A Chicago-area study of adults with borderline personality disorder found that higher consumption of foods rich in saturated fat and added sugar was linked to greater motor impulsiveness, and that intake of saturated fat alone was associated with increased risk-taking on a gambling task. The findings, reported in Nutritional Psychiatry, did not show a connection between diet and the overall severity of BPD symptoms.
Borderline personality disorder is marked by intense emotions, unstable relationships and self-image, and impulsive behaviours. While specialized psychotherapy helps many, about half of adults with BPD do not respond fully, highlighting a need for additional approaches to treatment.
Researchers say nutrition may be a potentially important but overlooked factor. Diets high in saturated fat and added sugar—common in processed foods—have been linked in other work to greater impulsivity and may influence the brain’s reward systems and inflammation, which could affect emotional regulation.
Authors Sophie Boutouis and Jon E. Grant of the University of Chicago set out to examine whether saturated fat and added sugar intake relate to BPD symptoms and to differences in diet across demographic groups. They hypothesised that higher intake of these nutrients would correspond to more severe BPD symptoms, more co-occurring psychiatric disorders, poorer decision-making and greater impulsivity.
The participants came from the Chicago area and were adults enrolled in a clinical trial testing the antipsychotic lumateperone as a treatment for BPD. To participate, they had to be aged 18 to 65, have a primary diagnosis of BPD and exhibit symptoms above a defined severity threshold; individuals with schizophrenia, bipolar I disorder or moderate-to-severe substance use disorders were excluded. The analysis used data collected at the trial’s first visit, before treatment began.
Of 60 eligible participants, 57 completed the diet questionnaire and were included in the analysis. Their average age was 32, about 72% were women, and roughly half identified as white.
Participants reported how often they had eaten various foods high in saturated fat and added sugar over the past year using the Dietary Fat and Free Sugar – Short Questionnaire, which yields separate scores for foods high in saturated fat, foods high in added sugar, and foods high in both. They also completed the Barratt Impulsiveness Scale and the Cambridge Gambling Task, a computerised test of decision-making in which risk-taking is measured by betting. Clinicians assessed co-occurring psychiatric disorders and suicidal thoughts using the Mini-International Neuropsychiatric Interview and rated BPD symptom severity over the previous week.
After accounting for age, race, depression and suicidal thoughts, those who ate more saturated fat tended to bet more on the gambling task, indicating greater risk-taking. Those who ate more foods high in both saturated fat and added sugar tended to report greater motor impulsiveness. By contrast, added sugar intake on its own was not linked to impulsivity, decision-making or symptom measures.
Diet did not show an association with the overall severity of BPD symptoms or with other aspects of impulsivity or decision-making. The authors noted that diet was assessed over the past year while symptom severity was measured over the past week, which may help explain the lack of a broader link.
Demographic differences emerged: Black participants reported higher saturated fat intake than some other groups, and those who ate more foods high in both fat and sugar tended to be older. Participants without depression or recent suicidal thoughts reported higher saturated fat intake than those with these conditions, while those with a substance use disorder reported lower added sugar consumption.
“Saturated fat and added sugar consumption in the past year may be associated with domains related to BPD (i.e., impulsivity, risk-taking behavior). As causality cannot be inferred due to the cross-sectional design of this study, future research should examine whether improvements in nutrition may lead to reductions in BPD symptoms,” the study authors concluded.
The study adds to the scientific understanding of BPD, though it features a relatively small, treatment-seeking sample and does not account for participants’ medication or psychotherapy status. Its cross-sectional design also means causal inferences cannot be drawn, and unmeasured factors such as body mass index or physical activity could influence the findings. Diet was self-reported over a full year, which may be prone to recall inaccuracies or underreporting of unhealthy foods.
The paper, “Associations between dietary fat and sugar intake and impulsivity in adults with borderline personality disorder,” was authored by Sophie Boutouis and Jon E. Grant.
