Dr. Ahmed Farhan
Most of us have heard some version of this warning: processed food is bad for your blood sugar. It sounds simple. Eat less packaged food, and your blood sugar gets better.
But a new study looked much closer at this idea, using real-time blood sugar data from people with type 2 diabetes. And it found something more complicated — and more useful — than a simple warning. The way you count “processed food” seems to change whether it predicts blood sugar trouble at all.
Why This Is Getting Attention Now
The study was published in the September 2026 issue of Diabetes Research and Clinical Practice, led by researchers at Yale University.
It’s part of a much bigger wave of science looking at “ultra-processed foods,” or UPFs — a term for foods that are made mostly from industrial ingredients rather than things you’d cook with at home.
You’ve probably eaten UPFs today without thinking about it. Packaged snack cakes, sodas, chicken nuggets, flavored yogurts, and most breakfast cereals count. So do many veggie burgers and protein bars. These foods are built to be cheap, last a long time on a shelf, and taste so good it’s hard to stop eating them.
Scientists already know that people who eat a lot of UPFs tend to have higher rates of obesity, type 2 diabetes, and heart disease over time.
That link has shown up in large studies for years. What’s been missing is a clear picture of what UPFs do to blood sugar in the moment — hour by hour, meal by meal — in people who already have type 2 diabetes. This new study set out to fill that gap.
What the Researchers Actually Did — and Found
The research team worked with 190 adults who have type 2 diabetes. Each person wore a continuous glucose monitor (CGM) — a small sensor that checks blood sugar every few minutes — for two weeks. At the same time, they reported everything they ate over two 24-hour periods.
Researchers then sorted every single food into categories using a well-known system called NOVA. NOVA sorts food into four groups, from “fresh or barely touched” (like a plain apple or a raw chicken breast) up to “ultra-processed” (like a fruit-flavored snack cake with a long ingredient list you can’t fully pronounce).
Here’s where it gets interesting. The team measured “how ultra-processed someone’s diet was” in two different ways:
- The whole-diet way: What share of a person’s total daily calories came from ultra-processed foods, added up across everything they ate.
- The food-level way: How ultra-processed the specific foods were, on average, across every single item they reported eating.
These sound almost the same. They aren’t.
When researchers checked the whole-diet measure against blood sugar results, they found no clear link.
But when they checked the food-level measure — looking closely at how ultra-processed each specific food item was — the picture changed completely. People whose individual foods scored higher on the ultra-processed scale were:
- Less likely to keep their blood sugar in a healthy range for at least 70% of the day
- More likely to spend at least a quarter of their day with blood sugar running too high
- More likely to have an estimated long-term blood sugar average of 7% or higher — a marker doctors use to judge how well diabetes is being controlled
In plain terms: it wasn’t simply “how much” of the day’s calories were ultra-processed that mattered here. It was how intensely processed the specific foods actually were.
What This Means for Diabetes and Metabolic Health
This is a small but meaningful shift in how to think about food and blood sugar. It suggests that not all “ultra-processed” is created equal, and that lumping every packaged food into one big pile — then just adding up the percentage of your day’s calories — might miss what actually matters.
Instead, the specific foods you choose, even within the “ultra-processed” category, may carry more weight than the running percentage on a nutrition app.
A cup of flavored yogurt with a short, simple ingredient list is not the same, metabolically, as a fistful of gummy candy — even if a tracking app might lump both into “processed.”
This lines up with what researchers already understand about how the body handles different foods. Ultra-processed foods are often stripped of fiber, broken down into easy-to-absorb pieces, and packed with quick sugars or refined starches.
That combination can make blood sugar rise faster and higher than a less-processed version of a similar food.
The more of your plate that looks like this, the more work your body has to do to bring blood sugar back down — and for someone with type 2 diabetes, that job is already harder than it should be.
What We Know
- Continuous glucose monitors give a much more detailed picture of blood sugar than an occasional finger-stick or a lab test every few months.
- A large and consistent body of research links high UPF intake, over the long run, to higher rates of obesity, type 2 diabetes, and heart disease.
- In this new study, the specific foods people ate — not just the overall share of the day’s calories that were ultra-processed — predicted worse real-time blood sugar control.
- Time in range (the share of the day spent in a healthy blood sugar zone) and a related measure called the Glucose Management Indicator are both used by doctors and diabetes educators to understand day-to-day control, alongside the traditional A1C blood test.
What We Don’t Know
- This study shows a link, not a cause. It cannot prove that eating more ultra-processed food directly caused worse blood sugar readings in these participants.
- The study included 190 people over a two-week window. It’s a solid sample for this kind of detailed measurement, but it’s not the same as tracking millions of people for years.
- Researchers don’t yet know exactly which ingredients or processing methods are doing the most damage. Is it the lack of fiber? The type of starch? Specific additives? That’s still being worked out.
- It’s not yet clear whether swapping specific ultra-processed foods for less-processed versions would actually improve a person’s blood sugar over time. That would need to be tested directly.
Common Misconceptions
“All processed food is equally bad.” This study actually pushes back on that idea. It suggests some ultra-processed foods may matter more for blood sugar than others, even though NOVA groups them together.
“If I eat under a certain percentage of processed food, I’m fine.” Counting your overall percentage of daily calories from processed food, by itself, wasn’t linked to worse blood sugar in this study. What specific foods make up your plate may matter more than a single running number.
“Processed automatically means high in sugar.” Not always. Some ultra-processed foods are high in sugar; others are high in refined starch, unusual fats, or additives that change texture and shelf life without necessarily being sugary at all.
“This means I should never eat packaged food again.” The researchers aren’t calling for that. They’re calling for smarter identification of which processed foods deserve the most attention — not a blanket ban on anything in a wrapper.
Who Should Be Particularly Concerned
This research is most relevant to:
- People who already have type 2 diabetes and are working on day-to-day blood sugar control, especially anyone using a CGM
- People who eat a lot of packaged snacks, sweetened drinks, or ready-made meals and want a more precise way to think about which ones to cut back on first
- People with prediabetes or a family history of type 2 diabetes who are trying to build better habits early
- Caregivers or family members who help plan meals for someone managing diabetes
This is general health information, not a diagnosis or a personal treatment plan. Anyone managing diabetes should keep working with their own doctor or diabetes care team on specific goals.
Practical, Evidence-Based Recommendations
- Look past the “processed or not” checkbox. Instead of asking only “is this processed?”, look at the actual ingredient list. Foods with a short list of recognizable ingredients tend to behave differently in the body than foods with a long list of additives, refined starches, and added sugars.
- Pay attention to fiber. Whole grains, beans, vegetables, and fruit with the skin on tend to slow down how fast sugar enters the bloodstream. Many ultra-processed foods strip this fiber out.
- Notice patterns, not just percentages. If you use a CGM or track your meals, look at which specific foods line up with blood sugar spikes on your own data, rather than only tracking one overall “percent processed” number.
- Swap don’t just subtract. Rather than only cutting foods out, try trading a highly processed version of something for a less-processed version of the same craving — like plain yogurt with fruit instead of a flavored yogurt cup with added syrup.
- Bring your CGM data to your care team. If you already use a CGM, patterns around specific foods are exactly the kind of detail a doctor or dietitian can help you act on.
- Don’t chase a single number. Time in range, GMI, and A1C are all useful, but none of them tell the whole story on their own. Your care team can help you understand how they fit together for your specific situation.
Frequently Asked Questions
Does eating processed food always spike blood sugar?
Not always, and not equally. This study found that the overall share of daily calories from ultra-processed food wasn’t linked to worse blood sugar control — but how processed the specific foods eaten were, on average, was linked to it. Different processed foods appear to affect blood sugar differently.
What exactly counts as an “ultra-processed” food?
Under the NOVA classification system, ultra-processed foods are typically made mostly from industrial ingredients and often include additives you wouldn’t normally find in a home kitchen, such as certain preservatives, emulsifiers, flavorings, or sweeteners. Common examples include packaged snack cakes, sodas, instant noodles, and many breakfast cereals.
What is “time in range” and why does it matter?
Time in range (TIR) is the percentage of the day someone’s blood sugar stays within a healthy target zone, usually 70 to 180 mg/dL. Diabetes organizations generally suggest aiming for a TIR above 70% for most adults with diabetes, though individual targets can vary and should be set with a doctor.
Can I still eat some processed foods if I have type 2 diabetes?
This research doesn’t suggest all processed food needs to be eliminated. It suggests being more selective about which ultra-processed foods you eat often, based on ingredients and how your own blood sugar responds, rather than treating “processed” as one single category.
Is this study proof that processed food causes blood sugar problems?
No. This was an observational study, meaning it found a link between eating patterns and blood sugar readings — it didn’t test cause and effect by having people change their diets and then measuring what happened.
What is a Glucose Management Indicator (GMI)?
GMI is a number, similar to the A1C blood test, that estimates a person’s average blood sugar over time based on CGM readings. It’s a helpful additional data point for people using CGMs, alongside time in range and lab-measured A1C.
Conclusion
The old advice to “eat less processed food” isn’t wrong, but this new research suggests it’s a little too simple.
For people managing type 2 diabetes, the specific foods on the plate — how they’re made, not just how many of the day’s calories they add up to — may matter more than a single running percentage.
As CGMs become more common, expect more research like this: less about broad food categories, and more about which specific choices move the needle for your own body.
References
Nam S, Lee M, Juul F, Parekh N, Jeon S. Ultra-processed foods and continuous glucose monitoring metrics in adults with type 2 diabetes. Diabetes Research and Clinical Practice. 2026 Sep;239:113465.
Battelino T, Danne T, Bergenstal RM, et al. Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations From the International Consensus on Time in Range. Diabetes Care. American Diabetes Association / Endocrine Society consensus guidance on time-in-range targets.
Bergenstal RM, Beck RW, Close KL, et al. Glucose Management Indicator (GMI): A New Term for Estimating A1C From Continuous Glucose Monitoring. Diabetes Care. 2018;41(11):2275–2280.
Monteiro CA, Cannon G, Levy RB, et al. Ultra-Processed Foods: What They Are and How to Identify Them. Public Health Nutrition. 2019;22(5):936–941.
Li Y, Costello E, Rock S, et al. Ultra-Processed Food Intake Is Associated With Altered Glucose Homeostasis in Young Adults With a History of Overweight or Obesity: A Longitudinal Study. (Meta-AIR study, University of Southern California / Johns Hopkins Bloomberg School of Public Health.)
American Diabetes Association. Standards of Care in Diabetes—2026: Obesity and Weight Management for the Prevention and Treatment of Diabetes. Diabetes Care. 2026;49(Suppl 1):S166–S182.
