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Cited by 417Diet and metabolism studiesDietary Effects on HealthNutritional Studies and Diet

Effects of Low-Carbohydrate Diets Versus Low-Fat Diets on Metabolic Risk Factors: A Meta-Analysis of Randomized Controlled Clinical Trials

Open access
Hu, Tian, Mills, Katherine T., Yao, Lu, Demanelis, Kathryn, Eloustaz, Mohamed, Yancy, William S., Kelly, Tanika N., He, Jiang +1 more·2012·American Journal of Epidemiology
DOI 10.1093/aje/kws264PMC PMC3530364
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Abstract

The effects of low-carbohydrate diets (≤45% of energy from carbohydrates) versus low-fat diets (≤30% of energy from fat) on metabolic risk factors were compared in a meta-analysis of randomized controlled trials. Twenty-three trials from multiple countries with a total of 2,788 participants met the predetermined eligibility criteria (from January 1, 1966 to June 20, 2011) and were included in the analyses. Data abstraction was conducted in duplicate by independent investigators. Both low-carbohydrate and low-fat diets lowered weight and improved metabolic risk factors. Compared with participants on low-fat diets, persons on low-carbohydrate diets experienced a slightly but statistically significantly lower reduction in total cholesterol (2.7 mg/dL; 95% confidence interval: 0.8, 4.6), and low density lipoprotein cholesterol (3.7 mg/dL; 95% confidence interval: 1.0, 6.4), but a greater increase in high density lipoprotein cholesterol (3.3 mg/dL; 95% confidence interval: 1.9, 4.7) and a greater decrease in triglycerides (-14.0 mg/dL; 95% confidence interval: -19.4, -8.7). Reductions in body weight, waist circumference and other metabolic risk factors were not significantly different between the 2 diets. These findings suggest that low-carbohydrate diets are at least as effective as low-fat diets at reducing weight and improving metabolic risk factors. Low-carbohydrate diets could be recommended to obese persons with abnormal metabolic risk factors for the purpose of weight loss. Studies demonstrating long-term effects of low-carbohydrate diets on cardiovascular events were warranted.

Integrity signals

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Crossref · 10.1093/aje/kws264

Cites

50 of 50 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 1 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    In the meta-analysis of all trials, the net change in the total cholesterol to HDL cholesterol ratio for low-carbohydrate versus low-fat diets was -0.1 (95% CI: -0.3, 0.1).

    “| TC:HDL ratio | 5 | -0.1 | -0.3, 0.1 | 1 | -0.5 | -0.8, -0.1 | 5 | -0.1 | -0.3, 0.1 | 5 | -0.1 | -0.3, 0.1 |”
    Quote in the paperSubstantial claim
  • Findingown data

    Twenty-three randomized controlled trials met all eligibility criteria and were included in the meta-analysis.

    “Of those, 23 studies met all of the eligibility criteria and were included in the meta-analysis”
    Quote in the paperSubstantial claim
  • Findingown data

    Among trials with at least 20 participants per group, the net change in systolic blood pressure for low-carbohydrate versus low-fat diets was -1.4 mmHg (95% CI: -3.9, 1.2).

    “| SBP, mmHg | 18 | -1.0 | -3.5, 1.5 | 10 | -0.1 | -2.5, 2.3 | 17 | -1.4 | -3.9, 1.2 | 17 | -1.6 | -4.2, 1.0 |”
    Quote in the paperNot a substantial claim
  • Findingown data

    Among trials with at least 70% completion, the net change in weight for low-carbohydrate versus low-fat diets was -1.3 kg (95% CI: -2.8, 0.2).

    “| Weight, kg | 22 | -1.0 | -2.2, 0.2 | 12 | -1.3 | -2.8, 0.2 | 19 | -1.3 | -2.5, -0.1 | 18 | -1.4 | -2.6, -0.2 |”
    Quote in the paperNot a substantial claim
  • Findingown data

    Subgroup analyses by gender, diabetic status, level of carbohydrate restriction, and study duration did not identify statistically significant differences in the majority of metabolic risk factor reductions between low-carbohydrate and low-fat diets.

    “Subgroup analyses by gender, diabetic status, level of carbohydrate restriction, and study duration did not identify statistically significant differences in the majority of metabolic risk factor reductions between low-carbohydrate and low-fat diets”
    Quote in the paperSubstantial claim
  • May combine two claims. 20
  • Classified as probably not a substantial claim. 11
  • The quote only partly states this claim. 6

  • May combine two claims.

    Findingown data

    The pooled mean net changes in diastolic blood pressure and serum insulin between low-carbohydrate and low-fat diets were not statistically significant.

    “The pooled mean net changes in diastolic blood pressures and serum insulin were also not significant (data not shown).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    Four studies were conducted in patients with diabetes, one in patients with prediabetes, and one in patients with coronary heart disease.

    “However, 4 studies were conducted in patients with diabetes (23,26,28,29), 1 was conducted in patients with prediabetes (31), and 1 was conducted in patients with coronary heart disease (23).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    Among trials with at least 70% completion, the net change in triglycerides for low-carbohydrate versus low-fat diets was -11.2 mg/dL (95% CI: -16.9, -5.5).

    “| TG, mg/dL | 20 | -14.0 -19.4, -8.7 | 12 | -11.2 -16.9, -5.5 | 19 | -13.4 -18.7, -8.1 | 18 | -13.6 -19.2, -8.0 |”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    Among trials with at least 70% completion, the net change in diastolic blood pressure for low-carbohydrate versus low-fat diets was -1.1 mmHg (95% CI: -2.4, 0.2).

    “| DBP, mmHg | 18 | -0.7 | -1.6, 0.2 | 10 | -1.1 | -2.4, 0.2 | 17 | -0.8 | -1.7, 0.2 | 17 | -0.8 | -1.7, 0.2 |”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In subgroup analysis, among younger participants, low-carbohydrate diets resulted in significantly greater reductions in systolic blood pressure (-2.7 mm Hg, 95% CI: -4.5 to -0.9), diastolic blood pressure (-1.5 mm Hg, 95% CI: -2.7 to -0.2), and serum insulin (-0.9 μIU/mL, 95% CI: -1.8 to -0.1) compared with older age groups, but these findings were not statistically significant after adjustment.

    “In addition, in the younger age group, low-carbohydrate diets resulted in significantly greater reductions in systolic blood pressure (-2.7 mm Hg, 95% CI: -4.5 to -0.9), diastolic blood pressure (-1.5 mm Hg, -2.7 to -0.2), and serum insulin (-0.9 μIU/mL, -1.8 to -0.1) as compared with results in the older age groups.However, these findings were not statistically significant after adjustment for”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In this meta-analysis, both low-carbohydrate and low-fat diets reduced body weight and improved metabolic risk factors.

    “Both low-carbohydrate and low-fat diets lowered weight and improved metabolic risk factors.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The pooled mean net change in systolic blood pressure between low-carbohydrate and low-fat diets was -1.0 mm Hg (95% CI: -3.5, 1.5) and was not statistically significant.

    “Pooled mean net changes in systolic blood pressure (-1.0 mm Hg, 95% CI: -3.5, 1.5), ratio of total to HDL cholesterol (-0.1, 95% CI: -0.3, 0.1), and fasting blood glucose (-0.3 mg/dL, 95% CI: -1.9, 1.3) were not significantly different between the 2 diets.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    Among trials with at least 70% completion, the net change in glucose for low-carbohydrate versus low-fat diets was -0.6 mg/dL (95% CI: -2.7, 1.4).

    “| Glucose, mg/dL | 14 | -0.3 | -1.9, 1.3 | 10 | -0.6 | -2.7, 1.4 | 13 | -0.4 | -2.1, 1.4 | 13 | -0.4 | -2.1, 1.4 |”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingcitation

    All included trials were parallel except for one trial that had a factorial design.

    “All trials were parallel except for 1 trial that had a factorial design (13).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The pooled mean net change in fasting blood glucose between low-carbohydrate and low-fat diets was -0.3 mg/dL (95% CI: -1.9, 1.3) and was not statistically significant.

    “Pooled mean net changes in systolic blood pressure (-1.0 mm Hg, 95% CI: -3.5, 1.5), ratio of total to HDL cholesterol (-0.1, 95% CI: -0.3, 0.1), and fasting blood glucose (-0.3 mg/dL, 95% CI: -1.9, 1.3) were not significantly different between the 2 diets.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    The differences between low-carbohydrate and low-fat diets in total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides remained statistically significant after correction for multiple comparisons.

    “These differences remained statistically significant after correction for multiple comparisons.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The included trials had a total of 2,788 participants, with 1,392 on low-carbohydrate diets and 1,396 on low-fat diets.

    “These studies included data from 2,788 trial participants (1,392 on low-carbohydrate diets and 1,396 on low-fat diets).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    Among trials with at least 70% completion, the net change in systolic blood pressure for low-carbohydrate versus low-fat diets was -0.1 mmHg (95% CI: -2.5, 2.3).

    “| SBP, mmHg | 18 | -1.0 | -3.5, 1.5 | 10 | -0.1 | -2.5, 2.3 | 17 | -1.4 | -3.9, 1.2 | 17 | -1.6 | -4.2, 1.0 |”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The pooled mean net change in body weight between low-carbohydrate and low-fat diets was -1.0 kg (95% CI: -2.2, 0.2) and was not statistically significant.

    “Pooled mean net changes and 95% confidence intervals representing differences between the diets in body weight (-1.0 kg, 95% confidence interval (CI): -2.2, 0.2) and waist circumference (-0.1 cm, 95% CI: -0.6, 0.4) reductions were not statistically significant.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The goal dietary nutritional composition varied across studies, with carbohydrate consumption ranging from 4% to 45% (weighted mean, 23%) of energy intake in the low-carbohydrate group and fat ranging from 10% to 30% (weighted mean, 26%) of energy intake in the low-fat group.

    “The goal dietary nutritional composition varied across the studies, with carbohydrate consumption ranging from 4% to 45% (weighted mean, 23%) of energy intake in the low-carbohydrate group and fat ranging from 10% to 30% (weighted mean, 26%) of energy intake in the low-fat group.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The pooled mean net change in the ratio of total to HDL cholesterol between low-carbohydrate and low-fat diets was -0.1 (95% CI: -0.3, 0.1) and was not statistically significant.

    “Pooled mean net changes in systolic blood pressure (-1.0 mm Hg, 95% CI: -3.5, 1.5), ratio of total to HDL cholesterol (-0.1, 95% CI: -0.3, 0.1), and fasting blood glucose (-0.3 mg/dL, 95% CI: -1.9, 1.3) were not significantly different between the 2 diets.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    There was no significant heterogeneity among trials in net changes in total cholesterol, triglycerides, waist circumference, fasting blood glucose, or serum insulin.

    “There was no significant heterogeneity in the net changes in total cholesterol (I 2 = 0.2%, P = 0.45), triglycerides (I 2 = 55.6%,P = 0.07), waist circumference (I 2 = 12.5%, P = 0.33), fasting blood glucose (I 2 = 41.2%,P = 0.06), or serum insulin (I 2 = 7.8%, P = 0.29) among these trials.”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    Among trials with at least 70% completion, the net change in insulin for low-carbohydrate versus low-fat diets was -0.1 IU/mL (95% CI: -1.0, 0.8).

    “| Insulin, IU/mL | 12 | -0.1 | -0.8, 0.6 | 8 | -0.1 | -1.0, 0.8 | 10 | -0.1 | -0.9, 0.7 | 10 | -0.3 | -0.9, 0.7 |”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Self-reported mean energy intake weighted by trial sample sizes was similar for both diets at approximately 2,000 kcal.

    “Self-reported mean energy intake weighted by trial sample sizes was similar for both diets at approximately 2,000 kcal.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The pooled mean net change in waist circumference between low-carbohydrate and low-fat diets was -0.1 cm (95% CI: -0.6, 0.4) and was not statistically significant.

    “Pooled mean net changes and 95% confidence intervals representing differences between the diets in body weight (-1.0 kg, 95% confidence interval (CI): -2.2, 0.2) and waist circumference (-0.1 cm, 95% CI: -0.6, 0.4) reductions were not statistically significant.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    Study duration ranged from 6 to 24 months, and 16 studies had an intervention duration of 12 months or longer.

    “Study duration ranged from 6 to 24 months, and 16 studies had an intervention duration of 12 months or longer”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Disagreement was resolved by consensus with additional investigators.

    “Disagreement was resolved by consensus with additional investigators.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductnone given

    Two investigators independently reviewed all potentially relevant publications and made decisions on inclusion.

    “Two investigators independently reviewed all potentially relevant publications and made decisions on inclusion.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The ratio of total to HDL cholesterol has been identified as a predictor of coronary heart disease.

    “the reduction in ratio of total to HDL cholesterol, which has been identified as a predictor of coronary heart disease (35), was not significantly different between the 2 diets.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [35] Gardner, 1996, Association of small low-density lipoprotein particles with the incidence of coronary artery disease in men and women, JAMA source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Two investigators independently abstracted the data in duplicate using a standardized data collection form.

    “Two investigators independently abstracted the data in duplicate using a standardized data collection form.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductnone given

    The meta-analysis had a sample size of 2,788, which provided power to detect statistically significant mean differences, assess publication bias, and conduct sensitivity and subgroup analyses.

    “This meta-analysis had a sample size of 2,788, which provided the power to detect statistically significant mean differences, assess publication bias, and conduct sensitivity and subgroup analyses.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Both low-carbohydrate and low-fat diets were equally effective at reducing body weight and waist circumference.

    “In the present meta-analysis of randomized controlled trials comparing low-carbohydrate diets with low-fat diets, we found that both diets were equally effective at reducing body weight and waist circumference.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    Baseline levels of body weight and metabolic risk factors were similar between the two diets in each study but varied among studies.

    “Baseline levels of body weight and metabolic risk factors were similar between the 2 diets in each study but varied among studies.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    Losses to follow-up were substantial, especially in some trials, and almost half of the included studies had completion rates less than 70%.

    “First, losses to follow-up were substantial, especially in some trials (8,22,29).Almost half of the studies included in our meta-analysis had completion rates less than 70%.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Trial participants were usually not blinded to their assignment because of the nature of the dietary intervention.

    “Trial participants were usually not blinded to their assignment because of the nature of the intervention-most interventions provided dietary instruction, leaving food buying and/ or preparation to the participants.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Low-carbohydrate diets are at least as effective as low-fat diets at reducing weight and improving metabolic risk factors.

    “These findings suggest that low-carbohydrate diets are at least as effective as low-fat diets at reducing weight and improving metabolic risk factors.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Data abstraction was conducted in duplicate by independent investigators.

    “Data abstraction was conducted in duplicate by independent investigators.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Study design and conductnone given

    The meta-analysis was conducted following a stringent protocol.

    “We conducted this meta-analysis following a stringent protocol.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Low-carbohydrate diets are at least as effective as low-fat diets for weight loss, regardless of gender, age, length of intervention, diabetes status, and level of carbohydrate restriction.

    “Our findings suggest that low-carbohydrate diets are at least as effective as low-fat diets for weight loss, regardless of gender, age, length of intervention, diabetes status, and level of carbohydrate restriction.”
    Quote in the paperSubstantial claim
34 of 34

  • The paper relies on this without support.

    Many clinical trials of low-carbohydrate diets have small sample sizes and insufficient statistical power to detect small changes in metabolic risk factors that may have public health importance.

    “Many clinical trials of lowcarbohydrate diets have small sample sizes and insufficient statistical power to detect small changes in metabolic risk factors that may have public health importance.”

  • The paper relies on this without support.

    Low-carbohydrate diets may include significant amounts of fat and cholesterol, which have been associated with elevated LDL cholesterol levels, raising concern about adverse effects on metabolic risk factors.

    “Because lowcarbohydrate diets may include significant amounts of fat and cholesterol, which have been associated with elevated low density lipoprotein (LDL) cholesterol levels, there is concern about their adverse effects on metabolic risk factors.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Insulin estimate is not centered in its confidence interval

    Minor

    For the healthy-participant sensitivity analysis, the reported insulin net change is −0.3, whereas the midpoint of its stated 95% confidence interval is −0.1. That difference exceeds rounding to one decimal place for the symmetric confidence intervals described in the methods.

    Reported -0.3 · recomputed -0.1

  • Duration subgroup changes from at least to more than one year

    Minor

    The methods define the longer-duration subgroup as interventions lasting at least 12 months, which includes exactly one year. The results describe that subgroup as lasting more than one year, which excludes those trials.

2 of 2

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Authors
Hu, T., Mills, K. T., Yao, L., Demanelis, K., Eloustaz, M., Yancy, W. S., Kelly, T. N., He, J., & Bazzano, L. A.
Affiliations
Tulane University (US)
Corresponding author
Bazzano, Lydia A.
ORCID
Venue
American Journal of Epidemiology
Publisher
Oxford University Press (OUP)
Published
2012-10-01
Volume
176
Issue
suppl_7
Pages
S44-S54
ISSN
  • 0002-9262 (ISSN-L)
  • 1476-6256
DOI
10.1093/aje/kws264
PMC
PMC3530364
OpenAlex
W2135997989
Semantic Scholar
471641c6f74cd8ae96d1ba087339e5d2efad13ce
Cited by
417
References
51
Citations by year
2026: 9 · 2025: 20 · 2024: 16 · 2023: 24 · 2022: 34 · 2021: 32 · 2020: 37 · 2019: 37 · 2018: 37 · 2017: 28 · 2016: 41 · 2015: 55 · 2014: 27 · 2013: 20
FWCI
3.51
Type
journal article
Language
en
Open access
Locations
  • American Journal of Epidemiology (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • Tulane University
  • National Institutes of Health
  • School of Medicine, Duke University
  • National Heart, Lung, and Blood Institute (K08HL091108)
Topics
  • Health Sciences › Medicine › Physiology › Diet and metabolism studies
  • Health Sciences › Medicine › Physiology › Dietary Effects on Health
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Nutritional Studies and Diet
Keywords
low-carbohydrate diet, low-fat diet, metabolic risk factors, weight loss, obesity, cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, waist circumference, dietary fat restriction
MeSH terms
Adult, Age Factors, Blood Glucose, Blood Pressure, Body Weight, Cholesterol, Female, Humans, Insulin, Cholesterol, HDL, Cholesterol, LDL, Male, Middle Aged, Risk Factors, Sex Factors, Triglycerides, Randomized Controlled Trials as Topic, Diet, Fat-Restricted, Metabolic Syndrome, Diet, Carbohydrate-Restricted, Waist Circumference, Young Adult

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