Prediabetes is a metabolic warning sign—a state where blood sugar levels climb higher than normal but haven't yet crossed the threshold into type 2 diabetes. The condition affects roughly one in three American adults, yet many don't realize they have it. While genetics and activity levels play a role, diet is the most powerful lever you can pull. And according to dietitians, three specific categories of food are particularly likely to nudge your blood sugar in the wrong direction.
Here's what the experts want you to know about the everyday foods that may be raising your prediabetes risk—and how to think about them differently without feeling deprived.
1. Sugary drinks: The fastest route to a glucose spike
If there's one item dietitians agree on, it's that liquid sugar is uniquely problematic for blood sugar control. Sodas, sweetened iced teas, fruit punches, and even seemingly "healthy" bottled smoothies deliver a rapid flood of glucose with virtually no fiber, protein, or fat to slow absorption.
"A 12-ounce soda contains about 40 grams of added sugar, and that hits your bloodstream within minutes," says registered dietitian Marissa Meshulam. "For someone with prediabetes, that can push blood sugar to levels that accelerate progression toward diabetes."
The problem isn't just the sugar itself—it's how easily we consume it. A large soda at a convenience store can contain 60 to 80 grams of sugar, rivaling the total daily limit recommended by the American Heart Association in a single drink.
Tip: Swap one daily sugary drink for sparkling water with a splash of citrus or berries. Even small reductions can improve fasting glucose over time.
2. Refined carbohydrates: White bread, white rice, and instant cereals
Not all carbs are created equal, and the ones that have been stripped of their fiber are especially troublesome for prediabetes. White bread, white rice, pasta made from refined flour, and instant oatmeal products are digested quickly, converting to glucose almost as fast as table sugar.
"Refined carbohydrates have a high glycemic index, which means they cause a sharp rise in blood sugar," explains registered dietitian nutritionist Melissa Groves Azzaro. "When you have prediabetes, your body's insulin response is already blunted. Eating these foods regularly keeps your system overworked."
Dietitians emphasize that it's not about eliminating carbs—it's about upgrading them. Swapping white rice for quinoa, barley, or brown rice, and choosing 100 percent whole-grain bread or sourdough (which has a lower glycemic impact due to its fermentation process) can make a substantial difference.
What about whole grains?
Whole grains such as oats, farro, and bulgur contain the bran and germ, which provide fiber that slows sugar absorption. These are not the culprits. The issue arises when refined grains are a staple at multiple meals—think white toast for breakfast, a sandwich on white bread for lunch, and pasta for dinner.
3. Ultra-processed snacks and packaged sweets
Cookies, crackers, granola bars (many of which are closer to candy bars), chips, and sweetened breakfast cereals fall into a category that dietitians describe as "metabolic disruptors." These foods are engineered for taste and shelf stability, not for blood sugar stability.
"Ultra-processed foods combine refined flour, added sugars, and unhealthy fats in a way that makes them highly palatable but very low in nutrients that protect against blood sugar spikes," says registered dietitian Vandana Sheth. "They also tend to displace whole foods that provide fiber, protein, and healthy fats—things that actually help manage prediabetes."
Research published in the journal Diabetes Care found that each 10 percent increase in ultra-processed food consumption was associated with a 15 percent higher risk of developing type 2 diabetes. For someone already in the prediabetic range, the effect is likely even more pronounced.
This doesn't mean you can never have a cookie. It means that if your daily snacking routine includes packaged baked goods or sugary cereals, it's worth examining how often they appear and what you could swap in their place.
What to eat instead: A dietitian's short list
Foods that actively support better blood sugar control are the ones your grandmother would recognize: vegetables, legumes, nuts, seeds, whole fruits, lean proteins, and whole grains. Dietitians recommend building meals around non-starchy vegetables, adding a source of protein (eggs, tofu, chicken, fish, or beans), and including a small amount of healthy fat from sources like avocado, olive oil, or nuts.
"The goal isn't perfection—it's pattern shift," notes Meshulam. "Even one or two changes per week can lower your average blood sugar over the course of a month."
When to get proactive
If you have risk factors such as a family history of type 2 diabetes, a body mass index over 25, or a history of gestational diabetes, it's wise to ask your doctor for a fasting plasma glucose test or an HbA1c test, which reflects your average blood sugar over the past three months. Many cases of prediabetes are reversible with dietary changes, increased physical activity, and modest weight loss—but only if you know about it.
Focusing on these three food categories—sugary drinks, refined grains, and ultra-processed snacks—is a practical, evidence-based way to lower your risk without overhauling your entire diet overnight. Small, consistent swaps add up to real metabolic change.
