy food type. The evidence from prospective cohort studies for a protective effect of dairy consumption on risk of overweight and obesity is suggestive but not consistent, making firm conclusions difficult.     

The effect of obesity on polycystic ovary syndrome: a systematic review and meta‐analysis

While many women with polycystic ovary syndrome (PCOS) are overweight, obese or centrally obese, the effect of excess weight on the outcomes of PCOS is inconsistent. The review aimed to assess the effects of overweight, obesity and central obesity on the reproductive, metabolic and psychological features of PCOS. MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL) and PSYCINFO were searched for studies reporting outcomes according to body mass index categories or body fat distribution. Data were presented as mean difference or risk ratio (95% confidence interval). This review included 30 eligible studies. Overweight or obese women with PCOS had decreased sex hormone‐binding globulin (SHBG), increased total testosterone, free androgen index, hirsutism, fasting glucose, fasting insulin, homeostatic model assessment‐insulin resistance index and worsened lipid profile. Obesity significantly worsened all metabolic and reproductive outcomes measured except for hirsutism when compared to normal weight women with PCOS. Overweight women had no differences in total testosterone, hirsutism, total‐cholesterol and low‐density lipoprotein‐cholesterol compared to normal weight women and no differences in SHBG and total testosterone compared to obese women. Central obesity was associated with higher fasting insulin levels. These results suggest that prevention and treatment of obesity is important for the management of PCOS.     

Pre‐pregnancy and pregnancy obesity and neurodevelopmental outcomes in offspring: a systematic review

Maternal obesity in pregnancy is associated with a number of adverse outcomes for mother and her offspring both perinatally and later in life. This includes recent evidence that suggests that obesity in pregnancy may be associated with central nervous system problems in the foetus and newborn. Here, we systematically review studies that have explored associations between maternal overweight and obesity in pregnancy and cognitive, behavioural and emotional problems in offspring. The 12 studies eligible for this review examined a wide range of outcomes across the lifespan and eight provided evidence of a link. These data suggest that the offspring of obese pregnancies may be at increased risk of cognitive problems and symptoms of attention deficit hyperactivity disorder in childhood, eating disorders in adolescence and psychotic disorders in adulthood. Given the limitations of existing data, these findings warrant further study, particularly in light of the current worldwide obesity epidemic.     

Association of eating while television viewing and overweight/obesity among children and adolescents: a systematic review and meta‐analysis of observational studies

The objective of this systematic review and meta‐analysis was to examine the association between eating while television viewing (TVV) and overweight or obesity in children (<18 years). A systematic search of PubMed, Scopus, Web of science, PreQuest and Embase was conducted up to April 2017; pooled odds ratio (OR) and 95% confidence intervals (CI) were calculated using a random effects model. Of 4,357 articles identified, 20 observational studies met inclusion criteria (n = 84,825) and 8 of these 20 (n = 41,617) reported OR. Eating while TVV was positively associated with obesity‐related anthropometric measurements in 15 studies (75%). The meta‐analysis revealed that eating while TVV was positively associated with being overweight (OR = 1.28; 95% CI: 1.17, 1.39). Subgroup analyses showed similar positive associations in both girls and boys, as well as in children who ate dinner while TVV. There was no evidence of publication bias. The present systematic review and meta‐analysis suggests that eating while TVV could be a risk factor for being overweight or obese in childhood and adolescents.     

Unhealthy diets,obesity and time discounting: a systematic literature review and network analysis

There is an increasing policy commitment to address the avoidable burdens of unhealthy diet, overweight and obesity. However, to design effective policies, it is important to understand why people make unhealthy dietary choices. Research from behavioural economics suggests a critical role for time discounting, which describes how people's value of a reward, such as better health, decreases with delay to its receipt. We systematically reviewed the literature on the relationship of time discounting with unhealthy diets, overweight and obesity in Web of Science and PubMed. We identified 41 studies that met our inclusion criteria as they examined the association between time discount rates and (i) unhealthy food consumption; (ii) overweight and (iii) response to dietary and weight loss interventions. Nineteen out of 25 cross‐sectional studies found time discount rates positively associated with overweight, obesity and unhealthy diets. Experimental studies indicated that lower time discounting was associated with greater weight loss. Findings varied by how time discount rates were measured; stronger results were observed for food than monetary‐based measurements. Network co‐citation analysis revealed a concentration of research in nutrition journals. Overall, there is moderate evidence that high time discounting is a significant risk factor for unhealthy diets, overweight and obesity and may serve as an important target for intervention. © 2016 The Authors Obesity Reviews published by John Wiley & Sons Ltd on behalf of International Association for the Study of Obesity (IASO)     

Trends in overweight and obese adults in Malaysia (1996–2009): a systematic review

Like other nations experiencing rapid industrialization, urbanization and a nutrition transition, there is concern in Malaysia of a possible escalation in the prevalence of overweight and obesity. In 1996, the National Health and Morbidity Survey reported a 16.6% and 4.4% prevalence of overweight and obesity, respectively. In the following decade, there have been several national and community surveys on overweight and obesity in Malaysia. The objective of this systematic review is to describe the trend from 1996 to 2009 in the prevalence of overweight and obesity in adults in Malaysia nationally and by gender, age and race. Results indicate that there has been a small rise in overweight adults in the years 1996, 2003 and 2006 (20.7%, 26.7% and 29.1%) and a much more dramatic increase in obesity in 1996, 2003, 2004 and 2006 (5.5%, 12.2%, 12.3% and 14.0%). Evidence showed a greater risk for overweight and obesity among women compared with men. Based on the highest‐quality studies, overweight and obesity levels were highest among adults 40–59 years old. Overweight levels were highest among Indians, followed by Malays, Chinese and Aboriginals, with less consistency across studies on the order of risk or obesity by ethnicity.     

The association between obesity and academic performance in youth: a systematic review

Previous studies have found that obesity could influence academic performance. The aim of this study was to systematically review the scientific evidence on the association between obesity and academic performance in school children. A systematic review of English articles was undertaken by using databases PubMed/Medline, ERIC, LILACS, SciELO and Web of Science. Cross‐sectional and longitudinal studies examining the association between obesity and academic performance in children and adolescents, published between January 1990 and December 2016, were included. Risk of bias was assessed by using Strengthening the Reporting of Observational Studies in Epidemiology. Thirty‐four studies (23 cross‐sectional and 11 longitudinal) matched all inclusion criteria and were included. Seven studies were classified as low risk of bias, 23 as medium risk and four as high risk. After controlling for covariates such as socio‐economic status, parental education and physical activity, the association between obesity and academic performance becomes uncertain for most of the studies (55.9%). Therefore, at present, there is insufficient evidence to support a direct link between obesity and poor academic performance in school age children. In order to clarify this issue, we need more longitudinal studies with adequate sample sizes and that control for potential confounders.     

Chromium supplementation in overweight and obesity: a systematic review and meta‐analysis of randomized clinical trials

The increased prevalence of obesity has made the use of dietary supplements as weight reducing agents highly popular, but their efficacy has not been proven. One such supplement is chromium. The purpose of this review was to evaluate the evidence for or against the efficacy of chromium supplementation in overweight and obese individuals. Electronic searches were conducted in Medline, Embase, Amed and The Cochrane Library. The bibliographies of located articles were also searched. No age, gender or language restrictions were imposed. The reporting quality of identified randomized clinical trials (RCTs) was assessed using a methodological checklist adapted from the Consolidated Standard of Reporting Trials Statement and Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines. Thirty‐nine trials were identified and 20 were included. There were variations in reporting quality of included studies. A meta‐analysis of 11 studies showed a statistically significant difference in weight loss favouring chromium over placebo (mean difference (MD): ?0.50 kg; 95% confidence interval (CI): ?0.97, ?0.03). There was a high statistical heterogeneity. Adverse events included watery stools, vertigo, headaches and urticaria. The evidence from available RCTs shows that chromium supplementation generates statistically significant reductions in body weight. The magnitude of the effect is small, and the clinical relevance is uncertain. Future trials should last at least 16 weeks and greater uniformity in the measuring and assessment tools for body composition is recommended.