Viewpoints of adolescents with overweight and obesity attending lifestyle obesity treatment interventions : a qualitative systematic review

Background Current UK guidance recommends that adolescents with obesity attend a family-based multi-component obesity intervention. However, these programmes suffer from low recruitment and high rates of attrition. Understanding the views of adolescents is necessary for developing future interventions. The aim of this systematic review was to synthesise and explore the views of adolescents who have attended an obesity intervention. Methods Published literature was identified by searching six databases. Studies of adolescents (12-17 years) who attended an obesity intervention were examined. Only studies that collected and analysed data qualitatively were included. Full-texts were analysed using thematic synthesis. Results Twenty-eight studies were included. Thirty-five analytical themes were developed that were broadly divided into seven domains. Key themes included ensuring adolescents receive a ‘tailored intervention’ that involves ‘active engagement’. Support from professionals, family and peers was valued highly. Adolescents expressed ‘prior fears of attending interventions’ and wanted ‘longer-term support’. ‘Enjoyment of sport and physical activity’ was evident and adolescents were strongly motivated by improving body image and social desirability. Discussion Considering the views of adolescents attending obesity interventions may help to inform policy makers in the development of future interventions. This may lead to an improvement in recruitment and attrition rates

Diet, physical activity, and behavioural interventions for the treatment of overweight or obesity in preschool children up to the age of 6 years (Review)

Background Child overweight and obesity has increased globally, and can be associated with short‐ and long‐term health consequences. Objectives To assess the effects of diet, physical activity, and behavioural interventions for the treatment of overweight or obesity in preschool children up to the age of 6 years. Search methods We performed a systematic literature search in the databases Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL, and LILACS, as well as in the trial registers ClinicalTrials.gov and ICTRP Search Portal. We also checked references of identified trials and systematic reviews. We applied no language restrictions. The date of the last search was March 2015 for all databases. Selection criteria We selected randomised controlled trials (RCTs) of diet, physical activity, and behavioural interventions for treating overweight or obesity in preschool children aged 0 to 6 years. Data collection and analysis Two review authors independently assessed risk of bias, evaluated the overall quality of the evidence using the GRADE instrument, and extracted data following the Cochrane Handbook for Systematic Reviews of Interventions. We contacted trial authors for additional information. Main results We included 7 RCTs with a total of 923 participants: 529 randomised to an intervention and 394 to a comparator. The number of participants per trial ranged from 18 to 475. Six trials were parallel RCTs, and one was a cluster RCT. Two trials were three‐arm trials, each comparing two interventions with a control group. The interventions and comparators in the trials varied. We categorised the comparisons into two groups: multicomponent interventions and dietary interventions. The overall quality of the evidence was low or very low, and six trials had a high risk of bias on individual 'Risk of bias' criteria. The children in the included trials were followed up for between six months and three years. In trials comparing a multicomponent intervention with usual care, enhanced usual care, or information control, we found a greater reduction in body mass index (BMI) z score in the intervention groups at the end of the intervention (6 to 12 months): mean difference (MD) ‐0.3 units (95% confidence interval (CI) ‐0.4 to ‐0.2); P < 0.00001; 210 participants; 4 trials; low‐quality evidence, at 12 to 18 months' follow‐up: MD ‐0.4 units (95% CI ‐0.6 to ‐0.2); P = 0.0001; 202 participants; 4 trials; low‐quality evidence, and at 2 years' follow‐up: MD ‐0.3 units (95% CI ‐0.4 to ‐0.1); 96 participants; 1 trial; low‐quality evidence. One trial stated that no adverse events were reported; the other trials did not report on adverse events. Three trials reported health‐related quality of life and found improvements in some, but not all, aspects. Other outcomes, such as behaviour change and parent‐child relationship, were inconsistently measured. One three‐arm trial of very low‐quality evidence comparing two types of diet with control found that both the dairy‐rich diet (BMI z score change MD ‐0.1 units (95% CI ‐0.11 to ‐0.09); P < 0.0001; 59 participants) and energy‐restricted diet (BMI z score change MD ‐0.1 units (95% CI ‐0.11 to ‐0.09); P < 0.0001; 57 participants) resulted in greater reduction in BMI than the comparator at the end of the intervention period, but only the dairy‐rich diet maintained this at 36 months' follow‐up (BMI z score change in MD ‐0.7 units (95% CI ‐0.71 to ‐0.69); P < 0.0001; 52 participants). The energy‐restricted diet had a worse BMI outcome than control at this follow‐up (BMI z score change MD 0.1 units (95% CI 0.09 to 0.11); P < 0.0001; 47 participants). There was no substantial difference in mean daily energy expenditure between groups. Health‐related quality of life, adverse effects, participant views, and parenting were not measured. No trial reported on all‐cause mortality, morbidity, or socioeconomic effects. All results should be interpreted cautiously due to their low quality and heterogeneous interventions and comparators. Authors' conclusions Muticomponent interventions appear to be an effective treatment option for overweight or obese preschool children up to the age of 6 years. However, the current evidence is limited, and most trials had a high risk of bias. Most trials did not measure adverse events. We have identified four ongoing trials that we will include in future updates of this review. The role of dietary interventions is more equivocal, with one trial suggesting that dairy interventions may be effective in the longer term, but not energy‐restricted diets. This trial also had a high risk of bias

Parent-only interventions for childhood overweight or obesity in children aged 5 to 11 years

Background: Child and adolescent overweight and obesity have increased globally, and are associated with short- and long-term health consequences.Objectives: To assess the efficacy of diet, physical activity and behavioural interventions delivered to parents only for the treatment of overweight and obesity in children aged 5 to 11 years.Search methods: We performed a systematic literature search of databases including the Cochrane Library,MEDLINE, EMBASE, PsycINFO, CINAHL and LILACS as well trial registers.We checked references of identified trials and systematic reviews.We applied no language restrictions. The date of the last search was March 2015 for all databases.Selection criteria: We selected randomised controlled trials (RCTs) of diet, physical activity and behavioural interventions delivered to parents only for treating overweight or obesity in children aged 5 to 11 years.Data collection and analysis: Two review authors independently assessed trials for risk of bias and evaluated overall study quality using the GRADE instrument. Where necessary, we contacted authors for additional information.Main results: We included 20 RCTs, including 3057 participants. The number of participants ranged per trial between 15 and 645. Follow-up ranged between 24 weeks and two years. Eighteen trials were parallel RCTs and two were cluster RCTs. Twelve RCTs had two comparisons and eight RCTs had three comparisons. The interventions varied widely; the duration, content, delivery and follow-up of the interventions were heterogeneous. The comparators also differed. This review categorised the comparisons into four groups: parent-only versus parent-child, parent-only versus waiting list controls, parent-only versus minimal contact interventions and parent-only versus other parent-only interventions. Trial quality was generally low with a large proportion of trials rated as high risk of bias on individual risk of bias criteria. In trials comparing a parent-only intervention with a parent-child intervention, the body mass index (BMI) z score change showed a mean difference (MD) at the longest follow-up period (10 to 24 months) of -0.04 (95% confidence interval (CI) -0.15 to 0.08); P = 0.56; 267 participants; 3 trials; low quality evidence. In trials comparing a parent-only intervention with a waiting list control, the BMI z score change in favour of the parent-only intervention at the longest follow-up period (10-12 months) had an MD of -0.10 (95% CI -0.19 to -0.01); P = 0.04; 136 participants; 2 trials; low quality evidence. BMI z score change of parent-only interventions when compared with minimal contact control interventions at the longest follow-up period (9 to 12 months) showed an MD of 0.01 (95% CI -0.07 to 0.09); P = 0.81; 165 participants; 1 trial; low quality evidence. There were few similarities between interventions and comparators across the included trials in the parent-only intervention versus other parent-only interventions and we did not pool these data. Generally, these trials did not show substantial differences between their respective parent-only groups on BMI outcomes. Other outcomes such as behavioural measures, parent-child relationships and health-related quality of life were reported inconsistently. Adverse effects of the interventions were generally not reported, two trials stated that there were no serious adverse effects. No trials reported on all-cause mortality, morbidity or socioeconomic effects. All results need to be interpreted cautiously because of their low quality, the heterogeneous interventions and comparators, and the high rates of non-completion.Authors’ conclusions: Parent-only interventions may be an effective treatment option for overweight or obese children aged 5 to 11 years when compared with waiting list controls. Parent-only interventions had similar effects compared with parent-child interventions and compared with those with minimal contact controls. However, the evidence is at present limited; some of the trials had a high risk of bias with loss to follow-up being a particular issue and there was a lack of evidence for several important outcomes. The systematic review has identified 10 ongoing trials that have a parent-only arm, which will contribute to future updates. These trials will improve the robustness of the analyses by type of comparator, and may permit subgroup analysis by intervention component and the setting. Trial reports should provide adequate details about the interventions to be replicated by others. There is a need to conduct and report cost effectiveness analyses in future trials in order to establish whether parent-only interventions are more cost-effective than parent-child interventions

Whole grain cereals for the primary or secondary prevention of cardiovascular disease

Background: There is evidence from observational studies that whole grains can have a beneficial effect on risk for cardiovascular disease (CVD). Earlier versions of this review found mainly short-term intervention studies. There are now longer-term randomised controlled trials (RCTs) available. This is an update and expansion of the original review conducted in 2007. Objectives:The aim of this systematic review was to assess the effect of whole grain foods or diets on total mortality, cardiovascular events, and cardiovascular risk factors (blood lipids, blood pressure) in healthy people or people who have established cardiovascular disease or related risk factors, using all eligible RCTs. Search methods: We searched CENTRAL (Issue 8, 2016) in the Cochrane Library, MEDLINE (1946 to 31 August 2016), Embase (1980 to week 35 2016), and CINAHL Plus (1937 to 31 August 2016) on 31 August 2016. We also searched ClinicalTrials.gov on 5 July 2017 and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) on 6 July 2017. We checked reference lists of relevant articles and applied no language restrictions. Selection criteria: We selected RCTs assessing the effects of whole grain foods or diets containing whole grains compared to foods or diets with a similar composition, over a minimum of 12 weeks, on cardiovascular disease and related risk factors. Eligible for inclusion were healthy adults, those at increased risk of CVD, or those previously diagnosed with CVD. Data collection and analysis: Two review authors independently selected studies. Data were extracted and quality-checked by one review author and checked by a second review author. A second review author checked the analyses. We assessed treatment effect using mean difference in a fixed-effect model and heterogeneity using the I2 statistic and the Chi2 test of heterogeneity. We assessed the overall quality of evidence using GRADE with GRADEpro software. Main results: We included nine RCTs randomising a total of 1414 participants (age range 24 to 70; mean age 45 to 59, where reported) to whole grain versus lower whole grain or refined grain control groups. We found no studies that reported the effect of whole grain diets on total cardiovascular mortality or cardiovascular events (total myocardial infarction, unstable angina, coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, total stroke). All included studies reported the effect of whole grain diets on risk factors for cardiovascular disease including blood lipids and blood pressure. All studies were in primary prevention populations and had an unclear or high risk of bias, and no studies had an intervention duration greater than 16 weeks. Overall, we found no difference between whole grain and control groups for total cholesterol (mean difference 0.07, 95% confidence interval -0.07 to 0.21; 6 studies (7 comparisons); 722 participants; low-quality evidence). Using GRADE, we assessed the overall quality of the available evidence on cholesterol as low. Four studies were funded by independent national and government funding bodies, while the remaining studies reported funding or partial funding by organisations with commercial interests in cereals. Authors' conclusions: There is insufficient evidence from RCTs of an effect of whole grain diets on cardiovascular outcomes or on major CVD risk factors such as blood lipids and blood pressure. Trials were at unclear or high risk of bias with small sample sizes and relatively short-term interventions, and the overall quality of the evidence was low. There is a need for well-designed, adequately powered RCTs with longer durations assessing cardiovascular events as well as cardiovascular risk factors

Diet, physical activity and behavioural interventions for the treatment of overweight or obese adolescents aged 12 to 17 years

Adolescent overweight and obesity has increased globally, and can be associated with short- and long-term health consequences. Modifying known dietary and behavioural risk factors through behaviour changing interventions (BCI) may help to reduce childhood overweight and obesity. This is an update of a review published in 2009. To assess the effects of diet, physical activity and behavioural interventions for the treatment of overweight or obese adolescents aged 12 to 17 years. We performed a systematic literature search in: CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, LILACS, and the trial registers ClinicalTrials.gov and ICTRP Search Portal. We checked references of identified studies and systematic reviews. There were no language restrictions. The date of the last search was July 2016 for all databases. We selected randomised controlled trials (RCTs) of diet, physical activity and behavioural interventions for treating overweight or obesity in adolescents aged 12 to 17 years. Two review authors independently assessed risk of bias, evaluated the overall quality of the evidence using the GRADE instrument and extracted data following the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions. We contacted trial authors for additional information. We included 44 completed RCTs (4781 participants) and 50 ongoing studies. The number of participants in each trial varied (10 to 521) as did the length of follow-up (6 to 24 months). Participants ages ranged from 12 to 17.5 years in all trials that reported mean age at baseline. Most of the trials used a multidisciplinary intervention with a combination of diet, physical activity and behavioural components. The content and duration of the intervention, its delivery and the comparators varied across trials. The studies contributing most information to outcomes of weight and body mass index (BMI) were from studies at a low risk of bias, but studies with a high risk of bias provided data on adverse events and quality of life.The mean difference (MD) of the change in BMI at the longest follow-up period in favour of BCI was -1.18 kg/m(2) (95% confidence interval (CI) -1.67 to -0.69); 2774 participants; 28 trials; low quality evidence. BCI lowered the change in BMI z score by -0.13 units (95% CI -0.21 to -0.05); 2399 participants; 20 trials; low quality evidence. BCI lowered body weight by -3.67 kg (95% CI -5.21 to -2.13); 1993 participants; 20 trials; moderate quality evidence. The effect on weight measures persisted in trials with 18 to 24 months' follow-up for both BMI (MD -1.49 kg/m(2) (95% CI -2.56 to -0.41); 760 participants; 6 trials and BMI z score MD -0.34 (95% CI -0.66 to -0.02); 602 participants; 5 trials).There were subgroup differences showing larger effects for both BMI and BMI z score in studies comparing interventions with no intervention/wait list control or usual care, compared with those testing concomitant interventions delivered to both the intervention and control group. There were no subgroup differences between interventions with and without parental involvement or by intervention type or setting (health care, community, school) or mode of delivery (individual versus group).The rate of adverse events in intervention and control groups was unclear with only five trials reporting harms, and of these, details were provided in only one (low quality evidence). None of the included studies reported on all-cause mortality, morbidity or socioeconomic effects.BCIs at the longest follow-up moderately improved adolescent's health-related quality of life (standardised mean difference 0.44 ((95% CI 0.09 to 0.79); P = 0.01; 972 participants; 7 trials; 8 comparisons; low quality of evidence) but not self-esteem.Trials were inconsistent in how they measured dietary intake, dietary behaviours, physical activity and behaviour. We found low quality evidence that multidisciplinary interventions involving a combination of diet, physical activity and behavioural components reduce measures of BMI and moderate quality evidence that they reduce weight in overweight or obese adolescents, mainly when compared with no treatment or waiting list controls. Inconsistent results, risk of bias or indirectness of outcome measures used mean that the evidence should be interpreted with caution. We have identified a large number of ongoing trials (50) which we will include in future updates of this review

What is the best way to evaluate social prescribing? A qualitative feasibility assessment for a national impact evaluation study in England

Objectives Despite significant investment in social prescribing in England over the last decade, we still do not know if it works, or how models of social prescribing fit within wider health and care policy and practice. This study explores current service delivery structures and assesses the feasibility of a national evaluation of the link worker model. Methods Semi-structured interviews were conducted between May and September 2020, with 25 key informants from across social prescribing services in England. Participants included link workers, voluntary, community and social enterprise staff, and those involved in policy and decision-making for social prescribing services. Interview and workshop transcripts were analysed thematically, adopting a framework approach. Results We found differences in how services are provided, including by individual link workers, and between organisations and regions. Standards, referral pathways, reporting, and monitoring structures differ or are lacking in voluntary services as compared to clinical services. People can self-refer to a link worker or be referred by a third party, but the lack of standardised processes generated confusion in both public and professional perceptions of the link worker model. We identified challenges in determining the appropriate outcomes and outcome measures needed to assess the impact of the link worker model. Conclusions The current varied service delivery structures in England poses major challenges for a national impact evaluation. Any future rigorous evaluation needs to be underpinned with national standardised outcomes and process measures which promote uniform data collection

Whole grain cereals for the primary or secondary prevention of cardiovascular disease.

BACKGROUND: There is evidence from observational studies that whole grains can have a beneficial effect on risk for cardiovascular disease (CVD). Earlier versions of this review found mainly short-term intervention studies. There are now longer-term randomised controlled trials (RCTs) available. This is an update and expansion of the original review conducted in 2007. OBJECTIVES: The aim of this systematic review was to assess the effect of whole grain foods or diets on total mortality, cardiovascular events, and cardiovascular risk factors (blood lipids, blood pressure) in healthy people or people who have established cardiovascular disease or related risk factors, using all eligible RCTs. SEARCH METHODS: We searched CENTRAL (Issue 8, 2016) in the Cochrane Library, MEDLINE (1946 to 31 August 2016), Embase (1980 to week 35 2016), and CINAHL Plus (1937 to 31 August 2016) on 31 August 2016. We also searched ClinicalTrials.gov on 5 July 2017 and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) on 6 July 2017. We checked reference lists of relevant articles and applied no language restrictions. SELECTION CRITERIA: We selected RCTs assessing the effects of whole grain foods or diets containing whole grains compared to foods or diets with a similar composition, over a minimum of 12 weeks, on cardiovascular disease and related risk factors. Eligible for inclusion were healthy adults, those at increased risk of CVD, or those previously diagnosed with CVD. DATA COLLECTION AND ANALYSIS: Two review authors independently selected studies. Data were extracted and quality-checked by one review author and checked by a second review author. A second review author checked the analyses. We assessed treatment effect using mean difference in a fixed-effect model and heterogeneity using the I2 statistic and the Chi2 test of heterogeneity. We assessed the overall quality of evidence using GRADE with GRADEpro software. MAIN RESULTS: We included nine RCTs randomising a total of 1414 participants (age range 24 to 70; mean age 45 to 59, where reported) to whole grain versus lower whole grain or refined grain control groups. We found no studies that reported the effect of whole grain diets on total cardiovascular mortality or cardiovascular events (total myocardial infarction, unstable angina, coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, total stroke). All included studies reported the effect of whole grain diets on risk factors for cardiovascular disease including blood lipids and blood pressure. All studies were in primary prevention populations and had an unclear or high risk of bias, and no studies had an intervention duration greater than 16 weeks.Overall, we found no difference between whole grain and control groups for total cholesterol (mean difference 0.07, 95% confidence interval -0.07 to 0.21; 6 studies (7 comparisons); 722 participants; low-quality evidence).Using GRADE, we assessed the overall quality of the available evidence on cholesterol as low. Four studies were funded by independent national and government funding bodies, while the remaining studies reported funding or partial funding by organisations with commercial interests in cereals. AUTHORS' CONCLUSIONS: There is insufficient evidence from RCTs of an effect of whole grain diets on cardiovascular outcomes or on major CVD risk factors such as blood lipids and blood pressure. Trials were at unclear or high risk of bias with small sample sizes and relatively short-term interventions, and the overall quality of the evidence was low. There is a need for well-designed, adequately powered RCTs with longer durations assessing cardiovascular events as well as cardiovascular risk factors

Association between vitamin D supplementation or serum vitamin D level and susceptibility to SARS-CoV-2 infection or COVID-19 including clinical course, morbidity and mortality outcomes? A systematic review

Objective To systemically review and critically appraise published studies of the association between vitamin D supplementation or serum vitamin D level and susceptibility to SARS-CoV-2 infection or COVID-19, including clinical course, morbidity and mortality outcomes. Design Systematic review. Data sources MEDLINE (OVID), Embase (OVID), Cochrane Central Register of Controlled Trials, MedRxiv and BioRxiv preprint databases. COVID-19 databases of the WHO, Cochrane, CEBM Oxford and Bern University up to 10 June 2020. Study selection Studies that assessed vitamin D supplementation and/or low serum vitamin D in patients acutely ill with, or at risk of, severe betacoronavirus infection (SARS-CoV, MERS-CoV, SARS-CoV-2). Data extraction Two authors independently extracted data using a predefined data extraction form and assessed risk of bias using the Downs and Black Quality Assessment Checklist. Results Searches elicited 449 papers, 59 studies were eligible full-text assessment and 4 met the eligibility criteria of this review. The four studies were narratively synthesised and included (1) a cross-sectional study (n=107) suggesting an inverse association between serum vitamin D and SARS-CoV-2; (2) a retrospective cohort study (348 598 participants, 449 cases) in which univariable analysis showed that vitamin D protects against COVID-19; (3) an ecological country level study demonstrating a negative correlation between vitamin D and COVID-19 case numbers and mortality; and (4) a case–control survey (n=1486) showing cases with confirmed/probable COVID-19 reported lower vitamin D supplementation. All studies were at high/unclear risk of bias. Conclusion There is no robust evidence of a negative association between vitamin D and COVID-19. No relevant randomised controlled trials were identified and there is no robust peer-reviewed published evidence of association between vitamin D levels and severity of symptoms or mortality due to COVID-19. Guideline producers should acknowledge that benefits of vitamin D supplementation in COVID-19 are as yet unproven despite increasing interest

Taxation of the fat content of foods for reducing their consumption and preventing obesity or other adverse health outcomes

Background: Overweight and obesity are increasing worldwide and are considered to be a major public health issue of the 21st century. Introducing taxation of the fat content in foods is considered a potentially powerful policy tool to reduce consumption of foods high in fat or saturated fat, or both. Objectives: To assess the effects of taxation of the fat content in food on consumption of total fat and saturated fat, energy intake, overweight, obesity, and other adverse health outcomes in the general population. Search methods: We searched CENTRAL, Cochrane Database of Systematic Reviews, MEDLINE, Embase, and 15 other databases and trial registers on 12 September 2019. We handsearched the reference lists of all records of included studies, searched websites of international organizations and institutions (14 October 2019), and contacted review advisory group members to identify planned, ongoing, or unpublished studies (26 February 2020). Selection criteria: In line with Cochrane Effective Practice and Organisation of Care Group (EPOC) criteria, we included the following study types: randomized controlled trials (RCTs), cluster‐randomized controlled trials (cRCTs), non‐randomized controlled trials (nRCTs), controlled before‐after (CBA) studies, and interrupted time series studies. We included studies that evaluated the effects of taxes on the fat content in foods. Such a tax could be expressed as sales, excise, or special value added tax (VAT) on the final product or an intermediary product. Eligible interventions were taxation at any level, with no restriction on the duration or the implementation level (i.e. local, regional, national, or multinational). Eligible study populations were children (zero to 17 years) and adults (18 years or older) from any country and setting. We excluded studies that focused on specific subgroups only (e.g. people receiving pharmaceutical intervention; people undergoing a surgical intervention; ill people who are overweight or obese as a side effect, such as those with thyroiditis and depression; and people with chronic illness). Primary outcomes were total fat consumption, consumption of saturated fat, energy intake through fat, energy intake through saturated fat, total energy intake, and incidence/prevalence of overweight or obesity. We did not exclude studies based on country, setting, comparison, or population. Data collection and analysis: We used standard Cochrane methods for all phases of the review. Risk of bias of the included studies was assessed using the criteria of Cochrane’s ‘Risk of bias’ tool and the EPOC Group’s guidance. Results of the review are summarized narratively and the certainty of the evidence was assessed using the GRADE approach. These steps were done by two review authors, independently. Main results: We identified 23,281 records from searching electronic databases and 1173 records from other sources, leading to a total of 24,454 records. Two studies met the criteria for inclusion in the review. Both included studies investigated the effect the Danish tax on saturated fat contained in selected food items between 2011 and 2012. Both studies used an interrupted time series design. Neither included study had a parallel control group from another geographic area. The included studies investigated an unbalanced panel of approximately 2000 households in Denmark and the sales data from a specific Danish supermarket chain (1293 stores). Therefore, the included studies did not address individual participants, and no restriction regarding age, sex, and socioeconomic characteristics were defined. We judged the overall risk of bias of the two included studies as unclear. For the outcome total consumption of fat, a reduction of 41.8 grams per week per person in a household (P < 0.001) was estimated. For the consumption of saturated fat, one study reported a reduction of 4.2% from minced beef sales, a reduction of 5.8% from cream sales, and an increase of 0.5% to sour cream sales (no measures of statistical precision were reported for these estimates). These estimates are based on a restricted number of food types and derived from sales data; they do not measure individual intake. Moreover, these estimates do not account for other relevant sources of fat intake (e.g. packaged or processed food) or other food outlets (e.g. restaurants or cafeterias); hence, we judged the evidence on the effect of taxation on total fat consumption or saturated fat consumption to be very uncertain. We did not identify evidence on the effect of the intervention on energy intake or the incidence or prevalence of overweight or obesity. Authors' conclusions: Given the very low quality of the evidence currently available, we are unable to reliably establish whether a tax on total fat or saturated fat is effective or ineffective in reducing consumption of total fat or saturated fat. There is currently no evidence on the effect of a tax on total fat or saturated fat on total energy intake or energy intake through saturated fat or total fat, or preventing the incidence or reducing the prevalence of overweight or obesity