Keto and diabetes: Evidence on benefits emerging, but questions remain

Few dietary approaches have generated as much controversy as the ketogenic diet. Proponents point to dramatic improvements in blood glucose control and diabetes remission, weight loss and even psychiatric benefits. Critics raise concerns about long-term sustainability, potential cardiovascular effects and the current lack of long-term randomized data.“Keto diets are high in fat and very low in carbohydrate intake, which lead to nutritional ketosis as a result of increased fat oxidation,”said Dr. David Lau, an endocrinologist and professor of medicine at the University of Calgary who co-chaired the Canadian Adult Obesity Clinical Practice Guidelines, in an email interview. “That can also lead to reduced appetite and hence spontaneous restriction in caloric intake.”A 2026 review published in Nutrients found growing evidence that ketogenic diets can improve glycemic control, reduce body weight and improve insulin resistance in people with obesity and type 2 diabetes. The Polish authors noted that studies have consistently demonstrated improvements in blood glucose levels, HbA1c and weight. They said the diet shows promise in preventing type 2 diabetes but that current clinical evidence is not strong enough to confirm its preventive effects.The study did confirm that short-term use of the keto diet effectively reduces body weight and visceral fat, mainly by decreasing appetite. “In people with obesity, it can also reduce inflammation, improve cardiovascular markers, and help regulate the menstrual cycle. However, long-term use can lead to nutritional deficiencies, particularly calcium, which can adversely affect bone health and therefore require individualized dietary planning and appropriate supplementation,” the authors wrote.Similarly, a 2025 review in Precision Nutrition concluded that the diet may offer short-term benefits for glycemic control and weight loss with the benefits appearing to be particularly notable among patients without significant comorbidities.The study found that by sharply reducing carbohydrate intake, ketogenic diets help reduce blood sugar spikes after meals and decrease the body's need for insulin. For patients with type 2 diabetes, this often translates into improved glycemic metrics and, in some cases, reduced medication requirements.Dr. Jason Fung, a Toronto nephrologist known for his work on intermittent fasting and low-carbohydrate approaches to type 2 diabetes, said in an email interview that the studies are promising and that ketogenic diets are generally safe for most people with obesity or type 2 diabetes because there is no biological requirement for dietary carbohydrates.“The best evidence exists for the ketogenic diet in weight loss and also for type 2 diabetes. There is strong emerging data about its role in psychiatry as well," said Dr. Fung. "Ketogenic diets and low carb approaches are basically low insulin diets. They are most effective in conditions characterized by hyperinsulinemia, such as obesity and type 2 diabetes. Most physicians misunderstand that there is a very strong scientific rationale for its use and clinical evidence of benefits.”But some studies show those benefits may be short-term.Another 2025 review of low-carb diets for type 2 diabetes found that while carb restriction can produce modest metabolic benefits in the short term, those advantages often diminish over time. The Thai authors concluded that low-carbohydrate diets can be effective tools for diabetes management, but long-term success depends heavily on adherence and individualized care.Read: Which is better for weight loss and hypertension: Keto or the Mediterranean diet?These findings reflect a central debate around keto diets and diabetes. While improvements in blood sugar control are well-documented, researchers continue to ask whether the benefits stem from ketosis itself or from more general effects of weight loss, calorie reduction and decreased intake of refined carbohydrates.Dr. Lau, an obesity expert caring for patients living with overweight and obesity, believes the benefits are simply reflective of the calorie restriction and weight loss.“Ketogenic diets are best understood as one member of a broader class of energy-restricted, carbohydrate-restricted dietary patterns—alongside Mediterranean, DASH, plant-based, and standard calorie-restricted diets,” said Dr. Lau.“Short-term studies (less than 12 months) show benefits in weight loss, lower HbA1c and improved glucose control, as well as improved triglyceride levels. Longer-term data (one to two years) fail to demonstrate superiority in weight loss compared with other calorie-reduced diets and (demonstrate) difficulty with adherence to keto diets.”Dr. Lau also pointed out there are particular concerns with keto diets:Elevation of bad (LDL) cholesterol levels and potentially increased cardiovascular disease risks in some patientsLow dietary fibre and nutritional deficiencies, especially micronutrientsLack of long-term data on benefits in weight loss and glycemic controlHe noted that keto diets are not recommended in the following populations:Pregnant or breastfeeding womenPatients with advanced kidney disease (needs monitoring)Patients with history of eating disordersAthletes requiring high-intensity performancePeople unable to sustain restrictive diets“Mediterranean, DASH and MIND (Mediterranean-DASH-Intervention for Neurodegenerative Delay) diets are by far superior to keto diets with respect to weight loss, improved cardiometabolic benefits, improved blood sugar—and without any safety concerns with keto diets,” Dr. Lau said. “I would not recommend diets that offer little benefits but are potentially harmful, even for the short term. Keto diets may offer slightly more weight loss than the healthier Mediterranean diet, but they’re difficult to adhere to and when people revert to their usual diets, weight regain will recur.” Long-term safety remains an active area of medical investigation. Concerns persist regarding dietary quality, cardiovascular risk with a high-fat diet and the practicality of maintaining a restrictive diet over months or years, with authors calling for longer-term trials to determine whether early improvements translate into sustained reductions in or control of diabetes.For now, the consensus appears to be that ketogenic diets can be an effective option for some patients with type 2 diabetes. The larger question is not whether keto can work, but for whom it works best, how long the benefits last and whether they can be achieved through other, less restrictive approaches.“I think it is important to remind our patients living with obesity that there are no quick fixes for weight loss,” said Dr. Lau.

Keto and diabetes: Evidence on benefits emerging, but questions remain

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