Low-Carbohydrate and Ketogenic Diets for Prediabetes
Low-carbohydrate diets have gotten a lot of attention recently as strategies for reversing prediabetes (impaired glucose tolerance). The carbohydrates in your diet that provide calories include sugars and starches. Starches are in grains and flour, beans, and starchy vegetables. Added sugars include sugars in sweets, sweetened foods such as flavored oatmeal and ketchup, and sugar-sweetened beverages such as soda, which can be dangerous if you are insulin sensitive. There are also natural sugars, which are found in nutritious foods such as dairy products and fruit.
Proponents of low-carbohydrate weight loss diets, such as Atkins, claim that the diet can help you lose weight because instead of burning dietary carbohydrates for fuel, you burn body fat because you are eating so few dietary carbohydrates. The diet can help you cut calories by:
Eliminating or severely restricting high-calorie foods such as sweets and refined carbohydrates.
Promoting satiety by increasing protein and fat, which are filling nutrients.
Reducing appetite by reducing the food choices available to you.
Sugars and starches that you get from your diet enter your bloodstream as a type of sugar called glucose. In prediabetes, your body has trouble managing the glucose in your blood due to resistance to a hormone called insulin, which can lead to a risk of developing type 2 diabetes. Normally, insulin is able to help your body keep blood glucose levels in check, but the effect is weaker if you have impaired insulin resistance, so blood glucose rises.
There is research supporting reduced-carbohydrate diets in the treatment of prediabetes. Reducing your sugar and starch intake may lower blood sugar levels by preventing as much sugar from going into your blood. It can also help reverse insulin resistance.
Reduced-carbohydrate diets range from moderate to very low-carb. The rest of your calories come from protein and fat, so you might depend more heavily on high-protein and high-fat foods than the average person.
Low-Carb and Ketogenic Diets for Prediabetes
Foods to Emphasize
- Meat, poultry, and fish
- Non-starchy vegetables
- Full-fat cheese and yogurt
- Nuts and seeds
- Fresh fruit, especially berries
- Beans, peas, and lentils
Low Carb Foods
Moderate Carb Foods (Low-Carb Diet)
- Has been shown to lower insulin resistance and blood glucose levels (A1c) among individuals with diabetes and prediabetes.
- Can aid in weight loss due to:
- Calorie reduction from eliminating sweets and other high-calorie foods.
- Increased fullness from protein and fat.
- Reduced appetite from limited food choices.
- Can be simpler to follow since food choices are more “black or white” – off limits or allowed.
- Avoids unhealthy processed, sugary, and fried foods.
- Avoiding sugars and starches can help some people avoid sugar cravings.
Foods to Limit or Avoid
- Fruit juice and dried fruit
- Most fruit (esp. ketogenic diet)
- Starchy vegetables (e.g., peas, winter squash, corn, and sweet potatoes)
- Beans, peas, and lentils (esp. ketogenic diet)
- Reduced-fat dairy products, including sweetened yogurt (esp. ketogenic diet)
- Grains (e.g., bread, pasta, rice, cereal, oatmeal, crackers, and pretzels)
- Processed snack foods, such as potato chips, tortilla chips, and
- Fried foods, such as doughnuts, French fries, and fried chicken.
- Sweets (e.g., candy, cake, ice cream, pie, pastries, and cookies)
- Sugar-sweetened beverages (e.g., soft drinks, energy drinks, sugar-sweetened coffee and tea, and sports drinks)
- Alcoholic beverages
Difficult to limit carbohydrates so much.
- They taste good.
- They are in many common foods.
- Lack of long-term data on health outcomes:
- Is the high protein content tough on kidneys and the liver?
- Is it really healthy to give up nutrient-dense foods such as whole grains, legumes, and fruit, which are linked to lower risk for certain diseases, include heart disease and even diabetes?
- Potentially low in fiber, which aids with fullness, blood sugar control, and heart health.
- Will you regain weight and reverse health benefits if you add carbs back into your daily menu?
- Difficulty in following the diet long-term:
- What will you eat at restaurants and at social events?
- Are you able and willing to give up so many foods…forever?
- Risk of eating too much saturated fat from fatty meat and poultry with skin.
- Can be cumbersome to count grams of carbohydrates.
- Possibility of trouble exercising due to low energy from lack of glycogen, which is the storage form of carbohydrates in your body.
A ketogenic diet is a type of low-carbohydrate diet that is on the extreme end. The goal is to limit carbohydrates so much that the body does not have enough glucose – a type of carbohydrate – to fuel the brain normally. Instead, the body shifts to a metabolic state called ketosis, and produces ketone bodies to fuel the brain’s activities.
The theory behind a ketogenic diet for prediabetes is that when your body is in ketosis, you can be sure that you do not have excess carbohydrates in your diet. Since carbohydrates in your diet are broken down into glucose that goes into your bloodstream, being in ketosis assures that you are not inundating your bloodstream with excessive amounts of glucose due to the foods you eat.
A ketogenic diet might include about 20 to 50 grams per day of non-fiber carbohydrates, or about 5 to 10% of total calories from carbohydrates. The rest of your calories come from fat and protein. The food choices on this diet are similar to those on other low-carb diets, but you may need to further restrict some of the moderate-carbohydrate options that might be easier to fit in on a more moderate low-carb diet. Examples include fruit (an apple has 24 grams of non-fiber carbohydrates) and starchy vegetables (a half-cup of corn has 15 grams of non-fiber grams of carbs).