Does Eating too Much Sugar Cause Diabetes?
There are a lot of factors that play a role in type 2 diabetes, and sugar is just one of them.
Chances are you have a family member, close friend, or colleague who has diabetes. (That person might even be you.) This chronic and serious health condition affects about one in ten people, and that number rises with age—half of all adults in the United States have diabetes or prediabetes, reports the American Diabetes Association.
We are mostly talking about type 2 diabetes here because it’s, by far, the most common form of the disease, accounting for about 90 to 95 percent of all cases. (Type 1 diabetes and gestational diabetes are the other main types.)
What all types of diabetes have in common is that people have blood glucose—blood sugar—that is too high. Does that mean that eating sugar causes diabetes? The answer for type 1 diabetes is always no—this comparatively rare type of diabetes is an autoimmune condition that is unrelated to lifestyle factors like food intake or exercise.
For type 2 diabetes it’s a bit more complicated. If you already have a genetic risk and you have a consistently unhealthy eating pattern, excess weight, and a sedentary lifestyle, you are at risk of developing type 2 diabetes earlier—say in your 20s, 30s, or 40s—rather than later in life, in your 50s, 60s, or 70s. So how does sugar fit in?
To understand the role that eating sugar plays in type 2 diabetes, it helps to take a quick look at how sugar in the blood, or blood glucose, can end up too high.
Blood sugar is most heavily influenced by carbohydrates, which are found in everything from fruits and potatoes to bread, sweets, and soda. During digestion, carbs are broken down into glucose and released into your bloodstream. That’s a good thing: glucose is our body’s main source of energy. Your body cells must have the energy to function, but that same glucose can be toxic at high levels in your blood.
In fact, it’s so dangerous that uncontrolled blood sugar can harm vision, cause nerve damage, and lead to heart disease, stroke, kidney failure, and all kinds of problems. That’s why your body has an exquisitely calibrated system for keeping glucose at safe levels.
To function as an energy-maker, glucose needs to leave the blood and get inside your body’s cells, says Diana Licalzi, a Boston-based registered dietitian nutritionist. This is where insulin comes in. Produced by the pancreas, insulin acts like a key, unlocking the cell to allow glucose to get inside.
Licalzi explains the process: “You eat an apple, the apple turns into glucose, the pancreas releases insulin, the insulin opens the doors to the cell, the glucose enters and energy is produced for use right away with the leftovers stored for use later.”
With type 2 diabetes, the cell’s ability to respond to insulin is impaired and sugar lingers in the bloodstream instead of being efficiently dispatched to the cells. (This is known as insulin resistance.)
Insulin resistance can be caused by many things, including excess weight, unhealthy eating patterns, a lack of exercise, and certain medications.
Being overweight increases your risk
There’s no one cause of type 2 diabetes or prediabetes, according to the U.S. National Institute of Diabetes and Digestive and Kidney Diseases. Genes and family history can play a role, and there isn’t much you can do about that. But when it comes to the factors you can control, maintaining a healthy weight is on the top of the list in preventing the disease, delaying its onset, or slowing its progression.
“Carrying excess weight, especially around the abdomen, increases your risk of type 2 diabetes, as well as of other diseases like high blood pressure, heart disease, and even stroke,” says Licalzi.
A 2015 study published in the International Journal of Preventative Medicine suggests waist measurement can be as equally important as body mass index (BMI)—a ratio of weight and height—when it comes to predicting a person’s disease risk, especially in type 2 diabetes.
Men should aim for a waist circumference of 40 inches or less and women should aim for 35 inches or less, according to the American Heart Association. Those who are lower weight, but have a large waist circumference—meaning, more belly fat—are also at a higher risk of developing type 2 diabetes.
Healthy eating is about more than just sugar
Sugar is not the only culprit contributing to the rise of type 2 diabetes in the U.S. “The overall quality of the standard American diet is responsible for the development of diabetes type 2 or prediabetes,” says UCLA dietitian Dana Hunnes. “The typical diet is high in processed carbohydrates, fat, animal proteins, and salt, and low in fiber, water, fruits, and vegetables.” That high caloric tally promotes weight gain. Meanwhile, all those simple carbs—in things like French fries, chips, sugar-sweetened beverages, pasta, and bread made from white flour— lead to a fast rise in blood sugar. When that happens, your body struggles to churn out more and more insulin—which fails to lower blood glucose because the cells are ignoring it.
Over time, those spikes tend to wear out your insulin-producing cells altogether and the body stops making insulin. If you have prediabetes or type 2 diabetes, that means that each time you eat, blood sugar just keeps climbing higher and higher unless you control it with diet, exercise, and medication.
Sugar gets an F in nutrition
A sugary treat once in a while is not a problem. But too much over too long a period of time increases the risk of weight gain and puts stress on your insulin-producing cells. “Calories from sugar are what we call empty calories,” says Licalzi. “They have little or no nutritional value.” And since sugar calories do little to satisfy hunger, it’s easy to devour large amounts and start putting on extra pounds.
The average American consumes 17 teaspoons of sugar a day. That’s more than three times the 6 teaspoons, or 25 grams, that’s recommended for women and nearly twice the 9 teaspoons (36 grams) recommended for men by the American Heart Association. Consider that a single 12-ounce serving of soda has about 40 grams of added sugar, and you get a sense of how easy it is to consume health-endangering levels of sugar.
Looked at another way, Jo Mandelson, RDN, a nutritionist with the American Diabetes Association, points out that the Dietary Guidelines for Americans, including those with prediabetes and type 2 diabetes, suggest limiting added sugar in food and beverages to 10 percent of calories per day. That works out to about 160 to 300 calories, depending on sex, age, height, and activity level.
Try to cut back on hidden sugar
We all know that chocolate-covered donuts, three scoops of ice cream drowned in caramel sauce, and a thick slab of strawberry shortcake are sugar bombs. But sugar can also be hidden, in salad dressing and ketchup, tomato sauce, cereal or granola, flavored yogurt, and bread. Unlike sugars that naturally occur in foods like fruit, these “added sugars” are put in foods during production.
Dana Hunnes, a senior dietitian at Ronald Reagan UCLA Medical Center in Los Angeles, recommends becoming a savvy sugar sleuth. “I always suggest,” she says, “that you scan labels for ingredients such as monosaccharides, disaccharides, sucrose, high fructose corn syrup, corn syrup, agave nectar, molasses, cane juice, cane sugar, date sugar, and evaporated cane juice. Any of these could be added sugars.” The Food and Drug Administration’s new food label requirements make it a cinch to find how much sugar has been added during processing: Just look for the line that says “added sugars.”
Fiber helps fight type 2 diabetes
From brown rice to black beans, whole-grain cereal, fruits, vegetables, and popcorn, fiber is a powerful ally in the fight against type 2 diabetes. “Fiber-rich foods are digested more slowly,” says Licalzi, “so your blood sugar doesn’t spike and you stay fuller longer.” A 2019 review in The Lancet that included nearly 250 studies found that people who ate the highest amount of fiber had a 16% to 24% lower risk of dying from type 2 diabetes, heart disease, stroke, and colon cancer, compared with people who ate very little fiber.
However, Americans are not getting enough fiber in their diet. The U.S. Department of Agriculture recommends 25 grams a day for women and 38 grams a day for men, up to the age of 50. After 50, women should aim for 21 daily grams and men, 30 grams. The average American only eats an average of 10 to 15 grams of fiber a day.
Eating more plants can help
Choosing foods that help control blood sugar and prevent type 2 diabetes doesn’t have to be confusing. Simply ask yourself this question when choosing ingredients: Did it grow in the ground or on a tree, vine, or bush? If the answer is yes, you’re on the right track.
A 2019 study published in JAMA Internal Medicine found that people who followed a predominantly plant-based diet with a mix of fruits, vegetables, whole grains, nuts, and legumes had a lower risk of developing type 2 diabetes, and those that eliminated less healthy foods such as white flour and sugar saw the greatest benefit. Hunnes says that, for some people, moving to a “primarily whole-foods, plant-based diet” might be as helpful as drugs in reducing the risk of prediabetes or type 2 diabetes.
Another powerful ally: Exercise
Don’t let perfection be the enemy of better when it comes to taking steps to lower your type 2 diabetes risk. Small changes can make a big difference when it comes to lowering your risk.
Just ask Zaira Ortega, MD, a family medicine physician in East Los Angeles, a community where type 2 diabetes is a pressing health concern. “When patients have a family history of diabetes or prediabetes,” she says, “we tell them that they have the power to change the course of their future health.”
Among her simple tips: Switch from drinking juice to eating whole fruit. Instead of eating five tortillas for dinner, cut back to two. Swap white rice for fiber-rich quinoa. And while, Dr. Ortega says, “80 percent of weight loss takes place in the kitchen,” exercise plays an important role, too. She tells her patients to aim for 30 minutes of moderate to vigorous exercise, five days a week.
In fact, exercise is as powerful as some diabetes medications when it comes to lowering blood sugar. It boosts insulin sensitivity and encourages body cells to absorb blood glucose. While it’s not always easy to find the time or motivation to exercise, you might want to invite a friend to join you for a brisk walk to help maintain your blood sugar levels and body weight. Both the American College of Sports Medicine and the American Diabetes Association recommend going on a 30-minute walk at least five days per week.
So does sugar cause type 2 diabetes? No, but it doesn’t help. Your best bet is to limit added sugar, increase your fiber, fuel your body with healthy carbohydrates, and get some exercise to keep your blood sugar in the safe zone.
For more diabetes insight, see the best remedies for diabetes and the worst eating habits for diabetes.
- Centers for Disease Control and Prevention: "Type 2 Diabetes"
- National Institute of Diabetes and Digestive and Kidney Diseases: "What is type 2 diabetes?"
- Diana Licalzi, MS, RDN, a Boston-based registered dietitian nutritionist
- NIDDK: “Symptoms & Causes of Diabetes”
- International Journal of Preventative Medicine: “Is waist circumference a better predictor of diabetes than body mass index or waist-to-height ratio in Iranian adults?”
- CDC: “Defining Adult Overweight and Obesity”
- American Heart Association: “Body Mass Index (BMI) In Adults”
- University of California San Francisco: “How Much Is Too Much?”
- American Heart Association: “Added Sugars”
- Jo Mandelson, MS, RDN, registered dietitian nutritionist with the American Diabetes Association
- Dana Hunnes, a senior dietitian at Ronald Reagan UCLA Medical Center in Los Angeles
- Food and Drug Administration: "Changes to the Nutrition Facts Label"
- Lancet: “Carbohydrate quality and human health: a series of systematic reviews and meta-analyses”
- U.S. Department of Agriculture: “Basic Nutrition”
- USDA: “Fiber intake of the U.S. population What We Eat in America, NHANES 2009-2010”
- JAMA Internal Medicine: “Association Between Plant-Based Dietary Patterns and Risk of Type 2 Diabetes: A Systematic Review and Meta-analysis”
- Zaira Ortega, MD, is a family medicine physician in East Los Angeles
- Diabetes Care: “Exercise and Type 2 Diabetes: The American College of Sports Medicine and the American Diabetes Association: joint position statement”