Worldwide, 5–10 percent of people with prediabetes develop diabetes each year, and up to 70 percent of people with prediabetes go on to develop diabetes, according to research published in the Lancet in 2012.
Taking preventive action, such as dietary changes, can reduce this risk by between 40 and 75 percent. Indeed, between 5 and 10 percent of people with prediabetes go back to normal levels each year, the study says.
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 healthy diet and regular exercise.
Prediabetes diet: Foods to eat and avoid
Dietary changes can reduce the risk of prediabetes progressing to diabetes.
Results of the Diabetes Prevention Program in the United States have suggested that, in people who are overweight, each 2.2 pounds (1 kilogram) they lose in a year can reduce their risk of developing diabetes by 16 percent.
After 3 years, this would be equal to a 58-percent reduction in risk.
A diet that can help to lose weight and manage prediabetes will normally include foods that are:
- low in fat
- low in calories
- high in fiber
The person should eat plenty of:
- 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 carbs and for choosing those that are healthful. It is based on how quickly sugar from food will enter the bloodstream.
People with diabetes need to take care how much carbohydrate, and especially added sugar, they consume.
However, a food that contains carbs or sugar is not always bad. Fruits contain natural sugars, and whole grains are high in carbs, but they also provide fiber and other nutrients. These make them suitable, in moderation, for a person on 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 food 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. According to the Oregon State University, 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, but check the brand
The amounts of carb will also vary depending on the individual item. Some apples, for example, are sweeter than others, and manufacturers use different ingredients.
A study published in Diabetes Care shows the values, with variations. 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 fruit and whole grains, will have a lower GI 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.
A person with prediabetes needs to avoid a sugar spike.
- foods with a GI value of 55 or less raise blood sugar levels slowly
- those with GI values between 56 and 69 raise blood sugar levels at a moderate rate
- those with a GI value of 70 or above raise blood sugar levels rapidly
Some GI tips
Whole-grain bread and whole peanut butter without added sugar are healthful in moderation.
It is not easy to tell a food's GI value simply by looking at it.
Here are some tips that may help:
- Foods that contain refined sugars usually have a higher GI value than foods that contain natural sugars, such as fruit.
- Whole foods tend to have lower GI values than products made with refined grains, such as white bread or rice.
- Sweet potatoes, most vegetables, whole fruit, and legumes have lower GI values than white starchy vegetables, such as potatoes.
- As most fruits and vegetables ripen, their sugar content increase and their GI value goes up.
- Pastas tend to be low-GI foods because of the way their starches are bound.
- Parboiled rice, basmati, and brown rice all have lower GI values than short-grain or jasmine rice.
- Homemade oatmeal or stone-cut oats have a lower GI count than packaged oatmeal.
However, it is best to ask a doctor or dietitian for advice that suits your situation.
Some people find that counting carbs help to ensure an appropriate amount of carbohydrate.
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.
The following starchy vegetables are high in carbs:
When eating these carbohydrates, 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 have fewer carbs per portion and are rich in fiber and other nutrients:
- green beans
- lettuce other salad greens
The National Institute of Health suggests 45 to 65 percent of a person's diet should consist of carbohydrate.
There are apps available to help you keep track of your carbs. Medical News Today's article on the best apps for diabetes has a link to "Counting with Lenny" and other apps that can help you keep track of your diet.
Eat regular meals
A person with prediabetes needs 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 to maintain glucose levels.
- eating three properly-portioned meals regularly throughout the day, no more than 6 hours apart
- ensuring meals that are balanced, with each containing a source of protein, fat, and carbohydrates
To check whether a meal is correctly portioned, a person might use the plate method.
The plate method
The Diabetes Society recommend that each meal should consist of:
A healthful plate should be one-half vegetable, one-quarter protein food, such as lean meat, and one-quarter carbs, for example, brown rice or quinoa.
- one-half vegetables, at least two servings
- one-quarter meat, fish, or an equivalent
- one-quarter carbs, for example, rice, pasta, bread or potatoes
- a drink of water, low-fat milk, or other healthful options
- a piece of fruit
In addition, each meal should include at least three out of the four key food groups.
The four groups are:
- fruit and vegetables
- grain products, preferably whole grains
- milk or an alternative
- meat, fish, lentils, or an alternative
For people who need or wish to lose weight, studies have found that a using a smaller plate may encourage people to eat less.
The DASH diet
Health authorities, including the National Institutes of Health, recommend following the DASH diet for better health. Combined with carb counting and awareness of the GI, it can help people with prediabetes.
This diet focuses not on eating fewer calories, but on making healthful choices.
People are encouraged to eat:
- whole grains
- fat-free or low-fat dairy products
- 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
- sugary drinks
See MNT's article on the DASH diet to find out more about what to eat and its benefits.
Having prediabetes does not mean that a person cannot eat out or enjoy their food, but they do need to be mindful about choices.
Here are some tips for eating out:
- Encourage friends and family to eat with you 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 a dish.
- Opt for sparkling water with ice and a slice of lemon, instead of soda or alcohol.
If you have just had a diagnosis of prediabetes, you may be wondering what you can eat.
Here are some suggestions for meals throughout the day.
|Meal||What to eat||What to avoid|
|Breakfast||Rolled or whole oats
Whole peanut butter without added sugar
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 cereal
Many "specialty" coffees from coffee shops contain sugar, so check before buying
|Lunch||Baked beans on wholemeal toast
Brown rice, lentils, and salad with a little olive oil
Home-made 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
|Dinner||Yam or sweet potato with chicken, broccoli and asparagus
Wholemeal pasta with home-made tomato sauce and salad
Fruits, ice-cream made with fruit and yogurt without added sugar
|Snack||Nuts, fruit, low-fat, natural yogurt||Candies and ready-made "health" bars, unless the details on the label show they are really low in added sugar|
Fruit, in moderation, is highly nutritious, containing fiber, water, vitamins, and minerals.
To lower the impact on blood sugar and keep you full for longer, enjoy fruit with a protein or healthy fat such as nut butter, a small handful of nuts seeds, or avocado.
Check with a doctor or dietitian how much of your favorite items are appropriate.
You should try to balance out your carb intake throughout the day, to avoid sugar spikes. 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 also the risk of diabetes.
One study has found that "risky" alcohol use in men significantly raised their chances of developing diabetes.
Limiting or avoiding alcohol consumption can help a person both to control their blood glucose levels and contribute to weight loss.
If consuming alcohol, avoid sugary mixers such as soda.
Diet alone may not prevent prediabetes from developing into diabetes. Other strategies include exercise and medication.
Exercise and dietary changes combined can help prevent diabetes.
Physical activity can help a person reduce weight and control their blood sugar levels. Exercise uses up excess blood sugar for energy and can improve insulin sensitivity.
An article published in Exercise and Sports Science Australia recommends that people with prediabetes get 210 minutes of moderate-intensity exercise or 125 minutes of vigorous exercise each week.
The American Diabetes Association recommend 30 minutes of aerobic exercise, such as brisk walking, at least five times per week and preferably every day. One benefit of exercise is that it can help reduce blood glucose levels.
Activities that may help include:
- brisk walking
- strength training
Housework, gardening, and other activities can all contribute. The American Diabetes Association suggest that people who work in a sedentary job should get up and walk around every 30 minutes.
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 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.
A study published in the Annals of Internal Medicine found that American physicians prescribed the drug metformin for fewer than 4 percent of people with prediabetes.
At least one study, published in 2014, has suggested that dietary changes and exercise are effective at preventing the progression to diabetes.
What is prediabetes?
Diabetes and prediabetes are metabolic conditions. Behaviors and health issues that affect the body's ability to metabolize, absorb, or store energy can influence the condition.
Why do blood sugar levels rise?
A doctor will use a blood glucose monitor to check a person's blood sugar levels, but people can also do this at home.
Factors that can cause blood sugar levels to rise include:
- insufficient insulin production
- impaired insulin expression
- the cells not responding properly to insulin
Prediabetes can affect anyone, but some people are more likely to experience it.
Factors that increase the risk include:
- being over the age of 40 years
- having low activity levels
- carrying excess weight
Other factors include:
- family or genetic traits, including having a direct relative with diabetes or being from certain ethnic or racial groups, including Pacific Islanders and African Americans
- having high blood pressure, heart disease, or both
- having high levels of triglyceride and "bad" cholesterol, or high-density lipoprotein (LDL)
- having low levels of "good" cholesterol, known as high-density lipoprotein (HDL)
- having excess belly fat or carrying extra weight around the middle, rather than the hips
- having another specific condition, such as polycystic ovary syndrome (PCOS), gestational diabetes, and low testosterone in men
The symptoms of prediabetes, if there are any, may be hard to spot.
A person may notice:
- increased thirst and urination
- difficulty concentrating
- unexpected weight changes
A darkening of the skin, called acanthosis nigricans, can also occur on various parts of the body, such as the neck, elbows, knuckles, and knees. Everyday wounds may take more time to heal than normal.
People can use a glucose monitor to check their blood sugar levels. These are available for purchase online.
Prediabetes can develop into diabetes if a person does not take care with their diet and exercise regime.
However, by taking the right action, a person with this diagnosis has a good chance of preventing a more serious condition in the future.
There is no one-size-fits-all diet for prediabetes. Anyone who receives a diagnosis should ask their doctor or healthcare provider for advice.