A person with prediabetes has blood sugar levels that are high but not yet within the ranges of diabetes. There is still time to control the levels and prevent diabetes from developing.

Worldwide, around 5–10% of people with prediabetes develop diabetes each year. Up to 70% of people with prediabetes go on to develop diabetes, according to research from 2012.

Taking preventive action, such as making dietary changes, can reduce this risk by 40–75%. Indeed, 5–10% of people with prediabetes return to normal glucose levels each year, the study suggests.

If a person with prediabetes knows what action to take, there is a good chance that they can prevent diabetes from developing.

Prevention plans usually involve two key lifestyle factors: a healthful diet and regular exercise.

This article will discuss how diet and prediabetes are related and provide some diet tips for managing glucose levels.

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Results of the Diabetes Prevention Program in the United States suggest that in people with overweight, every 2.2 pounds (1 kilogram) they lose per year can reduce their risk of developing diabetes by 16%.

After 3 years, this would be equal to a 58% reduction in risk.

A diet that can help a person lose weight and manage prediabetes will normally include foods that are:

People should eat plenty of:

  • vegetables
  • whole grains
  • lean meats
  • protein-packed legumes

They should be careful to avoid added sugars. Fruits contain sugar, but they also provide fiber and other nutrients. For this reason, a person can include a limited amount of fruit in their diet.

The glycemic index (GI) is a useful tool for measuring types of carbohydrates and for choosing those that are healthful. It is based on how quickly sugar from food will enter the person’s bloodstream.

People with diabetes need to be mindful of their carb, and especially added sugar, intake.

However, a food that contains carbs or sugar is not always bad. For example, fruits contain natural sugars, and whole grains are high in carbs, but they also provide fiber and other nutrients. This makes them suitable, in moderation, for a person who is following a prediabetes diet.

The GI is an index, or list, of foods. It ranks foods according to the rate at which they affect blood sugar levels. The highest score is 100, and the lowest is 0.

It does not measure amounts of anything, but it compares the ways that foods cause sugar levels to rise in the blood, with 100 being the top level.

Some foods that cause blood sugar to spike exceptionally high may have a value above 100. For example, russet potatoes score 111 on the GI.

Sample GI values

Here are some more sample values:

  • fruit roll-ups: 99
  • plain white baguette: 95
  • whole grain bread: 51, depending on the type
  • cornflakes: 93
  • muesli: 66
  • natural oatmeal: 55, on average
  • white rice: 89
  • brown rice: 50
  • full fat milk: 41
  • skim milk: 32
  • watermelon: 72
  • banana: 62
  • apple: 39
  • unsweetened apple juice: 42
  • white spaghetti: 58
  • wholemeal spaghetti: 42
  • baked beans: 40, depending on the brand

The carb levels will also vary depending on the individual item. Some apples, for example, are sweeter than others. Manufacturers may also use different ingredients in their products.

One study shows the values, with variations. The researchers fixed these values in 2008, and they review them from time to time.

What makes a low or high GI score?

The body digests whole grains and high fiber foods slowly. Their sugars enter the bloodstream gradually. Foods that contain fiber, such as fruits and whole grains, will have a lower GI score than those made with refined ingredients.

The body processes sugars and refined carbs quickly. This causes a quick rise in blood sugar levels and a “sugar spike,” or high glucose levels in the blood. Foods containing refined carbs and added sugars will have a high GI score.

This is why white bread has a higher GI value than wholemeal bread.

People with prediabetes should try to avoid a sugar spike. Here are some tips that may help:

  • Foods with a GI score of 55 or under raise blood sugar levels slowly.
  • Foods with GI scores between 56 and 69 raise blood sugar levels at a moderate rate.
  • Foods with a GI score of 70 or above raise blood sugar levels rapidly.

Some GI tips

It is not easy to tell a food’s GI score simply by looking at it.

Here are some tips that may help:

  • Foods that contain refined sugars usually have a higher GI score than foods that contain natural sugars, such as fruit.
  • Whole foods tend to have lower GI scores than products made with refined grains, such as white bread or rice.
  • Sweet potatoes, most vegetables, whole fruit, and legumes have lower GI scores than white starchy vegetables, such as potatoes.
  • As most fruits and vegetables ripen, their sugar content increases and their GI score goes up.
  • Pastas tend to have low GI scores due to the way their starches are bound.
  • Parboiled rice, basmati rice, and brown rice all have lower GI scores than short grain or jasmine rice.
  • Homemade oatmeal or stone-cut oats have lower GI scores than packaged oatmeal.

Researchers have not confirmed, however, whether following a low GI diet will help all individuals manage prediabetes. It is best to ask a doctor or dietitian for advice that suits one’s situation.

Some people find that counting carbs helps ensure that they get an appropriate amount in their diet.

Indeed, cutting out carbs altogether is not necessarily healthful. Some high carb foods, such as potatoes and peas, offer other nutritional benefits.

However, many low carb foods can provide the same nutrients. Swapping high for low carb choices can be an easy way to reduce carb intake.

For example, the following starchy vegetables are high in carbs:

  • potatoes
  • peas
  • corn

When eating these carbs, it is important to control portions to avoid a spike in blood sugar. One cup of potatoes, peas, or corn contains about 30 grams of carbohydrates.

The following vegetables have fewer carbs per portion and are rich in fiber and other nutrients:

  • asparagus
  • broccoli
  • carrots
  • celery
  • green beans
  • lettuce other salad greens
  • peppers
  • spinach
  • tomatoes
  • zucchini

The Institute of Medicine suggest that 45–65% of a person’s diet should consist of carbs.

People with prediabetes need to keep their blood sugar levels as steady as possible.

Fasting can cause significant changes in blood sugar levels, but eating small meals at regular intervals can help maintain glucose levels.

Experts recommend eating three properly portioned meals regularly throughout the day. These meals should be no more than 6 hours apart.

They also suggest ensuring that meals are balanced, with each containing a source of protein, fat, and carbs.

To check whether or not a meal is correctly portioned, a person might use the plate method.

The United States Department of Agriculture (USDA) recommend that each meal should consist of:

  • one-half fruits and vegetables
  • just under one-quarter meat, fish, or another protein equivalent
  • just over one-quarter carbs, such as whole grains
  • a serving of dairy on the side

Some research suggests that having smaller portions may help people lose weight, but more research is needed to verify this.

Health authorities, including the National Institutes of Health (NIH), recommend following the Dietary Approaches to Stop Hypertension (DASH) diet for better health. Combined with carb counting and an awareness of the GI scores of various foods, it can help people with prediabetes.

This diet focuses not on eating fewer calories but on making more healthful choices.

It encourages people to eat:

  • vegetables
  • fruits
  • whole grains
  • fat-free or low fat dairy products
  • fish
  • poultry
  • beans
  • nuts
  • vegetable oils

People should avoid foods that are high in saturated fats and sugar, such as:

  • fatty meat
  • full fat dairy products
  • coconut, palm, and other tropical oils
  • candy
  • sugary drinks

Learn more about the DASH diet here.

Having prediabetes does not mean that a person cannot eat out or enjoy their food, but they do need to be mindful about the choices they make.

Here are some tips for eating out:

  • Encourage friends and family to eat at restaurants that have healthful options.
  • Choose a salad and ask to have it without dressing, or ask for a little olive oil or lemon juice to dress it with.
  • Avoid buffets if it is too tempting to have more than one plate.
  • Go for quality, such as fresh ingredients, rather than quantity.
  • See if the menu lists the calories for each dish.
  • Opt for sparkling water with ice and a slice of lemon, instead of soda or alcohol.

If a person has just received a diagnosis of prediabetes, they may be wondering what they can eat.

Here are some suggestions for meals to eat throughout the day:

MealWhat to eatWhat to avoid
BreakfastRolled or whole oats

Wholemeal bread

Whole peanut butter without added sugar

Fruit

Up to 4 ounces of 100% fruit juice with no added sugar

Coffee or tea with low fat milk and no sugar
White bread and bagels

Sweetened breakfast cereals

Sweetened juices

“Specialty” coffees from coffee shops, as these contain sugar
LunchBaked beans on wholemeal toast

Brown rice, lentils, and salad with a little olive oil

Homemade vegetable soups

An apple or pear, or a cup of melon or berries
Bagels, baguettes, and other white or refined breads

Burgers and many fast food items

Salad dressings and ketchup with added sugar
DinnerYam or sweet potato with chicken, broccoli, and asparagus

Wholemeal pasta with homemade tomato sauce and salad

For dessert, fruits and ice-cream made with fruit and yogurt without added sugar
Pizza

Ready made sauces

Fatty meats
SnackNuts

Fruit

Low fat natural yogurt
Candy

Ready made “health” bars, unless the details on the label show that they are very low in added sugar

Fruit, in moderation, is highly nutritious. It contains fiber, water, vitamins, and minerals.

To lower the impact on blood sugar and keep one full for longer, people can enjoy fruit with a protein or healthy fat, such as nut butter, a small handful of nuts seeds, or avocado.

People can check with a doctor or dietitian about how much of their favorite items are appropriate to consume.

People should try to balance out their carb intake throughout the day, to avoid sugar spikes. For example, eating a lot of sweet foods for breakfast and then avoiding them for the rest of the day will not help.

Alcohol consumption can increase weight and the risk of diabetes.

One study suggests that “risky” alcohol use in males significantly raises their chance of developing diabetes.

Limiting or avoiding alcohol consumption can help a person control their blood glucose levels and contribute to weight loss.

If consuming alcohol, be sure to avoid sugary mixers such as soda.

Diet alone may not prevent prediabetes from developing into diabetes. Some other strategies to try include exercise and medication.

Exercise

Physical activity can help a person lose weight and control their blood sugar levels. Exercise uses up excess blood sugar for energy and can improve insulin sensitivity.

At least one study suggests that making dietary changes and getting more exercise are effective at preventing the progression to diabetes.

A 2011 article recommends that people with prediabetes do 210 minutes of moderate intensity exercise, or 125 minutes of vigorous intensity exercise, each week.

For people with type 2 diabetes, the American Diabetes Association recommend that during prolonged sitting, they should get up every 30 minutes for some light walking or resistance training. This can help reduce blood glucose levels.

Regular activities that may help include:

  • swimming
  • brisk walking
  • running
  • strength training
  • flexibility training

Housework, gardening, and other activities can all contribute.

Medications

For some people with prediabetes, a doctor may prescribe metformin to help control blood sugar levels.

This can help, but it does not appear to be as effective as certain lifestyle measures, and, like all drugs, metformin can have side effects.

For this reason, doctors encourage most people to use lifestyle measures as far as possible.

One 2015 study suggests that U.S. physicians prescribe the drug metformin for fewer than 4% of people with prediabetes.

Experts remain undecided as to whether or not metformin is helpful for people with prediabetes, or if lifestyle measures should be the primary focus at this stage.

RECALL OF METFORMIN EXTENDED RELEASE

In May 2020, the Food and Drug Administration (FDA) recommended that some makers of metformin extended release remove some of their tablets from the U.S. market. This is because an unacceptable level of a probable carcinogen (cancer-causing agent) was found in some extended-release metformin tablets. If you currently take this drug, call your healthcare provider. They will advise whether you should continue to take your medication or if you need a new prescription.

Prediabetes can develop into diabetes if a person does not take care with their diet and exercise regimen.

With early action, a person has a good chance of preventing the development of a more serious condition in the future.

There is no one-size-fits-all diet for prediabetes. Anyone who receives a diagnosis of this condition should ask their doctor for advice.