Can a ketogenic (keto) or low‑carbohydrate diet cause type 2 diabetes mellitus?

Can a Keto/Low Carb Diet Cause Type 2 Diabetes?

No, a ketogenic or low-carbohydrate diet does not cause type 2 diabetes in people without the disease, but the evidence shows concerning associations and metabolic effects that warrant caution.

Key Evidence on Low-Carb/Keto Diets and Diabetes Risk

Epidemiological Findings

The most robust epidemiological evidence comes from a large prospective study showing that higher ketogenic ratio values are associated with increased risk of developing type 2 diabetes 1. In postmenopausal women followed for nearly 18 years, those in the highest quintile of ketogenic ratio had a 24% increased risk of developing type 2 diabetes compared to the lowest quintile (HR 1.24,95% CI 1.18-1.31) 1. Notably, virtually no participants (0.01%) actually consumed a true ketogenic diet, suggesting these findings reflect higher-fat, lower-carb patterns rather than strict ketosis 1.

Acute Metabolic Effects

Short-term metabolic studies reveal concerning physiological responses:

• Severe hepatic insulin resistance develops within just 3 days of ketogenic diet feeding, more pronounced than with obesogenic high-fat diets 2. This manifests as impaired suppression of hepatic glucose production by insulin, even though peripheral glucose uptake remains intact 2.

• Without weight loss, ketogenic diets provide no metabolic benefit. A controlled 10-day study maintaining stable body weight showed that ketogenic diets (with or without ketone supplementation) failed to improve glucose tolerance, insulin sensitivity in muscle/liver/adipose tissue, lipid profiles, or blood pressure 3.

Current Guideline Recommendations

American Diabetes Association Position

The most recent ADA guidelines (2025) acknowledge that low-carbohydrate and very-low-carbohydrate eating patterns can reduce A1C and medication needs in people who already have type 2 diabetes, but only in the short term (<6 months) 4. However, they explicitly state multiple contraindications and cautions:

• Very-low-carbohydrate diets are not recommended for pregnant/lactating women, children, people with kidney disease, those at risk for disordered eating, or anyone taking SGLT2 inhibitors (due to ketoacidosis risk) 4
• Medical oversight is mandatory with frequent medication adjustments needed to prevent hypoglycemia 4
• Long-term effects beyond 6 months show diminishing benefits 5

Macronutrient Distribution Guidance

There is no single ideal macronutrient distribution for diabetes prevention or management 5, 6. The 2018-2019 ADA guidelines emphasize that macronutrient distribution should be individualized, but they consistently recommend:

• Carbohydrate intake from vegetables, fruits, legumes, whole grains, and dairy products 5
• Emphasis on high-fiber foods (minimum 14 g fiber/1,000 kcal) 4, 6
• The recommended dietary allowance for carbohydrate is 130 g/day, making diets restricting below this level not recommended 7, 8

Evidence for Higher-Fiber, Higher-Carbohydrate Approaches

A 2025 meta-analysis directly comparing dietary patterns found that higher-fiber, higher-carbohydrate diets are superior to lower-carbohydrate, lower-fiber diets for diabetes management 9. This challenges the low-carb paradigm by demonstrating that when fiber intake is adequate, higher carbohydrate intake improves outcomes 9.

Clinical Algorithm for Dietary Recommendations

For Diabetes Prevention:

1. Prioritize weight loss of ≥5% through calorie reduction and lifestyle modification 5, 6
2. Focus on dietary pattern quality rather than macronutrient ratios: Mediterranean-style, DASH, or plant-based patterns all reduce diabetes risk 6
3. Ensure adequate fiber intake (≥14 g/1,000 kcal) from whole grains, legumes, fruits, and vegetables 6
4. Avoid very-low-carbohydrate approaches (<130 g/day) as they eliminate important nutrient sources and lack long-term safety data 7, 8

For Existing Type 2 Diabetes:

1. Short-term low-carb diets (3-6 months) may be considered if the patient desires this approach and has no contraindications 4, 5
2. Screen for absolute contraindications: pregnancy, lactation, childhood, kidney disease, SGLT2 inhibitor use, disordered eating risk 4
3. Implement intensive medical monitoring with frequent medication adjustments 4
4. Transition to sustainable higher-fiber pattern after initial period, as long-term low-carb benefits are not maintained 5, 9

Critical Caveats

The hepatic insulin resistance induced by ketogenic diets is a physiological concern that may explain the epidemiological associations with increased diabetes risk 2. While this effect is reversible with carbohydrate reintroduction, chronic exposure to this metabolic state in susceptible individuals could theoretically contribute to diabetes pathogenesis 2.

Weight loss confounds most low-carb diet studies. When weight is held constant, ketogenic diets show no metabolic advantage 3. This suggests that any benefits observed in free-living studies result from calorie restriction and weight loss, not from carbohydrate restriction per se 3.

The quality of carbohydrate matters more than quantity. Guidelines consistently emphasize that refined carbohydrates and added sugars should be minimized, while fiber-rich whole food sources of carbohydrate are protective 5, 4, 6.