If you have type 2 diabetes, you’ve probably heard conflicting advice about what to eat. Should you cut carbohydrates or cut fat? A randomized trial from Denmark compared the two approaches head to head and found that a low-carb diet had an edge for blood sugar and weight, but only while people kept it up.
How the study worked
The trial, published in the Annals of Internal Medicine, included more than 100 adults with type 2 diabetes. They were randomly assigned to one of two eating plans for six months:
- Low-carb, high-fat: about 20% of calories from carbohydrates, 50–60% from fat and 20–30% from protein.
- High-carb, low-fat: about 50% of calories from carbohydrates, with the rest split between fat and protein.
Both groups ate enough calories to match their energy needs. Calories weren’t restricted, which makes the comparison about the type of food rather than eating less. Researchers then checked in again three months after the diets ended.
What they found
- Better blood sugar control. Hemoglobin A1c, a measure of average blood sugar over about three months, dropped by about 0.6 percentage points more in the low-carb group.
- More weight loss. The low-carb group lost about 8.4 pounds (3.8 kg) more on average.
- Less body fat. The low-carb group also lost more body fat and more inches around the waist.
- Some benefits for both. Both diets raised “good” HDL cholesterol and lowered triglycerides.
- The advantages faded. Three months after the study ended, the differences between the groups were no longer meaningful, likely because many people drifted back to their old eating habits.
Why this matters
Type 2 diabetes affects hundreds of millions of people worldwide, and more than 37 million Americans have diabetes. Many also have fatty liver disease. Losing weight and lowering blood sugar can help with both. This study suggests that reducing carbohydrates can be an effective tool, but that the best diet is one you can stick with over the long run.
It’s also worth noting what the study didn’t show. It wasn’t designed to test very low-carb “keto” diets, and it didn’t follow people for years. Other research has found that many different eating patterns, including Mediterranean-style and plant-based diets, can improve blood sugar when they lead to weight loss and better food quality.
What this means for you
- Talk to your care team before making big changes. If you take insulin or certain diabetes pills, cutting carbs quickly can cause low blood sugar. Your medications may need adjusting.
- Choose quality carbs. Whatever approach you take, favor vegetables, legumes, whole grains and fruit over refined grains, sweets and sugary drinks.
- Choose healthy fats. If you eat more fat, focus on olive oil, nuts, seeds, avocado and fish rather than processed meats and butter.
- Think long term. Pick an eating pattern you can enjoy and maintain. A registered dietitian or diabetes educator can help you build one.
- Track your progress. Regular A1c tests and home glucose checks show how changes are working.
The bottom line
A low-carb diet improved blood sugar and weight more than a low-fat diet over six months in people with type 2 diabetes, but the benefits faded once people stopped. The right plan is a safe one, planned with your care team, that you can keep up.
This article is for general information and isn’t medical advice. Talk with your healthcare provider about your individual needs.
