Pros and Cons of the Keto Diet for People With Diabetes

An ultra-low-carb meal plan like the ketogenic diet may sound like a smart choice for people looking to manage their blood sugar levels. But the buzzy eating pattern may come with consequences, particularly when followed long-term.

Below, experts highlight the pros and cons of the keto diet for people with type 2 diabetes.

Originally used as a therapeutic diet for children with drug-resistant epilepsy, the keto diet has recently gained traction among people looking to shed pounds, manage blood sugar levels and improve cognitive function.

Here's how the ultra-low-carb diet works:

Normally, the body's primary source of fuel is glucose, a sugar that results when you break down carbohydrates. When glucose is in short supply, as is the case on a ketogenic diet, the body must find other sources of energy.

That's where ketosis comes in. Ketosis refers to a metabolic state in which a body starved of carbs instead burns fats in order to generate a new source of fuel, called ketones.

"When there is not enough glucose in the bloodstream to supply the body's processes, the use of ketones for energy serves as a 'back-up,'" says Diana Mesa, RD, CDCES, a registered dietitian, certified diabetes care and education specialist and the founder of the practice En La Mesa Nutrition. The process of creating that 'back up' fuel also requires the body to burn more calories.

Just how low-carb is the keto diet? On average, adults (including those with diabetes) tend to get about 45 percent of their daily calories from carbohydrates, according to an April 2019 consensus report in ‌Diabetes Care‌. On a standard 2,000 calorie-a-day diet, that comes out to about 225 grams of carbohydrates.

A keto diet, on the other hand, calls for just 5 to 10 percent of total calories coming from carbs, or less than 50 total grams of carbohydrates per day, per the Harvard T.H. Chan School of Public Health.

To put that into perspective: Eating one medium apple and one medium banana would put you over the daily carb limit on a keto diet.

Hear this: It is not recommend that anyone follow a keto diet long-term, and that includes people with type 2 diabetes. There is not enough research regarding long-term side effects, and the drawbacks of the diet may outweigh any potential health benefits.

That said, following a keto diet for a short period is likely to promote weight loss and lower blood glucose levels.

Weight management is often a hallmark of type 2 diabetes management. For those with type 2 diabetes and a high body mass index, even a moderate 5 percent weight loss can help improve pancreatic function and insulin sensitivity, according to the American Diabetes Association.

For people looking to shed pounds fast, the keto diet will likely lead to weight loss if followed correctly. When compared to low-fat diets, high-fat ketogenic diets have been shown to produce greater reductions in body weight (both in people with and without type 2 diabetes), per a July 2020 meta-analysis in ‌Nutrients‌‌.‌

There are multiple reasons why the meal plan supports weight loss. "The keto diet usually produces weight loss in the short-term in part due to decreased levels of insulin, increased satiety and potentially decreased calorie intake," says Molly Chanzis, RD, CDCES, a registered dietitian and certified diabetes care and education specialist at Culina Health.

Increased calorie burn thanks to the body's conversion of fat and protein to fuel, as well as lower levels of the 'hunger hormone' ghrelin may also contribute to the keto diet's effects on weight, per the Harvard T.H. Chan School of Public Health.

Yet "although the keto diet often leads to weight loss, it can also contribute to high cholesterol, dehydration, kidney stones and constipation, so the risks and benefits should be weighed carefully," Chanzis says.

Weight loss often coincides with improvements in insulin sensitivity, which is why keto supporters recommend the diet for people looking to manage their blood sugars.

Indeed, a number of studies suggest the keto diet can improve insulin sensitivity and glycemic control in people with type 2 diabetes, per an April 2022 systematic review in ‌Current Diabetes Reviews‌.

Yet whether those positive effects last remains to be seen. Some research suggests that improvements in blood sugar control from very low-carb diets may recede after just three to six months, per a May 2018 paper in ‌Diabetes Research and Clinical Practice‌‌.‌

Experts agree that the drawbacks of a keto diet far outweigh its potential benefits. Here are a few reasons why.

In order for an eating pattern to stick, it needs to be sustainable. And for most people, the keto diet isn't easy to follow for long.

"The ketogenic diet is very restrictive, which can lead to feelings of deprivation, making it tough to stick to," says Jessica Jones, RD, CDCES, a registered dietitian, certified diabetes care and education specialist and the founder of the practice Jessica Jones Nutrition. "It's also extremely difficult to keep up with…in social situations or [when] eating out, and many patients report feeling isolated while on it."

Jones adds that there isn't much long-term research on the efficacy of a ketogenic diet specifically for people with type 2 diabetes, "so we don't really know if it's safe or sustainable for the long haul."

"With the keto diet, you're cutting out many fruits, veggies, legumes and whole grains, which are key sources of fiber, vitamins and minerals," Jones says.

Fiber plays an essential role in diabetes management due to its role in regulating blood sugar levels. "Soluble fiber in particular can slow down glucose absorption in the bloodstream, preventing blood sugar spikes and helping keep them at a steady level," Jones says.

Also important: People with type 2 diabetes are at a markedly greater risk of cardiovascular disease. By minimizing fiber — which helps to decrease LDL cholesterol levels — and maximizing saturated fat — which ‌increases‌ LDL cholesterol levels — the keto diet may actually worsen cardiovascular outcomes in this population if the meal plan is followed indefinitely.

Magnesium is another key nutrient that's primarily found in whole foods, like beans, rice and oats, all of which are limited on a ketogenic diet. "Magnesium plays a role in how insulin works, and eating foods rich in magnesium is important for better blood sugar management," Mesa notes.

Hypoglycemia ranks high on the list of reasons to skip a ketogenic diet if you have type 2 diabetes. Quick reminder: 'Hypoglycemia' refers to dangerously low blood glucose levels that can cause symptoms like feeling shaky, sweaty, confused, dizzy, lightheaded or nauseous and possibly an irregular heartbeat or loss of consciousness if severe enough, per the Mayo Clinic.

Not surprisingly, very-low-carb meal plans like the keto diet are more likely to induce hypoglycemia. And people restricting carbs while simultaneously taking medication to manage their diabetes — especially insulin or a sulfonylurea like DiaBeta, Amaryl or Glucotrol — are at an even greater risk of low blood sugar.

Before starting a ketogenic diet, talk to an endocrinologist or registered dietitian who specializes in diabetes to discuss if and how you may need to modify your medications on this new meal plan.

"There is no one-size-fits-all meal plan for people with type 2 diabetes," Jones says. But the keto diet is one to avoid, because it's risks far outweigh the potential (short-term) benefits.

"It's important to individualize your eating pattern based on your specific health status, access and preferences," Jones says. "I like to encourage people to get a balance of carbohydrates, fats, fiber and protein at most meals so that they can stabilize their blood sugar levels."

Mesa also emphasizes the need for personalization in managing type 2 diabetes, as well as a focus on both sustainability and safety. "Restricting an entire food group may [mean we are limiting] nutrients that would have otherwise been beneficial," she says. "Following a restrictive eating pattern also limits how we interact with the people in our lives at social gatherings and celebrations, especially if you're from a culture where food is the center of every gathering."

If you're looking to optimize your diet for type 2 diabetes management, work with a registered dietitian who can support you in creating a meal plan that's balanced, enjoyable and realistic for you.

Though the terms sound similar, 'ketosis' and 'ketoacidosis' are not one and the same. Think of diabetic ketoacidosis as an advanced, riskier form of ketosis.

Whereas ketosis is the process of burning fat for fuel, "ketoacidosis is a pathological buildup of ketones and glucose, which makes the blood dangerously acidic," says Nina Sundaram, MD, a board-certified endocrinologist and the founder of Aura Endocrinology.

"This can be life-threatening...and may happen when the body is under stress, for example, during sickness or during physical trauma," Mesa says.

Though ketoacidosis can occur in people with type 2 diabetes, it's more commonly seen in people with type 1 diabetes when blood sugar levels are elevated and insulin is in short supply.

While an August 2018 study from ‌The Journal of Physiology‌ suggested that a ketogenic diet may ‌worsen‌ glucose tolerance, there's not much research or consensus to date supporting the idea that keto diets cause diabetes.

It's also worth nothing that that study was short in its duration and conducted in mice, not humans, so the results should be taken with a grain of salt.