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

Abstract

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, I(2)=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/m(2), 95% confidence interval -0.76 to -0.26, nine trials, I(2)=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.

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  • Authors+Show Affiliations

    ,

    Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK. L.hooper@uea.ac.uk

    , , , ,

    Source

    BMJ (Clinical research ed.) 345: 2012 Dec 06 pg e7666

    MeSH

    Adult
    Alcohol Drinking
    Blood Pressure
    Body Mass Index
    Child
    Cohort Studies
    Diet, Fat-Restricted
    Dietary Carbohydrates
    Dietary Fats
    Energy Intake
    Female
    Humans
    Lipids
    Male
    Randomized Controlled Trials as Topic
    Risk Factors
    Waist Circumference
    Weight Loss

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Research Support, Non-U.S. Gov't
    Review
    Systematic Review

    Language

    eng

    PubMed ID

    23220130

    Citation

    Hooper, Lee, et al. "Effect of Reducing Total Fat Intake On Body Weight: Systematic Review and Meta-analysis of Randomised Controlled Trials and Cohort Studies." BMJ (Clinical Research Ed.), vol. 345, 2012, pp. e7666.
    Hooper L, Abdelhamid A, Moore HJ, et al. Effect of reducing total fat intake on body weight: systematic review and meta-analysis of randomised controlled trials and cohort studies. BMJ. 2012;345:e7666.
    Hooper, L., Abdelhamid, A., Moore, H. J., Douthwaite, W., Skeaff, C. M., & Summerbell, C. D. (2012). Effect of reducing total fat intake on body weight: systematic review and meta-analysis of randomised controlled trials and cohort studies. BMJ (Clinical Research Ed.), 345, pp. e7666. doi:10.1136/bmj.e7666.
    Hooper L, et al. Effect of Reducing Total Fat Intake On Body Weight: Systematic Review and Meta-analysis of Randomised Controlled Trials and Cohort Studies. BMJ. 2012 Dec 6;345:e7666. PubMed PMID: 23220130.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Effect of reducing total fat intake on body weight: systematic review and meta-analysis of randomised controlled trials and cohort studies. AU - Hooper,Lee, AU - Abdelhamid,Asmaa, AU - Moore,Helen J, AU - Douthwaite,Wayne, AU - Skeaff,C Murray, AU - Summerbell,Carolyn D, Y1 - 2012/12/06/ PY - 2012/12/11/entrez PY - 2012/12/12/pubmed PY - 2013/2/5/medline SP - e7666 EP - e7666 JF - BMJ (Clinical research ed.) JO - BMJ VL - 345 N2 - 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, I(2)=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/m(2), 95% confidence interval -0.76 to -0.26, nine trials, I(2)=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. SN - 1756-1833 UR - https://www.unboundmedicine.com/medline/citation/23220130/full_citation L2 - http://www.bmj.com/cgi/pmidlookup?view=long&pmid=23220130 DB - PRIME DP - Unbound Medicine ER -