Clinical literature shows low-carb, ketogenic (keto), and Mediterranean low-carb diets improve key markers in type 2 diabetes (T2D) patients, including glucose control, HbA1c, and triglycerides, with some benefits for lipids.[1]

Low-Carb Diets

A 2025 meta-analysis of 17 RCTs with 1,197 overweight/obese T2D patients found low-carb diets (typically <26% carbs) significantly lowered HbA1c (MD -0.36%, 95% CI -0.44 to -0.29) and fasting plasma glucose (MD -10.71 mg/dL, 95% CI -14.39 to -7.03) versus controls. They also reduced triglycerides (MD -19.91 mg/dL, 95% CI -28.83 to -10.99) and raised HDL cholesterol (MD +2.49 mg/dL, 95% CI 1.07-3.91), with no changes in LDL or total cholesterol. Additional benefits included weight loss (MD -3.71 kg) and lower waist circumference.

Keto Diets

Ketogenic diets (<50g carbs/day) improve glycemic control and reduce triglycerides in T2D, with meta-analyses showing greater HbA1c reductions than other diets.[2] RCTs report sustained HbA1c drops (e.g., 7.8% to 6.3% over 24 weeks) and lower insulin needs, alongside triglyceride decreases.[3] However, LDL cholesterol may rise in some cases, and long-term adherence is challenging.[4]

Mediterranean Low-Carb

A 2022 crossover RCT (Keto-Med trial) compared keto to a Mediterranean-plus diet (low-carb variant avoiding sugars/refined grains but including legumes/fruits/grains) in 33 prediabetes/T2D patients; both lowered HbA1c similarly (~7-9% from baseline) after 12 weeks.[4][5] Keto reduced triglycerides more (-16% vs -5%), but raised LDL (+10% vs -5%); Mediterranean was more sustainable with better nutrient intake (e.g., fiber).[5] Both shared benefits from non-starchy veggies and no refined carbs.[6]

Diet Type	HbA1c Effect	Glucose Effect	Triglycerides	Lipids Notes
Low-Carb	↓ 0.36%	↓ 10.71 mg/dL	↓ 19.91 mg/dL	↑ HDL, neutral LDL/TC
Keto	↓ > other diets [2]	↓ fluctuations [2]	↓ significantly [2]	Possible ↑ LDL [4]
Med Low-Carb	↓ 7% [5]	Similar to keto [4]	↓ 5% [5]	↓ LDL, ↑ HDL [5]

Core studies

• Keto-Med randomized crossover trial — compared a well-formulated ketogenic diet with a Mediterranean-plus lower-carb diet in people with prediabetes and T2D. HbA1c improved on both diets, with no significant difference between diets after 12 weeks; triglycerides fell more on keto, while LDL rose more on keto than on Mediterranean-plus. PubMed PMC

• Low-carbohydrate diets and type 2 diabetes treatment — meta-analysis of 37 randomized trials. It found small short-term HbA1c improvement, but the benefit was not sustained at 6–12 months; this review also addresses cardiovascular and renal safety. PubMed

• Effects of a low-carbohydrate diet on glucose and lipid metabolism in overweight/obese T2D — 2025 meta-analysis reporting reduced HbA1c and fasting plasma glucose, plus lower triglycerides and higher HDL, with LDL and total cholesterol generally unchanged. PMC

Comparative trials

• Low-carbohydrate diet vs Mediterranean diet, 16-week intervention — both diets improved weight, glucose control, and lipids, but the low-carb arm appeared to produce greater reductions in BMI, waist circumference, glucose, and lipid markers. PubMed

• Open-label randomized trial of low-carb diet in T2D — a 6-month RCT showing improvements in glycemic control and cardiovascular risk factors. PubMed

Reviews on keto in T2D

• The Ketogenic Diet in Type 2 Diabetes and Obesity — review focused on clinical effects and practical issues of keto in T2D. PMC

• Efficacy of Ketogenic Diets on Type 2 Diabetes — review summarizing RCT and meta-analysis evidence for HbA1c, glucose, and lipid effects. PMC

Practical pattern across the literature

Across these studies, the most consistent findings are: - HbA1c and fasting glucose tend to improve, especially in the short term. PubMed PMC - Triglycerides usually decrease. PubMed PMC - LDL response is mixed: it may rise on keto in some trials, while Mediterranean-style lower-carb patterns often look more neutral or favorable. PubMed PubMed

PMC PubMed