The relationship between healthy lifestyle behaviours and glycaemic outcomes among Iranian adults with diabetes was non-linear, a U-shaped pattern, with glycaemic benefits peaking at moderate engagement levels and diminishing at the highest levels of engagement.
Key Findings
Results
Moderate lifestyle engagement was significantly associated with lower fasting blood sugar compared to the lowest lifestyle tertile.
In fully adjusted models, moderate lifestyle engagement was associated with lower FBS (aβ = -7.36, 95% CI -13.35 to -1.38, p=0.01) compared with the lowest tertile.
The study included 3042 adults with diabetes from a nationally representative survey across all 31 provinces of Iran.
Diabetes was defined as FBS ≥126 mg/dL, HbA1c ≥6.5%, or current use of glucose-lowering medications.
The highest lifestyle tertile did not show the same magnitude of benefit, suggesting diminishing returns at the highest engagement levels.
Results
Moderate lifestyle engagement was significantly associated with lower HbA1c compared to the lowest lifestyle tertile.
In fully adjusted models, moderate lifestyle engagement was associated with lower HbA1c (aβ = -0.27, 95% CI -0.46 to -0.07, p=0.00) compared with the lowest tertile.
Suitable glucose management was defined as HbA1c <7%.
The Composite Lifestyle Index (CLI) was derived from diet, physical activity, smoking, and alcohol consumption.
The CLI was categorised into tertiles representing the lowest, moderate, and highest engagement in healthy lifestyle behaviours.
Results
Improving from the lowest to moderate CLI tertile was associated with 1.37 times higher odds of achieving suitable glucose management.
Improving the CLI from the first to second tertile was associated with 1.37 times higher odds of achieving suitable glucose management (p=0.01).
Suitable glucose management was defined as HbA1c <7%.
This association was observed in fully adjusted models.
The highest tertile did not demonstrate proportionally greater odds, consistent with the U-shaped pattern observed.
Results
Restricted cubic spline analysis confirmed a significant non-linear (U-shaped) relationship between the continuous CLI and both FBS and HbA1c.
Non-linearity was statistically significant for both FBS (Pnon-linearity = 0.002) and HbA1c (Pnon-linearity = 0.005).
Maximal glycaemic benefits were observed at moderate CLI values.
Benefits diminished at the highest levels of lifestyle engagement.
This U-shaped pattern suggests that very high levels of lifestyle engagement were not associated with proportionally better glycaemic outcomes.
Methods
The study assessed geographic distribution of lifestyle behaviours across all 31 provinces of Iran using data from the 2021 WHO STEPS survey.
Data were drawn from the 2021 WHO STEPwise Approach to Noncommunicable Disease Risk Factor Surveillance (STEPS) survey, described as the latest available.
The survey was population-based and nationally representative.
Adults aged ≥25 who completed the third step of the STEPS study were eligible.
3042 adults with diabetes were ultimately included in the analysis.
Diabetes awareness was assessed by self-report.
Conclusions
The authors highlight that exploratory findings suggest moderate lifestyle engagement may be associated with improved glycaemic outcomes, with implications for underserved regions.
The authors call for prospective studies to evaluate whether integrating tailored lifestyle promotion into diabetes management can effectively benefit underserved regions.
The cross-sectional design limits causal inference.
The study's nationwide scope across 31 provinces enabled geographic distribution analysis of lifestyle behaviours.
The findings are described as 'exploratory,' indicating the need for further research to confirm the associations observed.
What This Means
This research studied the relationship between healthy lifestyle habits and blood sugar control in over 3,000 Iranian adults with diabetes, using data from a large national health survey conducted in 2021. The researchers created a Composite Lifestyle Index (CLI) that combined information about diet, physical activity, smoking, and alcohol consumption to measure how healthily participants were living. They then examined how different levels of healthy lifestyle engagement related to measures of blood sugar control, including fasting blood sugar and HbA1c (a measure of long-term blood sugar levels).
The key finding was that the relationship between lifestyle and blood sugar control was not a simple straight line — it followed a U-shaped curve. People who engaged in moderate levels of healthy lifestyle behaviours had meaningfully better blood sugar control than those with the lowest engagement: their fasting blood sugar was about 7.4 mg/dL lower and their HbA1c was about 0.27 percentage points lower on average. Moving from the lowest to the moderate lifestyle group was also associated with 37% higher odds of achieving good blood sugar control (HbA1c below 7%). However, the people with the highest levels of healthy lifestyle engagement did not show proportionally greater improvements — the benefits peaked at moderate engagement and then diminished.
This research suggests that even moderate improvements in lifestyle habits among people with diabetes could meaningfully improve their blood sugar management. The U-shaped pattern is an interesting and somewhat unexpected finding that may have implications for how lifestyle goals are set for people with diabetes. However, because this was a snapshot study (cross-sectional), it cannot prove that lifestyle changes caused better blood sugar control. The authors emphasize the need for follow-up studies, particularly to understand whether tailored lifestyle programs could help people in underserved regions of Iran manage their diabetes more effectively.
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Mozafari S, Ataei-Goujani H, Behgam N, Mirzad M, Karimi K, Tabatabaei-Malazy O, et al.. (2026). Lifestyle behaviours, glucose management and diabetes awareness among Iranian population with diabetes: evidence from a nationwide study.. BMJ open. https://doi.org/10.1136/bmjopen-2025-114022