Unintentional weight loss: Most risk factors do not differ between individuals with a healthy weight and those with overweight or obesity

Background: Unintentional weight loss (UWL) is an important clinical indicator of malnutrition risk. Risk factors for UWL may vary by body size, typically measured by body mass index (BMI), which complicates identification in individuals with overweight/obesity. Methods: Data from ~125,000 adults (>18 years) in the Dutch Lifelines cohort were analysed to examine whether associations between 21 potential risk factors spanning sociodemographic, psychological stress, disease, dietary, and quality-of-life domains and UWL differ by BMI group. Participants were classified as having a healthy weight (45.8%) or overweight/obesity (54.2%). Multivariable Poisson regression models estimated prevalence ratios for UWL, with sensitivity analyses to test robustness. Statistical significance was set at p<0.05.
Results:  UWL was reported by 4.9% of participants with a healthy weight and 2.7% of those with overweight/obesity. Ten risk factors (gender, employment, psychological stress, chronic obstructive pulmonary disease, depression, physical problems, and poor perceived health, vitality, emotional well-being, and social functioning) showed effect modification by  BMI group (p<0.1), with most factors positively associated with UWL in both groups and generally more pronounced among individuals with a healthy weight. Gender showed a reversed association: females were more likely to report UWL in the healthy weight group than in the overweight/obesity group. In sensitivity analyses, only education, psychological stress, and physical problems retained significant effect modification.
Conclusion:  Most risk factors for UWL were consistent between BMI groups. However, differences in the associations with education, psychological stress, and physical problems suggest that although the factors are similar, their impact and clinical relevance may differ by BMI.
Keywords: Malnutrition risk; Sociodemographic factors; Diet quality; Psychological stress; Chronic disease; Quality of life.