A ketogenic diet can improve insulin resistance, but the benefit appears to come primarily from the weight loss it produces rather than from ketosis itself. That distinction matters because it shapes how you think about keto compared to other dietary approaches and whether it’s worth the trade-offs for your situation.
How Keto Affects Insulin Resistance
When you eat fewer than 20 to 50 grams of carbohydrates per day, your insulin levels drop significantly. With less insulin circulating, your body shifts to burning stored fat for fuel and produces molecules called ketones as an alternative energy source. Early research painted an optimistic picture: one study found that just six days on a ketogenic diet reduced fasting insulin by 53% and improved a standard measure of insulin resistance (HOMA-IR) by 57% in people with fatty liver disease. Fasting blood sugar dropped 13% in that same period.
Those numbers are striking, but they come with an important caveat. Much of that rapid improvement reflects the immediate effect of simply eating fewer carbohydrates, not a lasting change in how sensitive your cells are to insulin. When researchers tested this more carefully, the results told a different story.
Weight Loss Is the Key Driver
A 2024 study published in BMJ Open Diabetes Research & Care specifically asked whether ketosis improves insulin sensitivity independent of weight loss. Researchers put obese adults with type 2 diabetes on a ketogenic diet for 10 days while keeping their body weight stable. Using the gold-standard measurement for insulin sensitivity (a euglycemic insulin clamp), they found absolutely no change in muscle, liver, or fat tissue sensitivity to insulin. Blood sugar control didn’t improve either.
The researchers’ conclusion was direct: in the absence of weight loss, a ketogenic diet does not improve glycemic control or insulin sensitivity. This finding reframes much of the earlier keto research. Many studies showing dramatic improvements in insulin markers didn’t control for weight loss, so the benefits they reported were likely driven by participants losing fat, not by being in ketosis.
A meta-analysis of randomized controlled trials in overweight patients with type 2 diabetes reinforced this point. When comparing keto to other diets, there were no significant differences in fasting insulin or HOMA-IR between groups. Both approaches improved insulin resistance to similar degrees, suggesting it’s the calorie deficit and resulting weight loss doing the heavy lifting.
What the Blood Sugar Numbers Show
Even if ketosis itself isn’t the magic ingredient, keto diets do reliably lower blood sugar markers, likely because cutting carbohydrates reduces the glucose load your body has to process. A randomized clinical trial of 150 adults published in JAMA Network Open found that a low-carbohydrate diet reduced HbA1c (a three-month average of blood sugar) by 0.23% more than a usual diet over six months. That’s a modest but meaningful reduction, roughly in line with what some oral diabetes medications achieve.
Longer-term data from two-year studies shows that people who stick with a ketogenic diet maintain improvements in insulin resistance markers at both the one-year and two-year marks. However, in one of those studies, participants on a different diet achieved similar reductions in insulin resistance over the same period. The consistency of improvement over two years is encouraging, but it again points to sustained weight management as the underlying mechanism.
Why Keto Still Works for Many People
None of this means keto is a bad choice for insulin resistance. It means the reason it works is more straightforward than the marketing suggests. Keto diets are effective for many people because they naturally reduce appetite, make it easier to eat fewer calories, and produce reliable weight loss. For someone with insulin resistance, losing even a moderate amount of body fat can meaningfully improve how well your cells respond to insulin.
The practical advantage of keto over other diets is that cutting carbohydrates directly lowers the amount of glucose entering your bloodstream after meals. If you have insulin resistance, your body struggles to clear glucose efficiently, so reducing the incoming load gives your system less work to do. This can produce noticeable improvements in how you feel, your energy levels, and your blood sugar readings within the first week or two.
Clinical protocols typically target 20 to 25 grams of net carbohydrates per day, with about 60% to 75% of calories coming from fat and moderate protein. That level of restriction is what reliably produces ketosis.
Risks Worth Knowing About
If you take medications that lower blood sugar, starting a keto diet requires careful coordination with your prescriber. Keto reduces blood glucose so effectively that medications dosed for a higher-carb diet can push your blood sugar dangerously low. This applies to insulin, sulfonylureas, and similar drugs. Doses often need to be reduced or discontinued entirely once carbohydrate intake drops.
SGLT2 inhibitors (a class of diabetes medication) carry a specific risk when combined with keto: they can trigger diabetic ketoacidosis, a dangerous buildup of ketones in the blood. The American Society of Clinical Endocrinology recommends stopping these drugs before starting a ketogenic diet. Metformin, by contrast, does not carry the same hypoglycemia risk and is generally considered compatible with low-carb eating.
Cholesterol changes on keto vary widely between individuals. Some people see improvements in their lipid profiles, while others experience significant increases in LDL cholesterol. If you have insulin resistance alongside cardiovascular risk factors, monitoring your lipids after starting keto is important.
How Keto Compares to Other Approaches
Because weight loss is the primary driver of improved insulin sensitivity, any dietary pattern that helps you lose fat and maintain that loss will produce similar benefits. Mediterranean diets, moderate low-carb diets, and even conventional calorie-restricted diets all improve insulin resistance when they result in sustained weight loss. The best diet for insulin resistance is the one you can actually follow long-term.
Where keto has a distinct short-term advantage is in lowering blood sugar quickly, since you’re simply eating very little glucose. This can be motivating early on and may be especially useful if your blood sugar levels are high enough that rapid improvement matters. But for long-term insulin sensitivity, the trajectory of your body weight matters more than whether you’re in ketosis.