Effect of a very low-carbohydrate ketogenic diet vs recommended diets in patients with type 2 diabetes: a meta-analysis
Abstract
Context: There is renewed interest in using very low-carbohydrate ketogenic (VLCK) diets to manage diabetes. Many clinical trials have been published, often with mixed results. Objective: This meta-analysis compares the effect of a VLCK diet on glycemic control, body weight, lipid profile, medication use, and dropouts with that of recommended diets for 12 weeks or longer in people with type 2 diabetes. Data Sources: Ovid MEDLINE, Ovid Embase, CENTRAL, and CINAHL databases were searched (January 1980 through September 2019). Study Selection: Two authors independently reviewed search results to select randomized controlled trials (RCTs) comparing a VLCK diet (carbohydrate intake < 50 g/d or < 10% of total energy) with any recommended diet for type 2 diabetes in adults. Discrepancies were resolved after consulting with the third author. Data Extraction: Eight RCTs with 648 participants were identified. Results: Compared with control diets, the VLCK diet resulted in a greater decrease in hemoglobin A1c after 3 months (weighted mean difference[WMD]: −6.7 mmol/mol; 95%CI, −9.0 to −4.4) (WMD: −0.61%; 95%CI, −0.82 to −0.40; P < 0.001; moderate-certainty evidence) and after 6 months (WMD: −6.3 mmol/mol; 95%CI, −9.3 to −3.5) (WMD: −0.58%; 95%CI, −0.85 to −0.32; low-certainty evidence). There was a significantly greater weight loss with the VLCK diet after 3 months (WMD: −2.91 kg; 95%CI, −4.88 to −0.95; low-certainty evidence) and after 6 months (WMD: −2.84 kg; 95%CI, −5.29 to −0.39; low-certainty evidence). The VLCK diet was not better than a control diet after 12 months. It was superior in decreasing triglyceride levels, increasing high-density lipoprotein cholesterol levels, and reducing the use of antidiabetic medications for up to 12 months. Conclusion: The VLCK diet appears to control glycemia and decrease body weight for up to 6 months in people with obesity and diabetes. Beneficial changes in serum triglycerides and high-density lipoprotein cholesterol, along with reductions in antidiabetic medications, continued in the VLCK group until 12 months. However, the quality of currently available evidence is not sufficient to recommend VLCK diets. A major limitation of the VLCK diet is patients’ lack of adherence to carbohydrate restriction. Systematic Review Registration: PROSPERO registration number CRD42020154700
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The LDL-C increase (8.49 mg/dL) is somewhat higher than other studies, likely due to the strict KD criteria (> 45% fat, < 10% carbohydrate).
“while the LDL-C increase (8.49 mg/dL) is somewhat higher than other studies [21], likely due to our strict KD criteria (> 45% fat, < 10% carbohydrate) [32].”
From Ketogenic diet-induced changes in adult lipid metabolism: a comprehensive systematic review and meta-regression of randomized controlled trials (2026) · cites this paper as [32]
Seventeen meta-analyses were included.
“Seventeen meta-analyses were included (Fig. 1 and Additional file 2: Table S3) [1, 2, 15–17, 34–45].”
From Effects of ketogenic diet on health outcomes: an umbrella review of meta-analyses of randomized clinical trials (2023) · cites this paper as [35]
KD for 12 months was associated with increased LDL-C in adults with T2DM compared with regular diet (MD 6.35 mg/dL, 95% CI 2.02 to 10.69, MCID 3.87 mg/dL).
“KD for 12 months was associated with increased LDL-C in adults with T2DM compared with regular diet (MD, 6.35 mg/dL; 95% CI, 2.02 to 10.69, MCID threshold 3.87 mg/dL) [14, 35].”
From Effects of ketogenic diet on health outcomes: an umbrella review of meta-analyses of randomized clinical trials (2023) · cites this paper as [35]
Lowered dietary carbohydrate intake effectively reduced serum triglyceride levels at 3 months, with further reduction by month 12.
“With regards to KD effects on lipid profiles, our results demonstrate an effective reduction in serum triglyceride levels with 3 months of lowered dietary carbohydrate intake, with even further reduction by month 12 [35].”
From Effects of ketogenic diet on health outcomes: an umbrella review of meta-analyses of randomized clinical trials (2023) · cites this paper as [35]
Ketogenic diet could induce rapid weight loss in the initial 6 months, after which further weight loss was hardly achieved.
“Our findings demonstrated that KD could induce a rapid weight loss in the initial phase of 6 months, after which time further weight loss was hardly achieved [35].”
From Effects of ketogenic diet on health outcomes: an umbrella review of meta-analyses of randomized clinical trials (2023) · cites this paper as [35]
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“The observed TG decrease (−19.96 mg/dL) aligns with Rafiullah et al., who reported −22.1 mg/dL in T2DM, while the LDL-C increase (8.49 mg/dL) is somewhat higher than other studies [21], likely due to our strict KD criteria (> 45% fat, 10% carbohydrate) [32].”
Influential
- Authors
- Rafiullah, M., Musambil, M., & David, S. K.
- Affiliations
- King Saud University (SA)
- Corresponding author
- Rafiullah, Mohamed
- Venue
- Nutrition Reviews
- Publisher
- Oxford University Press (OUP)
- Published
- 2021-08-02
- Volume
- 80
- Issue
- 3
- Pages
- 488-502
- ISSN
- 0029-6643 (ISSN-L)
- 1753-4887
- OpenAlex
- W3188984182
- Cited by
- 86
- References
- 33
- Citations by year
- 2026: 13 · 2025: 14 · 2024: 29 · 2023: 20 · 2022: 10
- FWCI
- 1.97
- Type
- journal article
- Language
- en
- Open access
- closed
- Licence
- academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model (vor)
- Locations
- Nutrition Reviews (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Physiology › Diet and metabolism studies
- Health Sciences › Medicine › Physiology › Dietary Effects on Health
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes Management and Research
- Keywords
- type 2 diabetes, glycemic control, HbA1c, weight loss, lipid profile, triglycerides, HDL cholesterol, antidiabetic medication use, dietary intervention, diabetes management, dropout rates, body weight, insulin secretion, insulin sensitivity index, insulin resistance index, insulin secretion index
- MeSH terms
- Adult, Diabetes Mellitus, Type 2, Glycated Hemoglobin, Humans, Weight Loss, Diet, Carbohydrate-Restricted, Diet, Ketogenic
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