If you’ve been told your blood sugar is in the prediabetic range (an A1c between 5.7% and 6.4%), what you remove from your plate matters just as much as what you add to it. The foods that do the most damage share a common trait: they cause rapid, steep spikes in blood sugar that force your body to pump out extra insulin. Over time, that cycle wears down your body’s ability to use insulin effectively, pushing you closer to type 2 diabetes. Here’s what to cut back on or avoid entirely.
Refined Carbohydrates and White Starches
Refined grains are the single biggest category to watch. When whole grains are processed into white flour, the fiber and outer layers that slow digestion get stripped away. What’s left is essentially a fast-acting sugar delivery system. Foods with a glycemic index of 70 or higher, meaning they spike blood sugar almost as fast as pure glucose, include white bread, bagels, rice cakes, most crackers, croissants, cakes, doughnuts, and the majority of packaged breakfast cereals.
These foods are so common that they often make up the backbone of a typical meal: a bagel at breakfast, a sandwich on white bread at lunch, crackers as a snack. Swapping them for whole-grain or lower-glycemic alternatives (steel-cut oats, 100% whole wheat bread, quinoa) can meaningfully slow the rate at which sugar enters your bloodstream after eating.
Sugary Drinks and Fruit Juice
Sodas, sweet teas, energy drinks, and fruit juices are among the worst offenders for anyone with prediabetes. A single 12-ounce can of regular soda contains roughly 39 grams of sugar, and because it’s liquid, your body absorbs it almost immediately. There’s no fiber or fat to slow things down, so blood sugar spikes hard and fast.
Fruit juice deserves special attention because many people assume it’s healthy. Even 100% juice with no added sugar delivers a concentrated dose of fructose without the fiber you’d get from eating the whole fruit. An 8-ounce glass of orange juice has about the same sugar content as a glass of soda. Whole fruit is a better choice because the intact fiber slows absorption significantly.
Ultra-Processed Packaged Foods
Chips, frozen meals, instant noodles, packaged snack cakes, and fast food fall into the ultra-processed category. These foods tend to combine refined starches, added sugars, and unhealthy fats in ways that are particularly damaging. A study from the Keck School of Medicine at USC tracked 85 young adults over four years and found that a 10% increase in ultra-processed food consumption was associated with a 64% higher risk of developing prediabetes and a 56% higher risk of impaired glucose regulation. Participants who ate more of these foods also showed elevated insulin levels at follow-up, an early marker of insulin resistance.
The problem with ultra-processed foods goes beyond any single ingredient. They’re engineered to be easy to overeat, they digest quickly, and they often contain multiple forms of hidden sugar (more on that below). Replacing even a portion of your ultra-processed intake with whole foods, things like vegetables, nuts, eggs, and legumes, can shift the trajectory.
Foods With Hidden Sugar
Sugar hides in places you wouldn’t expect: flavored yogurt, granola bars, instant oatmeal packets, canned soup, pasta sauce, and even whole wheat bread. Manufacturers use dozens of different names for sugar on ingredient labels. The CDC flags several to look for: cane sugar, turbinado sugar, corn syrup, high-fructose corn syrup, rice syrup, molasses, caramel, agave, and honey. Any ingredient ending in “-ose” (glucose, fructose, maltose, dextrose, sucrose) is also a sugar.
A practical habit: check the “added sugars” line on the nutrition label rather than trying to decode every ingredient. If a product has more than 4 or 5 grams of added sugar per serving, consider whether there’s a lower-sugar version or a whole-food alternative.
Condiments and Sauces
Condiments are a sneaky source of sugar that can add up quickly, especially because serving sizes on the label are often much smaller than what people actually use. A single tablespoon of ketchup has about 4 grams of added sugar, but most people pour three to five tablespoons at a sitting. Barbecue sauce is worse, sometimes packing more than 12 grams of sugar per serving. Sweet chili sauce, teriyaki sauce, hoisin sauce, and French dressing are similarly high.
Better options include mustard, hot sauce, vinegar-based dressings, salsa, and herbs or spices. If you don’t want to give up ketchup or BBQ sauce entirely, look for “no sugar added” versions, which are now widely available.
Saturated Fat and Fried Foods
While the sugar connection to blood sugar is obvious, fat plays a less intuitive but important role. Diets high in saturated fat contribute to insulin resistance independently of weight gain. When excess fat accumulates in the liver, it triggers a chain of events that impairs insulin signaling, making your cells less responsive to insulin even when your body produces plenty of it. Common high-saturated-fat foods include fatty cuts of red meat, full-fat cheese, butter, cream, and anything deep-fried.
Trans fats, found in some margarines, packaged baked goods, and fried fast food, are even more harmful. While many countries have restricted artificial trans fats, they still show up in some products. Checking ingredient labels for “partially hydrogenated oil” is the most reliable way to spot them. Replacing some saturated fat with unsaturated sources like olive oil, avocado, nuts, and fatty fish improves insulin sensitivity over time.
Alcohol, Especially Beer and Mixed Drinks
Alcohol and blood sugar have a complicated relationship. Beer is high in carbohydrates, and sweetened cocktails (margaritas, daiquiris, piña coladas) can contain as much sugar as a dessert. A single frozen margarita may pack 30 or more grams of sugar. These drinks spike blood sugar in the short term.
On the flip side, alcohol can also cause blood sugar to drop too low hours later, particularly if you haven’t eaten. This unpredictable swing makes alcohol harder to manage with prediabetes than most people realize. If you do drink, dry wine and spirits without sugary mixers have the least impact on blood sugar. Keeping portions moderate, one drink per day for women and two for men, is the general guideline.
Putting It Into Practice
You don’t need to overhaul everything at once. The highest-impact changes for most people with prediabetes are cutting sugary drinks, replacing refined grains with whole grains, and reducing ultra-processed snack foods. Those three shifts alone address the biggest sources of rapid blood sugar spikes in a typical diet.
Reading nutrition labels becomes second nature quickly. Focus on three lines: total carbohydrates, added sugars, and fiber. A food that’s higher in fiber relative to its total carbs will have a gentler effect on blood sugar. And pairing carbohydrates with protein, fat, or fiber at every meal slows digestion and flattens the post-meal blood sugar curve, even when the carbs themselves aren’t perfect.