Research reviewed by Gram found that among 221 physically active young adults, those eating the most insulin-triggering diets had METS-IR scores 1.12 points lower than those eating the least. Overall diet insulin index showed few links to blood sugar markers. Because the study was cross-sectional, it shows association, not cause.
According to research reviewed by Gram, a 2026 study of 221 physically active adults aged 18 to 35 in Tabriz, Iran, found that people eating the most insulin-triggering diets had a lower score on METS-IR, a marker linked to insulin resistance. Their scores were 1.12 points lower than those of people eating the least insulin-triggering diets. The overall dietary insulin index, which measures how strongly foods trigger insulin, showed little connection to most blood sugar markers. Because the study looked at participants at a single point in time, it cannot prove that diet caused these differences. The researchers also suggested that regular exercise may soften the metabolic effects of insulin-heavy eating, though they did not directly test this idea. Larger, longer studies are needed before firm conclusions can be drawn.
Key Statistics
A 2026 cross-sectional study of 221 physically active adults aged 18 to 35 in Iran found that those with the highest dietary insulin load had METS-IR scores 1.12 points lower than those with the lowest load (p = 0.04).
In the same 2026 study, lower C-peptide levels appeared only in the middle dietary insulin load group, while the overall trend across all three groups was not statistically significant (p = 0.09).
The Quick Take
- What they studied: Researchers wanted to know whether the insulin-triggering potential of a person’s diet is linked to blood sugar, insulin, and related health markers in physically active young adults.
- Who participated: The study included 221 apparently healthy adults aged 18 to 35 who were recruited from sports clubs in Tabriz, Iran. All of them were physically active, and none were known to have a health condition.
- Key finding: People in the highest insulin-load group had a METS-IR score 1.12 points lower than people in the lowest group (p = 0.04). The overall insulin index of diet showed few meaningful links to most blood sugar markers.
- What it means for you: This study suggests that the insulin impact of your overall diet may matter more than the insulin index of individual foods. Because the study only shows an association, it should not be used to change eating habits on its own. Talk with a doctor or dietitian before making major diet changes.
The Research Details
This was a cross-sectional study, which means researchers took a snapshot of participants at one point in time instead of following them over months or years. Each participant completed a food frequency questionnaire, a form that asks how often they eat different foods. Researchers used these answers to calculate two scores: the dietary insulin index (DII), which rates how strongly foods trigger insulin, and the dietary insulin load (DIL), which also accounts for how much of each food people typically eat.
Participants were then divided into three groups, called tertiles, based on their DII and DIL scores. The team measured body measurements such as weight and height, along with blood samples that tested fasting blood sugar, insulin, C-peptide, and other markers. They also calculated two newer index scores, TyG-BMI and METS-IR, which combine blood and body measurements to estimate insulin resistance.
To make fair comparisons, the researchers used statistical models that adjusted for other factors that could affect the results, such as age, sex, and body size. This approach helps separate the effect of diet from other influences, although it cannot remove every possible factor.
A snapshot study like this is a useful first step for spotting patterns between diet and metabolism. It can show which markers are worth studying more closely in larger groups. Because the study measured diet and blood markers at the same time, however, it cannot tell whether the diet caused the changes or whether the changes influenced what people chose to eat.
The study used a validated food questionnaire and standard blood tests, which supports the reliability of the measurements. It adjusted for common influences on blood sugar and included a reasonably sized group for a study of this type. However, the sample came from one city and one type of population, which limits how widely the results can be applied. Readers should treat the findings as early evidence rather than settled fact.
What the Results Show
The clearest result was that people in the highest dietary insulin load group had a lower METS-IR score than people in the lowest group. The difference was about 1.12 points, and the result reached statistical significance (p = 0.04). METS-IR is a tool that estimates insulin resistance, which is the body’s reduced response to its own insulin. In this study, a higher diet insulin load did not appear to raise this marker, which was unexpected and deserves further testing.
The researchers also looked at C-peptide, a substance the body releases when it makes insulin. Lower C-peptide levels were seen in the middle insulin load group, with a statistically significant result (p = 0.04). However, the highest group did not show a significant difference, and the overall pattern across all three groups was not statistically significant (p = 0.09). This means the C-peptide finding should be viewed with caution.
In contrast, the dietary insulin index (DII) was not clearly linked to most blood sugar markers, including fasting glucose and insulin. It showed only a borderline trend with QUICKI, a measure of insulin sensitivity, which is not strong enough to draw conclusions. Taken together, the researchers concluded that the total insulin load of a diet may relate to blood sugar patterns more closely than the insulin index alone.
Beyond the main comparisons, the study found that most other markers, including fasting blood sugar, insulin levels, HOMA-IR, and TyG-BMI, did not show meaningful differences across diet groups. This lack of effect is also informative. It suggests that, in this group of active young adults, diet insulin scores may not strongly change everyday blood sugar readings. The researchers suggested that regular physical activity might explain part of this, since all participants were active, but the study did not compare active and inactive people directly.
Research on insulin-triggering diets has often focused on the general population, where links to insulin resistance and type 2 diabetes are more commonly reported. This study adds to that work by looking at physically active young adults, a group that has been studied less. Its results are partly consistent with the idea that diet insulin load matters for metabolism, but they also suggest that the connection may be weaker in people who exercise regularly. More research is needed to confirm whether this pattern holds across different populations.
The most important limitation is the study design. Because it looked at diet and health markers at one point in time, it can show that two things are associated but cannot prove that one caused the other. Diet data also came from a questionnaire, which depends on people remembering what they ate and estimating portion sizes. Errors in these memories can blur real differences.
The group was small, drawn from sports clubs in one city, and included only young, active adults. Results may not apply to older adults, people with health conditions, or those who do not exercise. Some findings were borderline or not statistically significant, so they should not be treated as firm evidence. The study also did not directly test whether exercise changes the effect of diet, so the idea that activity may soften diet-related effects remains a suggestion rather than a proven fact.
The Bottom Line
Current evidence from this study is preliminary, so confidence in any specific recommendation is low. The findings suggest that the total insulin impact of a diet, rather than the insulin index of single foods, may be worth watching. Eating a balanced diet with plenty of vegetables, whole grains, lean proteins, and healthy fats is supported by a broad body of research, although this study does not directly test those foods. Anyone with concerns about blood sugar should discuss them with a healthcare provider.
Physically active young adults who want to understand how their diet may relate to blood sugar may find this study interesting. Athletes, fitness enthusiasts, and people working with a dietitian may also benefit from knowing that diet and exercise appear to interact. People with diabetes, prediabetes, or a family history of metabolic disease should speak with a doctor before making changes based on this research. Children, older adults, and people with health conditions were not part of this study, so its findings may not apply to them.
Because this is a single snapshot study, it does not offer a timeline for benefits. Changes in blood sugar markers such as fasting glucose or insulin usually take several weeks to months of consistent diet changes to show up on lab tests. Any changes in how your body handles insulin would need to be confirmed through repeated testing over time, ideally with guidance from a healthcare provider.
Frequently Asked Questions
Does eating foods that raise insulin affect blood sugar in active young adults?
A 2026 study of 221 physically active adults aged 18 to 35 found that a higher dietary insulin load was linked to lower METS-IR scores, but the study could not prove cause. The overall dietary insulin index showed few links to blood sugar markers such as fasting glucose and insulin.
What is dietary insulin load?
Dietary insulin load estimates how strongly a person’s typical diet triggers insulin release, taking into account both how strongly each food raises insulin and how much of it is eaten. The 2026 study calculated it from a food questionnaire and compared three groups of participants.
Can regular exercise offset the blood sugar effects of insulin-heavy foods?
Researchers suggested that regular physical activity may soften adverse metabolic responses to insulin-heavy diets. However, the study included only active adults and did not directly compare them with inactive people, so larger trials are needed before exercise can be relied on as a buffer.
What is C-peptide and why does it matter?
C-peptide is a substance released when the pancreas makes insulin, so its level reflects how much insulin the body produces. In a 2026 study of 221 young adults, C-peptide was lower only in the middle insulin load group, and the overall trend was not statistically significant.
Want to Apply This Research?
- Log your meals for two weeks and note how many servings you eat from high-insulin foods such as white bread, sugary drinks, potatoes, and sweets each day. Track your weekly servings of vegetables, legumes, and whole grains as well. Review the weekly totals to see whether your overall pattern is trending higher or lower in insulin-triggering foods.
- Use the app to set one small, measurable goal, such as swapping one daily refined-grain serving for a whole-grain option or adding one extra vegetable serving per meal. Pair this goal with your regular exercise routine and log both so you can see how they fit together over time. Share the results with a healthcare provider if you have blood sugar concerns.
- Review your food log and exercise log each month and look for patterns in how your diet and activity change over time. If you have access to blood tests through a doctor, record fasting glucose and insulin results alongside your diet data so you can compare trends. Update your goals every three months, and seek professional guidance if you notice unexplained changes in energy, weight, or blood sugar.
This article summarizes a single cross-sectional study of 221 young adults in one city and is provided for general information only. It is not medical advice and does not replace consultation with a doctor, registered dietitian, or other qualified healthcare provider. If you have diabetes, prediabetes, a family history of metabolic disease, or take medication, speak with a healthcare professional before changing your diet or exercise routine.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.