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How to Control Blood Sugar With Diet

Contributor Marc O’Meara, RD, LDN, CDE
7 minute read
Controlling blood sugar with diet

Diabetes is a disease that causes high levels of glucose (sugar) in your blood. Over time, high blood sugar can damage tiny blood vessels throughout your body. Controlling your blood sugar can help you prevent or delay long-term damage to your heart, eyes, feet, and kidneys.

Many people find changing eating habits to control blood sugar challenging, says Marc O’Meara, RD, LDN, CDE, senior nutritionist at Mass General Brigham. O’Meara works with patients at Brigham and Women’s Hospital, Brigham outpatient settings, and virtually.

“Our society is not really set up to support people trying to control their blood sugar,” explains O’Meara. “Many of the foods we buy are processed and contain a lot of sugar. Carbs are quick and easy and delicious. It can be pretty hard to break these habits and learn how to manage blood sugar.”

O’Meara helps people with diabetes make small but meaningful changes to their diet to balance blood sugar. He says the key is balance — mixing sugars and carbohydrates with protein, fiber, and healthy fats.

“There are practical ways and small changes to make a difference in the long run,” he adds. 

Use protein to lower blood sugar.

Controlling your blood sugar often involves limiting foods such as fruits, candy, and sweetened drinks that contain obvious sugar. But starches such as bread and pasta also contain a lot of sugar in the form of carbohydrates — long, complex chains of sugars.

“Starch may not taste sweet. But when it’s digested, that carbohydrate chain is broken up into a big pile of sugars,” O’Meara says. “And those sugars, once they are in the gut, rush into the bloodstream.”

Eating protein — from meat and fish, tofu, nuts, eggs, and cheese — with carbs can slow that flow of glucose and help stabilize blood sugar.

“Proteins hold back the sugars, slow them down, and then release them into the bloodstream slowly so that your blood sugar stays in a more normal range,” O’Meara says.

He advises aiming to eat equal-sized portions of protein and carbohydrates to ensure you’re getting enough protein to counteract the carbs. 

Balance blood sugar with these foods.

Certain types of foods are especially effective at controlling blood glucose. O’Meara recommends a diet rich in whole grains, vegetables, nuts, seeds, and healthy fats.

Whole grains and fiber

Whole grains such as whole wheat bread and pasta, brown rice, oats, and quinoa are an excellent source of fiber. Fiber acts like an outer shell covering these carbs. That shell has to be broken down, so there’s a slight delay in the flow of sugars into the bloodstream. Whole grains not only help control diabetes but can help lower cholesterol and prevent other chronic diseases, O’Meara adds. However, whole grains are still carbs, so they can make blood sugar spike when you eat too many.

Leafy greens and non-starchy vegetables

Leafy greens such as romaine, kale, and spinach, along with non-starchy vegetables (for example, peppers, tomatoes, and onions) are high in fiber, low in calories, and nutrient-rich. O’Meara suggests filling at least half your plate with vegetables and eating them early in the meal. You’ll feel full faster and not overeat carbs.

Nuts, nut butters, and seeds

All nuts are high in protein and healthy fats. Healthy fats slow your digestive system and the rush of sugar from your gut to the bloodstream. O’Meara recommends no-salt or low-salt nuts of any kind, as well as nut butters processed without added sugar. Seeds — chia, flax, pumpkin, sunflower, and sesame — are another great option, especially for people with nut allergies.


All fruits contain natural sugar, but berries have the lowest amount. They also contain more fiber than most other fruits, plus lots of healthy nutrients. But eat them with protein such as Greek yogurt, nuts, or cheese to help counteract the glucose, O’Meara advises. 

Our society is not really set up to support people trying to control their blood sugar. Many of the foods we buy are processed and contain a lot of sugar. Carbs are quick and easy and delicious. It can be pretty hard to break these habits and learn how to manage blood sugar.

Marc O’Meara, RD, LDN, CDE

Senior Nutritionist

Mass General Brigham

Calculate a balance between net carbs and protein.

Food labels list calories, fat, cholesterol, sugars, carbs, and other items. But for people with diabetes, those numbers don’t tell the whole story. High-starch foods affect blood glucose just as much as sugary foods do. But food labels don’t tell you how much starch is in a food.

“Starch turns into sugar about 15 minutes after you eat it, and it can really rush into the bloodstream quickly,” O’Meara says.

He recommends the following formula: Take the total carbohydrates and subtract the fiber. That gives you the net carbs. Subtract the sugar from the net carbs. Then you know your total starches.

“Let’s look at Cheerios as an example. They have 29 grams of total carbohydrates and 6 grams of fiber per serving. So the net carbs are 23, and this represents sugar plus starch. But there are only 2 grams of sugar listed on the label. So this means there are 21 grams of starch in one and a half cups of Cheerios,” he says. “People eat Cheerios because they are low sugar, but blood sugars become elevated from all the starches turning into sugar soon after eating.”

People with diabetes should limit serving sizes of starchy foods. Eating high-starch foods with similar amounts of protein balances the resulting sugars.

“So if you are serving yourself rice and chicken, keep the rice portion the same size or smaller than the chicken portion. This will balance the net carbs and protein grams,” O’Meara explains. “If protein grams are within 10 grams of net carb grams, consider it a balanced food that will control the sugars as they enter the bloodstream.”

Lifestyle habits for balancing blood sugar

A balanced diet goes a long way toward controlling blood sugar. But healthy lifestyle choices also have a positive effect, O’Meara stresses. Your blood sugar balance also may improve when you:

  • Exercise: Exercise helps in two ways. Consistent activity boosts your metabolism so you are better able to burn off sugars. And if you have a high-carb meal, taking a walk immediately or participating in another activity can burn off excess sugars in the bloodstream.
  • Stay hydrated: Staying well hydrated helps stabilize blood sugar. In addition, hot liquids tend to make you feel fuller and more satisfied, so they may reduce snacking that raises blood sugar.
  • Get adequate sleep: When you get enough sleep, you have more energy and can be more active. Plus, studies indicate that poor sleep is linked to higher sugar levels.


Marc O’Meara, RD, LDN, CDE


Marc O’Meara, RD, LDN, CDE
Senior Nutritionist