Carolyn Summerbell

Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review.

Abstract Objective To review systematically the evidence for an effect of long chain and shorter chain omega 3 fatty acids on total mortality, cardiovascular events, and cancer. Data sources Electronic databases searched to February 2002; authors contacted and bibliographies of randomised controlled trials (RCTs) checked to locate studies. Review methods Review of RCTs of omega 3 intake for 3 6 months in adults (with or without risk factors for cardiovascular disease) with data on a relevant outcome. Cohort studies that estimated omega 3 intake and related this to clinical outcome during at least 6 months were also included. Application of inclusion criteria, data extraction, and quality assessments were performed independently in duplicate. Results Of 15 159 titles and abstracts assessed, 48 RCTs (36 913 participants) and 41 cohort studies were analysed. The trial results were inconsistent. The pooled estimate showed no strong evidence of reduced risk of total mortality (relative risk 0.87, 95% confidence interval 0.73 to 1.03) or combined cardiovascular events (0.95, 0.82 to 1.12) in participants taking additional omega 3 fats. The few studies at low risk of bias were more consistent, but they showed no effect of omega 3 on total mortality (0.98, 0.70 to 1.36) or cardiovascular events (1.09, 0.87 to 1.37). When data from the subgroup of studies of long chain omega 3 fats were analysed separately, total mortality (0.86, 0.70 to 1.04; 138 events) and cardiovascular events (0.93, 0.79 to 1.11) were not clearly reduced. Neither RCTs nor cohort studies suggested increased risk of cancer with a higher intake of omega 3 (trials: 1.07, 0.88 to 1.30; cohort studies: 1.02, 0.87 to 1.19), but clinically important harm could not be excluded. Conclusion Long chain and shorter chain omega 3 fats do not have a clear effect on total mortality, combined cardiovascular events, or cancer.

Systematic review of school-based interventions that focus on changing dietary intake and physical activity levels to prevent childhood obesity: an update to the obesity guidance produced by the National Institute for Health and Clinical Excellence

To determine the effectiveness of school‐based interventions that focus on changing dietary intake and physical activity levels to prevent childhood obesity. MEDLINE and EMBASE were searched (January 2006 to September 2007) for controlled trials of school‐based lifestyle interventions, minimum duration of 12 weeks, reporting weight outcome. Thirty‐eight studies were included; 15 new studies and 23 studies included within the National Institute for Health and Clinical Excellence obesity guidance. One of three diet studies, five of 15 physical activity studies and nine of 20 combined diet and physical activity studies demonstrated significant and positive differences between intervention and control for body mass index. There is insufficient evidence to assess the effectiveness of dietary interventions or diet vs. physical activity interventions. School‐based physical activity interventions may help children maintain a healthy weight but the results are inconsistent and short‐term. Physical activity interventions may be more successful in younger children and in girls. Studies were heterogeneous, making it difficult to generalize about what interventions are effective. The findings are inconsistent, but overall suggest that combined diet and physical activity school‐based interventions may help prevent children becoming overweight in the long term. Physical activity interventions, particularly in girls in primary schools, may help to prevent these children from becoming overweight in the short term.

Evidence that the prevalence of childhood overweight is plateauing: data from nine countries

Until quite recently, there has been a widespread belief in the popular media and scientific literature that the prevalence of childhood obesity is rapidly increasing. However, high quality evidence has emerged from several countries suggesting that the rise in the prevalence has slowed appreciably, or even plateaued. This review brings together such data from nine countries (Australia, China, England, France, Netherlands, New Zealand, Sweden, Switzerland and USA), with data from 467,294 children aged 2-19 years. The mean unweighted rate of change in prevalence of overweight and obesity was +0.00 (0.49)% per year across all age ×sex groups and all countries between 1995 and 2008. For overweight alone, the figure was +0.01 (0.56)%, and for obesity alone -0.01 (0.24)%. Rates of change differed by sex, age, socioeconomic status and ethnicity. While the prevalence of overweight and obesity appears to be stabilizing at different levels in different countries, it remains high, and a significant public health issue. Possible reasons for the apparent flattening are hypothesised.

The impact of maternal BMI status on pregnancy outcomes with immediate short-term obstetric resource implications: a meta-analysis.

Obesity is rising in the obstetric population, yet there is an absence of services and guidance for the management of maternal obesity. This systematic review aimed to investigate relationships between obesity and impact on obstetric care. Literature was systematically searched for cohort studies of pregnant women with anthropometric measurements recorded within 16‐weeks gestation, followed up for the term of the pregnancy, with at least one obese and one comparison group. Two researchers independently data‐extracted and quality‐assessed each included study. Outcome measures were those that directly or indirectly impacted on maternity resources. Primary outcomes included instrumental delivery, caesarean delivery, duration of hospital stay, neonatal intensive care, neonatal trauma, haemorrhage, infection and 3rd/4th degree tears. Meta‐analysis shows a significant relationship between obesity and increased odds of caesarean and instrumental deliveries, haemorrhage, infection, longer duration of hospital stay and increased neonatal intensive care requirement. Maternal obesity significantly contributes to a poorer prognosis for mother and baby during delivery and in the immediate post‐partum period. National clinical guidelines for management of obese pregnant women, and public health interventions to help safeguard the health of mothers and their babies are urgently required.

A nationally representative study of maternal obesity in England, UK: trends in incidence and demographic inequalities in 619 323 births, 1989–2007

Background:There is an absence of national statistics for maternal obesity in the UK. This study is the first to describe a nationally representative maternal obesity research data set in England.Design:Retrospective epidemiological study of first trimester obesity.Methods:Data from 34 maternity units were analysed, including 619 323 births between 1989 and 2007. Data analysis included trends in first trimester maternal body bass index status over time, and geographical distribution of maternal obesity. Population demographics including maternal age, parity, ethnic group, deprivation and employment were analysed to identify any maternal obesity-associated health inequalities. All demographics were tested for multicollinearity. Logistic regression analyses were adjusted for all demographics as confounders.Results:First trimester maternal obesity is significantly increasing over time, having more than doubled from 7.6% to 15.6% over 19 years (P<0.001), and shows geographic variation in incidence. There are also demographic health inequalities associated with maternal obesity, including increased odds of being obese with increasing age, parity, Black ethnic group and deprivation. There is also an association between morbid obesity and increased levels of unemployment.Conclusions:The increase in maternal obesity has serious implications for the health of mothers, infants and service providers, yielding an additional 47 500 women per year requiring high dependency care in England. The demography of women most at risk of first trimester obesity highlights health inequalities associated with maternal obesity, which urgently needs to be addressed.

Trends in maternal obesity incidence rates, demographic predictors, and health inequalities in 36 821 women over a 15‐year period

Objective  The aim of this study was to identify trends in maternal obesity incidence over time and to identify those women most at risk and potential‐associated health inequalities.

Television Food Advertising to Children: A Global Perspective

OBJECTIVES We compared television food advertising to children in several countries. METHODS We undertook a collaboration among 13 research groups in Australia, Asia, Western Europe, and North and South America. Each group recorded programming for 2 weekdays and 2 weekend days between 6:00 and 22:00, for the 3 channels most watched by children, between October 2007 and March 2008. We classified food advertisements as core (nutrient dense, low in energy), noncore (high in undesirable nutrients or energy, as defined by dietary standards), or miscellaneous. We also categorized thematic content (promotional characters and premiums). RESULTS Food advertisements composed 11% to 29% of advertisements. Noncore foods were featured in 53% to 87% of food advertisements, and the rate of noncore food advertising was higher during childrens peak viewing times. Most food advertisements containing persuasive marketing were for noncore products. CONCLUSIONS Across all sampled countries, children were exposed to high volumes of television advertising for unhealthy foods, featuring child-oriented persuasive techniques. Because of the proven connections between food advertising, preferences, and consumption, our findings lend support to calls for regulation of food advertising during childrens peak viewing times.

Interventions for preventing obesity in childhood. A systematic review

Background The prevalence of obesity and overweight is increasing worldwide. Obesity in children impacts on their health in both short‐ and long‐term. Obesity prevention strategies are poorly understood.

Effect of reducing total fat intake on body weight: systematic review and meta-analysis of randomised controlled trials and cohort studies

Objective To investigate the relation between total fat intake and body weight in adults and children. Design Systematic review and meta-analysis of randomised controlled trials and cohort studies. Data sources Medline, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials to June 2010. Inclusion criteria Randomised controlled trials and cohort studies of adults or children that compared lower versus usual total fat intake and assessed the effects on measures of body fatness (body weight, body mass index, or waist circumference) after at least six months (randomised controlled trials) or one year (in cohorts). Randomised controlled trials with any intention to reduce weight in participants or confounded by additional medical or lifestyle interventions were excluded. Data extraction Data were extracted and validity was assessed independently and in duplicate. Random effects meta-analyses, subgroups, sensitivity analyses, and metaregression were done. Results 33 randomised controlled trials (73 589 participants) and 10 cohort studies were included, all from developed countries. Meta-analysis of data from the trials suggested that diets lower in total fat were associated with lower relative body weight (by 1.6 kg, 95% confidence interval −2.0 to −1.2 kg, I2=75%, 57 735 participants). Lower weight gain in the low fat arm compared with the control arm was consistent across trials, but the size of the effect varied. Metaregression suggested that greater reduction in total fat intake and lower baseline fat intake were associated with greater relative weight loss, explaining most of the heterogeneity. The significant effect of a low fat diet on weight was not lost in sensitivity analyses (including removing trials that expended greater time and attention on low fat groups). Lower total fat intake also led to lower body mass index (−0.51 kg/m2, 95% confidence interval −0.76 to −0.26, nine trials, I2=77%) and waist circumference (by 0.3 cm, 95% confidence interval −0.58 to −0.02, 15 671 women, one trial). There was no suggestion of negative effects on other cardiovascular risk factors (lipid levels or blood pressure). GRADE assessment suggested high quality evidence for the relation between total fat intake and body weight in adults. Only one randomised controlled trial and three cohort studies were found in children and young people, but these confirmed a positive relation between total fat intake and weight gain. Conclusions There is high quality, consistent evidence that reduction of total fat intake has been achieved in large numbers of both healthy and at risk trial participants over many years. Lower total fat intake leads to small but statistically significant and clinically meaningful, sustained reductions in body weight in adults in studies with baseline fat intakes of 28-43% of energy intake and durations from six months to over eight years. Evidence supports a similar effect in children and young people.

Obesity: diagnosis, prevention, and treatment; evidence based answers to common questions

Paediatric obesity is now common in the UK, as in other developed countries. A literature search was conducted and evidence based answers to five frequently answered questions sought. Recommendations for diagnosis are given. Although there is no conclusive evidence that the condition is preventable, a number of treatment approaches are promising.