Researchers studied 34 people with diabetes using special devices that track blood sugar throughout the day. They found that people whose carbohydrate intake (foods like bread, rice, and pasta) varied a lot from day to day had higher average blood sugar levels and worse control. The study suggests that eating a more consistent amount of carbohydrates each day, rather than eating very different amounts on different days, might help people with diabetes keep their blood sugar more stable. This discovery could help doctors give better personalized advice about eating patterns.

The Quick Take

  • What they studied: Whether the way people’s carbohydrate eating patterns change from day to day affects how well their blood sugar stays controlled
  • Who participated: 34 adults with diabetes who wore continuous glucose monitors (devices that track blood sugar) for one week while keeping food records
  • Key finding: People whose carbohydrate intake varied the most from day to day had significantly higher average blood sugar levels. The variation in carbs was strongly linked to worse blood sugar control (correlation of 0.88, which is very strong)
  • What it means for you: If you have diabetes, eating roughly the same amount of carbohydrates each day—rather than eating very different amounts on different days—may help keep your blood sugar more stable. However, this is a small study, so talk with your doctor before making major diet changes

The Research Details

This was a prospective observational study, which means researchers followed people forward in time and observed what happened naturally without controlling their diet. Thirty-four people with diabetes wore continuous glucose monitors (CGM devices) for 7 days. These devices measure blood sugar levels throughout the day and night automatically. At the same time, participants recorded everything they ate. Researchers then used a statistical method called K-means clustering to group people into three categories based on their blood sugar patterns: those with well-controlled blood sugar, those with the most variable blood sugar, and those with the highest average blood sugar. Finally, they compared how much carbohydrates each group ate and how much that amount changed from day to day.

This research approach is important because it looks at real-world eating patterns and blood sugar responses together, rather than testing one specific diet in a controlled setting. By grouping people based on their actual glucose patterns, researchers can identify which eating habits are connected to better or worse control. This helps move toward personalized nutrition advice tailored to individual needs.

The study is relatively small (34 people), which means the findings may not apply to everyone with diabetes. It’s observational, meaning it shows associations but can’t prove that carbohydrate fluctuations directly cause higher blood sugar—other factors could be involved. The study was conducted over just one week, so longer-term patterns weren’t examined. However, the strong correlation between carbohydrate variation and blood sugar levels (0.88) suggests a meaningful relationship worth investigating further.

What the Results Show

Researchers divided participants into three groups based on their blood sugar patterns. The group with the highest average blood sugar (cluster 3) had much larger day-to-day changes in carbohydrate intake compared to the other two groups. Specifically, the standard deviation (a measure of how much things vary) of carbohydrate intake was 502 calories in cluster 3, compared to 260 calories in the well-controlled group and 250 calories in the high-variability group. This difference was statistically significant (P=0.024), meaning it’s unlikely to be due to chance. When researchers looked at the relationship between carbohydrate variation and average blood sugar levels, they found a very strong positive correlation (0.88), suggesting that as carbohydrate intake becomes more inconsistent, blood sugar tends to rise. Interestingly, the total amount of carbohydrates eaten each day didn’t differ significantly between groups—it was the day-to-day inconsistency that mattered.

The study found that basic clinical characteristics (like age, weight, and diabetes type) and total daily calorie intake were similar across all three groups. This suggests that the quality of glucose control wasn’t determined by how much people ate overall, but rather by the consistency of their carbohydrate intake. The coefficient of variation (a measure of blood sugar variability) was highest in cluster 2, but carbohydrate fluctuations didn’t differ as much in that group, suggesting that blood sugar variability can have multiple causes beyond just carbohydrate consistency.

Previous research has shown that consistent meal timing and composition help with blood sugar control, but this study adds new evidence that specifically the day-to-day consistency of carbohydrate intake matters. Most diabetes management advice focuses on the type and total amount of carbohydrates, but this research highlights that consistency across days may be equally important. This finding aligns with the concept of ‘glycemic stability’ that researchers have been increasingly studying.

The study included only 34 people, which is a small sample size. It lasted only 7 days, so we don’t know if these patterns hold over weeks or months. The study was observational, so we can’t say for certain that carbohydrate fluctuations cause higher blood sugar—there could be other explanations. The study didn’t account for other factors that affect blood sugar, like physical activity, stress, sleep, or medication timing. Additionally, the P-value for the coefficient of variation comparison was 0.123, which is not statistically significant, suggesting some uncertainty in that particular finding.

The Bottom Line

If you have diabetes and struggle with blood sugar control, try to eat a similar amount of carbohydrates each day rather than varying widely from day to day. This might mean planning meals ahead and keeping carbohydrate portions consistent. However, this is a preliminary finding from a small study, so discuss this approach with your doctor or diabetes educator before making changes. The evidence is moderate—promising but not definitive.

This research is most relevant for people with diabetes who have higher average blood sugar levels despite taking medication. It may be less relevant for people whose blood sugar is already well-controlled. Anyone considering dietary changes should consult their healthcare provider, especially if they take diabetes medications, as changing eating patterns might affect medication needs.

If you start eating more consistent amounts of carbohydrates, you might notice improvements in blood sugar readings within days to weeks, depending on your individual response. However, meaningful improvements in long-term blood sugar control (measured by HbA1c tests) typically take 2-3 months to show up.

Want to Apply This Research?

  • Track your daily carbohydrate intake in grams or calories for at least 2 weeks. Calculate the standard deviation or range (highest minus lowest) of your daily carb intake. Aim to reduce this variation by keeping daily carbohydrate intake within a 50-calorie range if possible.
  • Set a target carbohydrate amount for each day (for example, 150 grams) and plan meals the night before to hit that target consistently. Use the app to log meals and get real-time feedback on whether you’re staying within your carbohydrate consistency goal.
  • Compare your blood sugar readings (if using a CGM or regular glucose monitor) with your carbohydrate consistency score weekly. Track whether weeks with more consistent carbohydrate intake correlate with better blood sugar numbers. Adjust your target carbohydrate amount based on what works best for your individual response.

This research is preliminary and based on a small study of 34 people over 7 days. It shows an association between carbohydrate intake consistency and blood sugar levels, but does not prove cause and effect. This information is for educational purposes only and should not replace professional medical advice. Before making any changes to your diet or diabetes management, consult with your doctor, registered dietitian, or diabetes educator. If you take diabetes medications, changing your eating patterns may affect your blood sugar and medication needs. Never adjust medications without medical supervision.