Investigating the relationship between inhibitory control and dietary adherence among patients with type 2 diabetes mellitus based on subjective and objective measures

The study addresses the challenge of low dietary adherence among patients with T2DM, despite dietary management being central to glycemic control and complication prevention. Inhibitory control, a core executive function enabling resistance to temptations and appropriate decision-making, may influence dietary behaviors requiring long-term self-regulation. Prior work links poorer inhibitory control with unhealthy eating and obesity, but evidence among T2DM patients is scarce. The research aims to determine whether inhibitory control, measured both subjectively (BRIEF-A) and objectively (SST for response inhibition and Stroop for interference inhibition), is associated with dietary adherence in T2DM patients and whether it predicts adherence beyond demographic and clinical factors.

Prior studies indicate inhibitory control is key to regulating food intake, with deficits linked to overeating, preference for high-calorie foods, weight gain, and obesity. Inhibitory control has been shown to positively predict healthier intake (e.g., fruits/vegetables) in overweight/obese populations. Training inhibitory control can reduce preference for high-calorie foods and snack consumption in experimental settings. However, past research largely focused on restrained eaters, eating disorders, and obesity, with limited investigation among chronic disease populations like T2DM that require long-term dietary management. Temporal self-regulation theory posits executive functions like inhibitory control directly/indirectly influence health-promoting behaviors. Task-based measures (SST, Stroop) and questionnaires (BRIEF-A) capture different aspects of inhibitory control; task-based measures are objective but may lack ecological validity, whereas questionnaires reflect everyday functioning. Combining both approaches can provide complementary insights. Evidence suggests food-specific inhibitory control may be more relevant to dietary behavior than general inhibition, highlighting a need to assess different inhibitory domains in T2DM.

Design: Cross-sectional descriptive study conducted March–September 2022 across endocrinology departments of three tertiary hospitals in China using convenience sampling. Participants: 393 adults with T2DM meeting 1999 WHO diagnostic criteria, disease duration ≥6 months, age ≥18, normal/corrected vision with normal color perception, normal finger function, MoCA ≥25, able to communicate and consent. Exclusion: cerebrovascular/CNS injury history or inability to complete questionnaires/tasks. Sample size justification targeted minimum N=82 (effect size 0.3, alpha 0.05, power 0.80). Procedures: Phase 1 involved informed consent, cognitive screening (MoCA, 8–10 min), and questionnaires (sociodemographics; BRIEF-A; Dietary Behavior Adherence Scale), completed in a quiet environment; items randomized to reduce common method bias; data checked for completeness. Phase 2 involved objective inhibitory control tasks; 108 participants opted in, received standardized instructions and practice; formal trials were self-performed. Ethics approval obtained (Air Force Medical University, No. 202206-02). Measures: - Sociodemographics: age, gender, education, monthly family income, diabetes duration, hypoglycemia history in past year, diabetic complications, treatment method, BMI. - Cognitive screening: Montreal Cognitive Assessment (MoCA), 11 items across 8 domains; total score 0–30; ≥25 considered normal cognition. - Dietary adherence: Dietary Behavior Adherence Scale for Patients with T2DM (23 items; five dimensions: diet self-regulation; carbohydrate and fat adherence; oil and salt adherence; fruit and vegetable adherence; cooking and eating habits). Items rated 1–5; higher scores indicate better adherence. Reliability: overall Cronbach’s α=0.891; subscales α=0.729–0.830. - Subjective inhibitory control: BRIEF-A inhibitory control subscale (8 items); T-scores with higher values indicating greater impairment; Chinese version validated; Cronbach’s α=0.797. - Objective inhibitory control: • Stop Signal Task (SST): 200 trials (140 go, 60 stop; 30% stop). Go signals were letters “f”/“j” with corresponding keystrokes; stop signal was a red dot appearing after a stop-signal delay (SSD). SSD adaptive staircase (initial 250 ms; ±50 ms adjustments) aimed for ~50% successful inhibition. Stimulus timing: fixation 250 ms; max presentation 1250 ms; 1000 ms inter-response interval. Metrics: Go reaction time (GoRT), SSD, and SSRT calculated by race model (SSRT = mean GoRT − mean SSD); smaller SSRT indicates better response inhibition. • Stroop task (color-word): 256 trials, 75% congruent and 25% incongruent, four color words (red/blue/green/yellow); responses mapped to keys F/G/J/K. Metric: Stroop effect (incongruent minus congruent RT); smaller values indicate better interference inhibition. Statistical analysis: Data entry via EpiData 3.0; analyses in SPSS 23.0. Descriptive statistics summarized sample characteristics and key variables. Group comparisons of dietary adherence by sociodemographics used independent t-tests or one-way ANOVA (normality assumed). Pearson correlations examined associations between inhibitory control measures and dietary adherence. Hierarchical regression tested whether inhibitory control predicted dietary adherence beyond demographics/clinical variables. Significance threshold p < 0.05.

- Sample: 393 T2DM patients (78.9% male), mean age 51.55 ± 11.45 years; mean diabetes duration 9.46 ± 6.26 years; 41.98% reported hypoglycemia in the past year; over half were overweight/obese. - Group differences in dietary adherence: Significant differences by age (F(2,390)=6.94, p=0.001, η²=0.04), gender (t=-2.59, p=0.010), education (F(3,389)=11.05, p<0.001, η²=0.08), hypoglycemia history (t=2.86, p=0.005), and BMI (F(3,389)=4.71, p=0.003, η²=0.04). Generally, older age, female gender, higher education, and hypoglycemia history were associated with better adherence; higher BMI associated with poorer adherence. - Subjective inhibitory control (BRIEF-A inhibitory control T-scores): Negatively correlated with total dietary adherence score and all subscales (e.g., total r=-0.312, p<0.01; fruit/vegetable r=-0.250, p<0.01; oil/salt r=-0.196, p<0.01; carbohydrate/fat r=-0.227, p<0.01; diet self-regulation r=-0.221, p<0.05; cooking/eating habits r=-0.312, p<0.01). - Hierarchical regression (dietary adherence as outcome): After controlling for demographics/clinical variables, inhibitory control significantly predicted dietary adherence: overall model F(19,373)=7.096, p<0.001; ΔR²=0.069; ΔF(1,373)=35.219, p<0.001. Inhibitory control coefficient B=-0.016 (SE=0.003), β=-0.274, 95% CI (-0.022, -0.011), p<0.001 (higher impairment associated with lower adherence). - Objective inhibitory control: • Stroop effect: Significantly negatively correlated with carbohydrate/fat adherence (r=-0.244, p=0.014); not significantly associated with other subscales or total score. Hierarchical regression for carbohydrate/fat adherence showed Stroop effect added significant variance: overall model F(19,81)=2.848, p=0.005; ΔR²=0.060; ΔF(1,81)=8.137, p=0.006. • SST (SSRT): No significant correlations with total or subscale dietary adherence (all p>0.05).

Findings indicate that inhibitory control is meaningfully associated with dietary adherence in T2DM. Subjective everyday inhibitory control deficits (BRIEF-A) were linked to poorer adherence across all dietary domains and remained a significant predictor after adjusting for demographic and clinical factors, suggesting that patients’ perceived inhibitory control in daily life has strong ecological relevance for adherence behaviors. Objectively, better interference inhibition (smaller Stroop effect) predicted better adherence specifically to carbohydrate and fat intake, aligning with the notion that resisting interference from tempting food cues is important for maintaining low carbohydrate/fat diets. The lack of association between general response inhibition (SST with non-food stimuli) and adherence suggests that food-specific or interference-related inhibition may be more pertinent to dietary self-regulation than domain-general motor stopping. Clinically, assessing inhibitory control could help identify patients at risk for poor dietary adherence, and interventions targeting inhibitory control may improve adherence. The results support integrating cognitive training focused on inhibitory processes into diabetes self-management programs.

This study provides convergent evidence, using both subjective and objective measures, that inhibitory control is a predictor of dietary adherence among patients with T2DM. Subjective inhibitory control deficits were associated with poorer adherence across dietary domains, and objective interference inhibition predicted adherence to carbohydrate and fat guidelines. These findings highlight inhibitory control as a potential intervention target to enhance dietary self-management. Future work should test whether inhibitory control training improves adherence and glycemic outcomes, and explore neural mechanisms underlying inhibitory control differences in T2DM.

- Generalizability is limited by recruitment from only three hospitals in China. - Cross-sectional design precludes causal inference between inhibitory control and dietary adherence. - Objective tasks assessed general inhibition with non-food stimuli; food-specific inhibition may be more relevant. - Future studies should employ longitudinal designs and integrate neurophysiological/neuroimaging (EEG, MRI) methods to elucidate mechanisms and causal pathways.