Diet Quality and Weight Change in Adults Over Time: A Systematic Review of Cohort Studies

Scientific evidence supporting the newly developed one-health labeling tool "Med-Index": an umbrella systematic review on health benefits of mediterranean diet principles and adherence in a planeterranean perspective

BACKGROUND

Med-Index is a one-health front-of-pack (FOP) label, based on Mediterranean diet (MedDiet) principles, developed to summarize information about the nutritional properties and related-health benefits of any food as well as its sustainable production processes, and the associated food company's social responsibility parameters in a new "Planeterranean" perspective. Thus, Med-Index can be adopted in and by any European region and authority as well as worldwide; this is achieved by consumption and cooking of locally available and sourced foods that respect MedDiet principles, both in terms of healthy nutrition and sustainable production. The huge body of scientific evidence about the health benefits of the MedDiet model and principles requires a comprehensive framework to encompass the scientific reliability and robustness of this tool. A systematic review was carried out to examine the association between human health and adherence to MedDiet patterns upon which the "Med-Index" tool was subsequently developed.

METHODS

MEDLINE and PubMed databases were searched for eligible publications from 1990 to April 2023. Systematic literature reviews, with or without meta-analysis, of clinical trials and observational studies were screened by two independent investigators for eligibility, data extraction, and quality assessment. English language and the time interval 1990-2023 were applied. A registry code CRD42023464807 was generated on PROSPERO and approved for this search protocol. The corrected covered area (CCA), calculated to quantify the degree of overlap between reviews, gave a slight overlap (CCA = 4%).

RESULTS

A total of 84 systematic reviews out of 6681 screened records were selected. Eligible reviews included studies with predominantly observational designs (61/84, 72.6%%), of which 26/61 referenced studies of mixed observational and RCT designs, while 23/84 (27.4%) were RCT-only systematic reviews. Seventy-nine different entries were identified for health outcomes, clustered into 10 macro-categories, each reporting a statistically significant association with exposure to the MedDiet. Adherence to MedDiet was found to strongly benefit age-related chronic diseases (21.5%), neurological disorders (19%), and obesity-related metabolic features (12.65), followed by CVDs (11.4%), cancer (10.1%), diabetes (7.5%), liver health (6.3%), inflammation (5%), mortality (5%), and renal health (1.2%). The quality of the studies was moderate to high.

CONCLUSION

In the context of a "Planeterranean" framework and perspective that can be adopted in any European region and worldwide, MedDiet represents a healthy and sustainable lifestyle model, able to prevent several diseases and reduce premature mortality. In addition, the availability of a FOP, such as Med-Index, might foster more conscious food choices among consumers, paying attention both to human and planetary health.

What Is Healthy Eating? Exploring Profiles of Intuitive Eating and Nutritionally Healthy Eating in College Women

PURPOSE

Research suggests that food's nutritional content and the feelings and behaviors associated with eating contribute to overall health, yet these constructs are rarely considered simultaneously. The current cross-sectional study investigated healthy eating profiles in college women that included both nutritional quality and intuitive eating (IE), with IE being an eating style that prioritizes physiological hunger/satiety cues and minimizes dieting and emotional eating.

DESIGN/SETTING/SUBJECTS

Undergraduate women (n=352) completed an online assessment and daily diaries (80% retention).

MEASURES

Nutritionally healthy eating, IE, dieting, body dissatisfaction, disordered eating, and psychological health were examined.

ANALYSIS

Latent profile analysis explored patterns of nutritionally healthy eating and IE, and determined how these patterns related to psychological and eating disorder outcomes.

RESULTS

A four-profile solution emerged: 1) Dieting (high nutritionally healthy eating + intermediate IE), 2) Unhealthy Eating (low nutritionally healthy eating + low IE), 3) Intuitive Eating (moderately high nutritionally healthy eating + high IE), and 4) Non-Dieting (low nutritionally healthy eating + intermediate IE). These profiles significantly differed from one another, such that the Intuitive Eating and Non-Dieting profiles reported lower psychological distress, BMI, and eating disorder symptoms compared to other profiles, while the Dieting and Unhealthy Eating profiles showed the healthiest and poorest nutritional eating, respectively.

CONCLUSION

These findings suggest that IE and nutritionally healthy eating are distinct factors in conceptualizing the eating patterns of college women, and both should be considered when developing interventions. Future research should replicate these findings in larger/more diverse samples and examine eating profiles longitudinally.

Changes in the Global Diet Quality Score, Weight, and Waist Circumference in Mexican Women

BACKGROUND

Evidence on concurrent changes in overall diet quality and weight and waist circumference in women of reproductive age from low- and middle-income countries is limited.

OBJECTIVES

We examined the associations of changes in the Global Diet Quality Score (GDQS) and each GDQS food group with concurrent weight and waist circumference change in Mexican women.

METHODS

We followed prospectively 8967 nonpregnant nonlactating women aged 25-49 y in the Mexican Teachers' Cohort between 2006 and 2008. We assessed diet using an FFQ of the previous year and anthropometric measures were self-reported. Regression models were used to examine 2-y changes in the GDQS and each food group (servings/d) with weight and waist circumference changes within the same period, adjusting for demographic and lifestyle factors.

RESULTS

Compared with those with little change in the GDQS (-2 to 2 points), women with the largest increase in the GDQS (>5 points) had less weight (β: -0.81 kg/2 y; 95% CI: -1.11, -0.51 kg/2 y) and waist circumference gain (β: -1.05 cm/2 y; 95% CI: -1.62, -0.48 cm/2 y); likewise, women with the largest decrease in the GDQS (<-5 points) had more weight (β: 0.36 kg/2 y; 95% CI: 0.06, 0.66 kg/2 y) and waist circumference gain (β: 0.71 cm/2 y; 95% CI: 0.09, 1.32 cm/2 y). Increased intake of dark green leafy vegetables, cruciferous vegetables, deep orange vegetables, citrus fruits, and fish and shellfish was associated with less weight gain. In addition, deep orange vegetables, low fat and high fat dairy, whole grains, and fish were associated with less waist circumference gain within the 2-y period.

CONCLUSIONS

Improvements in diet quality over a 2-y period reflected by an increase in the GDQS and changes in consumption of specific components of the GDQS were associated with less weight and waist circumference gain in Mexican women.

Dietary Changes, Motivators, and Barriers Affecting Diet and Physical Activity among Overweight and Obese: A Mixed Methods Approach

The aims of this study were to examine (1) effects of nutritional guidance and physical activity on dietary habits among overweight and obese after an intervention and one year after follow-up (quantitative study) and (2) barriers and motivators for changes in diet and physical activity (qualitative study). A total of 98 participants with a mean age of 46.8 ± 10.2 years were included and divided into a Training Group (TG) (n = 51) or a Nutritional Guidance and Training Group (NTG) (n = 47). At baseline, after 33 weeks, and one year after the intervention, participants answered a questionnaire. Interviews gave data to elicit motivations and challenges related to diet and exercise. A GLM repeated measures analysis was used to investigate differences and interactions between factors. Participants ate healthier after starting to exercise. After 33 weeks, the NTG ate significantly more vegetables (p = 0.026) and legumes (p < 0.01) than the TG. No significant differences were found one year after follow-up. General health was the most important motivator for changing diet and exercise. Barriers to changing diet were related to work, family, meal size, and participants' internal decisions to change habits. Barriers to exercise were holidays and time constraints. Planning purchases and regular exercise were important factors to achieve and maintain weight loss.

The Relationship of Diet and Physical Activity with Weight Gain and Weight Gain Prevention in Women of Reproductive Age

Reproductive-age women often see increased weight gain, which carries an increased risk of long-term overweight and obesity and adverse maternal and child health outcomes. Supporting women to achieve optimal weight through lifestyle modification (diet and physical activity) is of critical importance to reduce weight gain across key reproductive life-stages (preconception, pregnancy and postpartum). This review comprehensively summarizes the current state of knowledge on the contribution of diet and physical activity to weight gain and weight gain prevention in reproductive-aged women. Suboptimal diets including a higher proportion of discretionary choices or energy intake from fats, added sugars, sweets or processed foods are associated with higher weight gain, whereas increased consumption of core foods including fruits, vegetables and whole grains and engaging in regular physical activity are associated with reduced weight gain in reproductive age women. Diet and physical activity contributing to excessive gestational weight gain are well documented. However, there is limited research assessing diet and physical activity components associated with weight gain during the preconception and postpartum period. This review highlights the need for further research to identify key dietary and physical activity components targeting the critical windows of reproductive life-stages in women to best guide interventions to prevent weight gain.

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.

Longitudinal association between an overall diet quality index and latent profiles of cardiovascular risk factors: results from a population based 13-year follow up cohort study

BACKGROUND

Cardiovascular diseases (CVDs) are associated with an unhealthy lifestyle, including poor diet. Indices reflecting the overall quality of diets are more effective than single food or nutrient-based approaches in clarifying the diet disease relationship. The present study aims to use latent variable modeling to examine the longitudinal joint relationships between the latent profiles of CVDs risk factors and the diet quality index (DQI).

METHODS

A total of 4390 Iranian adults aged 35 and older within the framework of the Isfahan Cohort Study were included in the current secondary analysis. DQI focused on food groups, including fast foods, sweets, vegetables, fruits, fats, and proteins, based on a validated food frequency questionnaire. The score of DQI has a range between 0 (indicating healthy and high diet quality) and 2 (indicating unhealthy and low diet quality). Blood pressure (BP), anthropometric measurements, blood glucose, serum lipids, and high-sensitivity C-Reactive Protein (hs-CRP) were measured according to standard protocols in 2001, 2007, and 2013 to evaluate the profiles of CVDs risk factors. A Bayesian Multidimensional Graded Responses Linear Mixed Model was used for data analysis.

RESULTS

At baseline, the participants' mean ± standard deviation age was 50.09 ± 11.21, and 49.5% of them were male. Three latent profiles of CVDs risk factors were derived: (1) Fit Pre-Metabolic Syndrome (FPMS) profile characterized by normal anthropometric indices and some impaired metabolic risk factors; (2) DysLipoproteinemia Central Obese (DLCO) profile with abdominal obesity and impaired low-density lipoprotein cholesterol as well as other normal risk factors; (3) Impaired Laboratory Inflammatory State (ILIS) profile with impaired high-density lipoprotein cholesterol and hs-CRP and other normal risk factors. In general, higher scores of the extracted latent profiles indicated more impaired function in the related risk factors. After controlling for various potential fixed and time-varying confounding variables, a significant positive longitudinal association was found between FPMS, DLCO, and ILIS profiles and DQI (β (95% CrI): 0.26 (0.03,0.51), 0.14 (0.01,0.27), and 0.24 (0.11,0.38), respectively), demonstrating that lower overall diet quality was associated with more impaired function of the related risk factors.

CONCLUSIONS

More adherence to a healthy quality diet is associated with lower levels of all emerging latent profiles of CVDs risk factors. Increasing the knowledge of the community about the importance of the quality of consumed foods may help to prevent CVDs. It is recommended that further investigations, particularly interventional studies, be conducted to confirm our results.

Association between sustainable dietary patterns and body weight, overweight, and obesity risk in the NutriNet-Santé prospective cohort

BACKGROUND

Improving the sustainability of current food systems may prevent future public health, environmental, and social concerns.

OBJECTIVE

Our objective was to investigate the associations between sustainable dietary patterns, assessed using the Sustainable Diet Index (SDI), and the risk of obesity, overweight, and weight gain in French adults, with a prospective design.

METHODS

In 2014, the SDI was computed among 15,626 participants of the NutriNet-Santé study (of whom 76% were women) using data collected within the BioNutriNet project. The SDI ranges from 4 (lowest sustainability) to 20 points and includes 4 subindexes representing the 4 pillars of a sustainable diet. Longitudinal data of weight and height were collected yearly from 2014 to 2018. We used mixed models to estimate the associations between sex-specific quintiles (Qs) of the SDI and weight change and Cox proportional hazard models with different levels of adjustments to assess the association between sex-specific Qs of the SDI and risk of obesity and overweight (mean follow-up time: 2.8 y).

RESULTS

At baseline, a higher percentage of participants with overweight was observed in the first SDI Q, reflecting the lowest sustainable dietary patterns (Q1), than in Q5 (29.83% compared with 12.71%). Compared with Q5, a slight increase (at the population level) of almost 160 g/y was observed in Q1, whereas weight remained relatively stable among participants in other Qs. In total, 281 incident cases of obesity and 777 cases of overweight were identified during the follow-up. Participants in Q1 had a higher risk of obesity and overweight than participants in Q5 (HR comparing Q1 with Q5: 4.03; 95% CI: 2.42, 6.10; P-trend < 0.001; and HR comparing Q1 with Q5: 1.49; 95% CI: 1.13, 1.95; P-trend < 0.001, respectively).

CONCLUSIONS

The findings support a potential protective role for more sustainable diets to prevent the risk of weight gain, overweight, and obesity.This trial was registered at clinicaltrials.gov as NCT03335644.

Effects of total fat intake on body fatness in adults

BACKGROUND

The ideal proportion of energy from fat in our food and its relation to body weight is not clear. In order to prevent overweight and obesity in the general population, we need to understand the relationship between the proportion of energy from fat and resulting weight and body fatness in the general population.

OBJECTIVES

To assess the effects of proportion of energy intake from fat on measures of body fatness (including body weight, waist circumference, percentage body fat and body mass index) in people not aiming to lose weight, using all appropriate randomised controlled trials (RCTs) of at least six months duration.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, Clinicaltrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) to October 2019. We did not limit the search by language.

SELECTION CRITERIA

Trials fulfilled the following criteria: 1) randomised intervention trial, 2) included adults aged at least 18 years, 3) randomised to a lower fat versus higher fat diet, without the intention to reduce weight in any participants, 4) not multifactorial and 5) assessed a measure of weight or body fatness after at least six months. We duplicated inclusion decisions and resolved disagreement by discussion or referral to a third party.

DATA COLLECTION AND ANALYSIS

We extracted data on the population, intervention, control and outcome measures in duplicate. We extracted measures of body fatness (body weight, BMI, percentage body fat and waist circumference) independently in duplicate at all available time points. We performed random-effects meta-analyses, meta-regression, subgrouping, sensitivity, funnel plot analyses and GRADE assessment.

MAIN RESULTS

We included 37 RCTs (57,079 participants). There is consistent high-quality evidence from RCTs that reducing total fat intake results in small reductions in body fatness; this was seen in almost all included studies and was highly resistant to sensitivity analyses (GRADE high-consistency evidence, not downgraded). The effect of eating less fat (compared with higher fat intake) is a mean body weight reduction of 1.4 kg (95% confidence interval (CI) -1.7 to -1.1 kg, in 53,875 participants from 26 RCTs, I² = 75%). The heterogeneity was explained in subgrouping and meta-regression. These suggested that greater weight loss results from greater fat reductions in people with lower fat intake at baseline, and people with higher body mass index (BMI) at baseline. The size of the effect on weight does not alter over time and is mirrored by reductions in BMI (MD -0.5 kg/m², 95% CI -0.6 to -0.3, 46,539 participants in 14 trials, I² = 21%), waist circumference (MD -0.5 cm, 95% CI -0.7 to -0.2, 16,620 participants in 3 trials; I² = 21%), and percentage body fat (MD -0.3% body fat, 95% CI -0.6 to 0.00, P = 0.05, in 2350 participants in 2 trials; I² = 0%). There was no suggestion of harms associated with low fat diets that might mitigate any benefits on body fatness. The reduction in body weight was reflected in small reductions in LDL (-0.13 mmol/L, 95% CI -0.21 to -0.05), and total cholesterol (-0.23 mmol/L, 95% CI -0.32 to -0.14), with little or no effect on HDL cholesterol (-0.02 mmol/L, 95% CI -0.03 to 0.00), triglycerides (0.01 mmol/L, 95% CI -0.05 to 0.07), systolic (-0.75 mmHg, 95% CI -1.42 to -0.07) or diastolic blood pressure(-0.52 mmHg, 95% CI -0.95 to -0.09), all GRADE high-consistency evidence or quality of life (0.04, 95% CI 0.01 to 0.07, on a scale of 0 to 10, GRADE low-consistency evidence).

AUTHORS' CONCLUSIONS

Trials where participants were randomised to a lower fat intake versus a higher fat intake, but with no intention to reduce weight, showed a consistent, stable but small effect of low fat intake on body fatness: slightly lower weight, BMI, waist circumference and percentage body fat compared with higher fat arms. Greater fat reduction, lower baseline fat intake and higher baseline BMI were all associated with greater reductions in weight. There was no evidence of harm to serum lipids, blood pressure or quality of life, but rather of small benefits or no effect.

Improving diet quality over nine-years is associated with less weight gain in mid-age Australian women: A cohort study

BACKGROUND AND AIMS

Most studies measure baseline diet quality exclusively and hence the impact of longitudinal changes in dietary intake in relation to weight change is not considered. Therefore, this study aimed to examine whether change in diet quality over nine-years was associated with weight change over the same period in mid-age Australian women.

METHODS AND RESULTS

Healthy mid-age (45-49 years) women from the Australian Longitudinal study on Women's Health (ALSWH) were eligible a valid total energy intake (TEI) was reported at baseline (n = 2381), determined using Goldberg cut-offs. Diet quality was measured by the Australian Recommended Food Score (ARFS) using data derived from a validated food frequency questionnaire. Multiple linear regressions were used to evaluate relationships between change in diet quality and weight in mid-age women (n = 1999). Women in the highest tertile of ARFS change improved diet quality [mean ± SD] [7 ± 4 points], while those in the lowest [-9 ±5 points] and middle [-1±2 points] tertiles had worse diet quality at follow-up. Overall, mean weight gain was 2.3 ± 7.2 kg over nine years. Those in the highest tertile of ARFS change gained significantly less weight, compared to the lowest tertile; β = -1.2 kg [95% CI: -2.31, -0.11; p = 0.03] after adjustment for changes in confounders and baseline weight, baseline ARFS, and total energy intake.

CONCLUSIONS

Improving diet quality could be an important strategy for promoting modest weight loss and potentially contribute to preventing weight gain in mid-age women, which is important for metabolic health.

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.

Sugar in mind: Untangling a sweet and sour relationship beyond type 2 diabetes

It is widely recognised that type 2 diabetes (T2D) represents a major disease burden but it is only recently that its role in neurodegeneration has attracted more attention. This research has shown that T2D is associated with impaired cerebral health, cognitive decline and dementia. However, the impact on the brain of progressive metabolic changes associated with the pre-clinical development of the disease is less clear. The aim of this review is to comprehensively summarise how the emergence of risk factors and co-morbid conditions linked to the development of T2D impact cerebral health. Particular attention is directed at characterising how normal but elevated blood glucose levels in individuals without T2D contribute to neurodegenerative processes, and how the main risk factors for T2D including obesity, physical activity and diet modulate these effects. Where available, evidence from the animal and human literature is contrasted, and sex differences in risk and outcomes are highlighted.

Effects of total fat intake on bodyweight in children

BACKGROUND

As part of efforts to prevent childhood overweight and obesity, we need to understand the relationship between total fat intake and body fatness in generally healthy children.

OBJECTIVES

To assess the effects and associations of total fat intake on measures of weight and body fatness in children and young people not aiming to lose weight.

SEARCH METHODS

For this update we revised the previous search strategy and ran it over all years in the Cochrane Library, MEDLINE (Ovid), MEDLINE (PubMed), and Embase (Ovid) (current to 23 May 2017). No language and publication status limits were applied. We searched the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov for ongoing and unpublished studies (5 June 2017).

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in children aged 24 months to 18 years, with or without risk factors for cardiovascular disease, randomised to a lower fat (30% or less of total energy (TE)) versus usual or moderate-fat diet (greater than 30%TE), without the intention to reduce weight, and assessed a measure of weight or body fatness after at least six months. We included prospective cohort studies if they related baseline total fat intake to weight or body fatness at least 12 months later.

DATA COLLECTION AND ANALYSIS

We extracted data on participants, interventions or exposures, controls and outcomes, and trial or cohort quality characteristics, as well as data on potential effect modifiers, and assessed risk of bias for all included studies. We extracted body weight and blood lipid levels outcomes at six months, six to 12 months, one to two years, two to five years and more than five years for RCTs; and for cohort studies, at baseline to one year, one to two years, two to five years, five to 10 years and more than 10 years. We planned to perform random-effects meta-analyses with relevant subgrouping, and sensitivity and funnel plot analyses where data allowed.

MAIN RESULTS

We included 24 studies comprising three parallel-group RCTs (n = 1054 randomised) and 21 prospective analytical cohort studies (about 25,059 children completed). Twenty-three studies were conducted in high-income countries. No meta-analyses were possible, since only one RCT reported the same outcome at each time point range for all outcomes, and cohort studies were too heterogeneous to combine.Effects of dietary counselling to reduce total fat intake from RCTsTwo studies recruited children aged between 4 and 11 years and a third recruited children aged 12 to 13 years. Interventions were combinations of individual and group counselling, and education sessions in clinics, schools and homes, delivered by dieticians, nutritionists, behaviourists or trained, supervised teachers. Concerns about imprecision and poor reporting limited our confidence in our findings. In addition, the inclusion of hypercholesteraemic children in two trials raised concerns about applicability.One study of dietary counselling to lower total fat intake found that the intervention may make little or no difference to weight compared with usual diet at 12 months (mean difference (MD) -0.50 kg, 95% confidence interval (CI) -1.78 to 0.78; n = 620; low-quality evidence) and at three years (MD -0.60 kg, 95% CI -2.39 to 1.19; n = 612; low-quality evidence). Education delivered as a classroom curriculum probably decreased BMI in children at 17 months (MD -1.5 kg/m2, 95% CI -2.45 to -0.55; 1 RCT; n = 191; moderate-quality evidence). The effects were smaller at longer term follow-up (five years: MD 0 kg/m2, 95% CI -0.63 to 0.63; n = 541; seven years; MD -0.10 kg/m2, 95% CI -0.75 to 0.55; n = 576; low-quality evidence).Dietary counselling probably slightly reduced total cholesterol at 12 months compared to controls (MD -0.15 mmol/L, 95% CI -0.24 to -0.06; 1 RCT; n = 618; moderate-quality evidence), but may make little or no difference over longer time periods. Dietary counselling probably slightly decreased low-density lipoprotein (LDL) cholesterol at 12 months (MD -0.12 mmol/L, 95% CI -0.20 to -0.04; 1 RCT; n = 618, moderate-quality evidence) and at five years (MD -0.09, 95% CI -0.17 to -0.01; 1 RCT; n = 623; moderate-quality evidence), compared to controls. Dietary counselling probably made little or no difference to HDL-C at 12 months (MD -0.03 mmol/L, 95% CI -0.08 to 0.02; 1 RCT; n = 618; moderate-quality evidence), and at five years (MD -0.01 mmol/L, 95% CI -0.06 to 0.04; 1 RCT; n = 522; moderate-quality evidence). Likewise, counselling probably made little or no difference to triglycerides in children at 12 months (MD -0.01 mmol/L, 95% CI -0.08 to 0.06; 1 RCT; n = 618; moderate-quality evidence). Lower versus usual or modified fat intake may make little or no difference to height at seven years (MD -0.60 cm, 95% CI -2.06 to 0.86; 1 RCT; n = 577; low-quality evidence).Associations between total fat intake, weight and body fatness from cohort studiesOver half the cohort analyses that reported on primary outcomes suggested that as total fat intake increases, body fatness measures may move in the same direction. However, heterogeneous methods and reporting across cohort studies, and predominantly very low-quality evidence, made it difficult to draw firm conclusions and true relationships may be substantially different.

AUTHORS' CONCLUSIONS

We were unable to reach firm conclusions. Limited evidence from three trials that randomised children to dietary counselling or education to lower total fat intake (30% or less TE) versus usual or modified fat intake, but with no intention to reduce weight, showed small reductions in body mass index, total- and LDL-cholesterol at some time points with lower fat intake compared to controls. There were no consistent effects on weight, high-density lipoprotein (HDL) cholesterol or height. Associations in cohort studies that related total fat intake to later measures of body fatness in children were inconsistent and the quality of this evidence was mostly very low. Most studies were conducted in high-income countries, and may not be applicable in low- and middle-income settings. High-quality, longer-term studies are needed, that include low- and middle-income settings to look at both possible benefits and harms.

Effects of total fat intake on bodyweight in children

BACKGROUND

As part of efforts to prevent childhood overweight and obesity, we need to understand the relationship between total fat intake and body fatness in generally healthy children.

OBJECTIVES

To assess the effects of total fat intake on measures of weight and body fatness in children and young people not aiming to lose weight.

SEARCH METHODS

For this update we revised the previous search strategy and ran it over all years in the Cochrane Library, MEDLINE (Ovid), MEDLINE (PubMed), and Embase (Ovid) (current to 23 May 2017). No language and publication status limits were applied. We searched the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov for ongoing and unpublished studies (5 June 2017).

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in children aged 24 months to 18 years, with or without risk factors for cardiovascular disease, randomised to a lower fat (30% or less of total energy (TE)) versus usual or moderate-fat diet (greater than 30%TE), without the intention to reduce weight, and assessed a measure of weight or body fatness after at least six months. We included prospective analytical cohort studies in these children if they related baseline total fat intake to weight or body fatness at least 12 months later. We duplicated inclusion decisions and resolved disagreement by discussion with other authors.

DATA COLLECTION AND ANALYSIS

We extracted data on participants, interventions or exposures, controls and outcomes, and trial or cohort quality characteristics, as well as data on potential effect modifiers, and assessed risk of bias for all included studies. We extracted outcome data using the following time point ranges, when available: RCTs: baseline to six months, six to 12 months, one to two years, two to five years and more than five years; cohort studies: baseline to one year, one to two years, two to five years, five to 10 years and more than 10 years. We planned to perform random-effects meta-analyses with relevant subgrouping, and sensitivity and funnel plot analyses where data allowed.

MAIN RESULTS

We included 24 studies comprising three parallel-group RCTs (n = 1054 randomised) and 21 prospective analytical cohort studies (about 25,059 children completed). Twenty-three were conducted in high-income countries. No meta-analyses were possible, since only one RCT reported the same outcome at each time point range for all outcomes, and cohort studies were too heterogeneous.For the RCTs, concerns about imprecision and poor reporting limited our confidence in our findings. In addition, the inclusion of hypercholesteraemic children in two trials raised concerns about applicability. Lower versus usual or modified total fat intake may have made little or no difference to weight over a six- to twelve month period (mean difference (MD) -0.50 kg, 95% confidence interval (CI) -1.78 to 0.78; 1 RCT; n = 620; low-quality evidence), nor a two- to five-year period (MD -0.60 kg, 95% CI -2.39 to 1.19; 1 RCT; n = 612; low-quality evidence). Compared to controls, lower total fat intake (30% or less TE) probably decreased BMI in children over a one- to two-year period (MD -1.5 kg/m2, 95% CI -2.45 to -0.55; 1 RCT; n = 191; moderate-quality evidence), with no other differences evident across the other time points (two to five years: MD 0.00 kg/m2, 95% CI -0.63 to 0.63; 1 RCT; n = 541; greater than five years; MD -0.10 kg/m2, 95% CI -0.75 to 0.55; 1 RCT; n = 576; low-quality evidence). Lower fat intake probably slightly reduced total cholesterol over six to 12 months compared to controls (MD -0.15 mmol/L, 95% CI -0.24 to -0.06; 1 RCT; n = 618; moderate-quality evidence), but may make little or no difference over longer time periods. Lower fat intake probably slightly decreased low-density lipoprotein (LDL) cholesterol over six to 12 months (MD -0.12 mmol/L, 95% CI -0.20 to -0.04; 1 RCT; n = 618, moderate-quality evidence) and over two to five years (MD -0.09, 95% CI -0.17 to -0.01; 1 RCT; n = 623; moderate-quality evidence), compared to controls. However, lower total fat intake probably made little or no difference to HDL-C over a six- to 12-month period (MD -0.03 mmol/L, 95% CI -0.08 to 0.02; 1 RCT; n = 618; moderate-quality evidence), nor a two- to five-year period (MD -0.01 mmol/L, 95% CI -0.06 to 0.04; 1 RCT; n = 522; moderate-quality evidence). Likewise, lower total fat intake probably made little or no difference to triglycerides in children over a six- to 12-month period (MD -0.01 mmol/L, 95% CI -0.08 to 0.06; 1 RCT; n = 618; moderate-quality evidence). Lower versus usual or modified fat intake may make little or no difference to height over more than five years (MD -0.60 cm, 95% CI -2.06 to 0.86; 1 RCT; n = 577; low-quality evidence).Over half the cohort analyses that reported on primary outcomes suggested that as total fat intake increases, body fatness measures may move in the same direction. However, heterogeneous methods and reporting across cohort studies, and predominantly very low-quality evidence, made it difficult to draw firm conclusions and true relationships may be substantially different.

AUTHORS' CONCLUSIONS

We were unable to reach firm conclusions. Limited evidence from three trials that randomised children to a lower total fat intake (30% or less TE) versus usual or modified fat intake, but with no intention to reduce weight, showed small reductions in body mass index, total- and LDL-cholesterol at some time points with lower fat intake compared to controls, and no consistent differences in effects on weight, high-density lipoprotein (HDL) cholesterol or height. Associations in cohort studies that related total fat intake to later measures of body fatness in children were inconsistent and the quality of this evidence was mostly very low. Twenty-three out of 24 included studies were conducted in high-income countries, and may not be applicable in low- and middle-income settings. High-quality, longer-term studies are needed, that include low- and middle-income settings and look at both possible benefits and risks.

Diet quality and six-year risk of overweight and obesity among mid-age Australian women who were initially in the healthy weight range

Issue addressed The present study investigated the association between diet quality, measured using the Australian Recommended Food Score (ARFS), and 6-year risk of becoming overweight or obese in mid-age women from the Australian Longitudinal Study of Women's Health (ALSWH). Methods Women (n=1107) aged 47.6-55.8 years who were a healthy weight (body mass index (BMI) between ≤18.5 and <25.0kgm(-2)) at baseline and who reported valid total energy intakes were included in the study. BMI was calculated from self-reported data in 2001 and 2007. ARFS scores were calculated from data collected using the Dietary Questionnaire for Epidemiological Studies Version 2. Logistic regression was used to examine the relationship between ARFS score as a continuous variable and risk of becoming overweight or obese. Results The 6-year incidence of overweight and obesity was 18.5% and 1.1%, respectively. The mean (± s.d.) ARFS (maximum possible 74) among those who remained within the healthy weight range and those who became overweight or obese at follow-up was 35.3±8.1 and 34.3±8.8, respectively. There was no relationship between baseline ARFS and risk of becoming overweight or obese over 6 years. Women who were smokers were more likely to become overweight or obese (odds ratio 1.5; 95% confidence interval 1.11-2.09; P=0.008). Conclusions Poor diet quality was common among mid-age women of a healthy weight in the ALSWH. Higher diet quality was not associated with the risk of overweight or obesity after 6 years, yet smoking status was. So what? Better diet quality alone will not achieve maintenance of a healthy weight, but should be encouraged to improve other health outcomes.

Diet quality is associated with obesity and hypertension in Australian adults: a cross sectional study

BACKGROUND

Poor diet, characterized by a low diet quality score, has been associated with greater prevelence of obesity and hypertension. However, the evidence is inconsistent across diet quality scores and by sex. The aim was to investigate the relationship between diet quality and obesity and hypertension.

METHODS

Adults (n = 4908; age 45.2 ± 0.24 years) were included from the cross-sectional Australian Health Survey 2011-2013. Two 24-h dietary recalls were used to derive the dietary guideline index (DGI) and recommended food score (RFS). Logistic regression investigated relationships between diet quality score and odds ratio of obesity, hypertension and obesity-associated hypertension.

RESULTS

In the highest tertile of DGI, but not RFS, individuals were less likely to be obese (men: OR 0.64, CI: 0.45, 0.92, P-trend = 0.014; women: 0.68, 0.48, 0.96, P-trend = 0.025) and to have central adiposity (men: 0.68, 0.48, 0.97, P-trend = 0.030; women: 0.53, 0.37, 0.77, P-trend = 0.001) compared with the lowest tertile. Men, but not women, in the highest tertile of DGI and RFS were less likely to be hypertensive (DGI: 0.56, 0.37, 0.85, P-trend = 0.006; RFS: 0.62, 0.41, 0.94, P-trend = 0.021) compared with the lowest tertile. In men with obesity, but not normal weight men or women, those in the highest tertile of DGI were less likely to be hypertensive (0.53, 0.36, 0.78, P-trend = 0.001) compared with the highest tertile.

CONCLUSIONS

Higher diet quality, as estimated using DGI, was associated with lower odds ratio of obesity in men and women. Odds ratio of hypertension was lower in men, but not women, with a high diet quality score compared with a low score, while obesity-associated hypertension was only associated with diet quality score in men with obesity. Longitudinal studies are needed to evaluate whether diet quality predicts risk of obesity and hypertension.

Effects of total fat intake on body weight

BACKGROUND

In order to prevent overweight and obesity in the general population we need to understand the relationship between the proportion of energy from fat and resulting weight and body fatness in the general population.

OBJECTIVES

To assess the effects of proportion of energy intake from fat on measures of weight and body fatness (including obesity, waist circumference and body mass index) in people not aiming to lose weight, using all appropriate randomised controlled trials (RCTs) and cohort studies in adults, children and young people

SEARCH METHODS

We searched CENTRAL to March 2014 and MEDLINE, EMBASE and CINAHL to November 2014. We did not limit the search by language. We also checked the references of relevant reviews.

SELECTION CRITERIA

Trials fulfilled the following criteria: 1) randomised intervention trial, 2) included children (aged ≥ 24 months), young people or adults, 3) randomised to a lower fat versus usual or moderate fat diet, without the intention to reduce weight in any participants, 4) not multifactorial and 5) assessed a measure of weight or body fatness after at least six months. We also included cohort studies in children, young people and adults that assessed the proportion of energy from fat at baseline and assessed the relationship with body weight or fatness after at least one year. We duplicated inclusion decisions and resolved disagreement by discussion or referral to a third party.

DATA COLLECTION AND ANALYSIS

We extracted data on the population, intervention, control and outcome measures in duplicate. We extracted measures of weight and body fatness independently in duplicate at all available time points. We performed random-effects meta-analyses, meta-regression, subgrouping, sensitivity and funnel plot analyses.

MAIN RESULTS

We included 32 RCTs (approximately 54,000 participants) and 30 sets of analyses of 25 cohorts. There is consistent evidence from RCTs in adults of a small weight-reducing effect of eating a smaller proportion of energy from fat; this was seen in almost all included studies and was highly resistant to sensitivity analyses. The effect of eating less fat (compared with usual diet) is a mean weight reduction of 1.5 kg (95% confidence interval (CI) -2.0 to -1.1 kg), but greater weight loss results from greater fat reductions. The size of the effect on weight does not alter over time and is mirrored by reductions in body mass index (BMI) (-0.5 kg/m(2), 95% CI -0.7 to -0.3) and waist circumference (-0.3 cm, 95% CI -0.6 to -0.02). Included cohort studies in children and adults most often do not suggest any relationship between total fat intake and later measures of weight, body fatness or change in body fatness. However, there was a suggestion that lower fat intake was associated with smaller increases in weight in middle-aged but not elderly adults, and in change in BMI in the highest validity child cohort.

AUTHORS' CONCLUSIONS

Trials where participants were randomised to a lower fat intake versus usual or moderate fat intake, but with no intention to reduce weight, showed a consistent, stable but small effect of low fat intake on body fatness: slightly lower weight, BMI and waist circumference compared with controls. Greater fat reduction and lower baseline fat intake were both associated with greater reductions in weight. This effect of reducing total fat was not consistently reflected in cohort studies assessing the relationship between total fat intake and later measures of body fatness or change in body fatness in studies of children, young people or adults.