The Effect of Low-Fat and Low-Carbohydrate Diets on Weight Loss and Lipid Levels: A Systematic Review and Meta-Analysis

Nutrients. 2020 Dec 9;12(12):3774. doi: 10.3390/nu12123774.


Background: The rise in obesity has emphasised a focus on lifestyle and dietary habits. We aimed to address the debate between low-carbohydrate and low-fat diets and compare their effects on body weight, low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), total cholesterol, and triglycerides in an adult population.

Method: Medline and Web of Science were searched for randomised controlled trials (RCTs) comparing low-fat and low-carbohydrate diets up to September 2019. Three independent reviewers extracted data. Risk of bias was assessed using the Cochrane tool. The meta-analysis was stratified by follow-up time using the random-effects models.

Results: This meta-analysis of 38 studies assessed a total of 6499 adults. At 6-12 months, pooled analyses of mean differences of low-carbohydrate vs. low-fat diets favoured the low-carbohydrate diet for average weight change (mean difference -1.30 kg; 95% CI -2.02 to -0.57), HDL (0.05 mmol/L; 95% CI 0.03 to 0.08), and triglycerides (TG) (-0.10 mmol/L; -0.16 to -0.04), and favoured the low-fat diet for LDL (0.07 mmol/L; 95% CI 0.02 to 0.12) and total cholesterol (0.10 mmol/L; 95% CI 0.02 to 0.18). Conclusion and Relevance: This meta-analysis suggests that low-carbohydrate diets are effective at improving weight loss, HDL and TG lipid profiles. However, this must be balanced with potential consequences of raised LDL and total cholesterol in the long-term.

Keywords: cardiology; cardiovascular outcomes; cholesterol; lipid panel; low carbohydrate diet; low fat diet; nutrition; preventative medicine; weight loss.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • Adult
  • Cholesterol, HDL / blood
  • Cholesterol, LDL / blood
  • Diet, Carbohydrate-Restricted / methods*
  • Diet, Fat-Restricted / methods*
  • Humans
  • Lipids / blood*
  • Triglycerides / blood
  • Weight Loss*


  • Cholesterol, HDL
  • Cholesterol, LDL
  • Lipids
  • Triglycerides