Associations of morbidity in the underweight

Abstract

Background/Objectives: There is little research on the demographic characteristics and morbidity of people categorized as 'underweight' from their body mass index (BMI) although they have often been shown to have greater mortality. This uncertainty makes it difficult to determine whether to include or exclude these individuals when estimating the health and mortality impacts of BMI. This project compares the demographic characteristics and morbidity patterns of the underweight with those of acceptable weight and the overweight. Subjects/Methods: Data on 10 243 community-living residents from the Health Survey for England (2003) were used. Logistic regression models were constructed to compare demographic, biochemical and anthropometric factors in the underweight (BMIo18.5) with those classified as acceptable weight (BMI 18.5-24.9) or overweight (BMI 25.0-29.9). Results: Univariate analyses found, when compared with other BMI categories, underweight individuals were significantly younger, more likely to smoke, alcohol abstainers, inactive, poorer and were less likely to be ethnically white (all Po0.001). U-shaped relationships between BMI and activities of daily living, respiratory disease, physical activity and mental health variables were seen. In multivariate analysis, the fewest number of significant differences in demographic and morbidity factors were between the underweight and those of acceptable weight. Conclusions: We recognize that these are cross-sectional data and exclude individuals in institutional settings, but these findings are important. Overall, we could not conclude that the underweight were less healthy than individuals in the other BMI categories. We cannot therefore recommend that the underweight should be excluded from analyses that examine the effects of obesity on mortality.

Self-reported general health and Body Mass Index: a U-shaped relationship?

“…We observed that U-shaped relationships between BMI categories and health are noted in some literature and presented in results but without emphasis [though see 27,34]. Controlling for socioeconomic, health behaviour and deprivation variables, using the Health Survey for England (2006-08), compared with persons of normal weight, we find significantly increased likelihoods of persons to report poor general health for both underweight and obese BMI categories and a slight but significant increase for persons who are overweight.…”

“…The lack of research into persons of underweight BMI in comparison with those whose BMI is higher than normal weight has been noted [27,34]. This work reveals demographic and health differences between people of different BMI categories and nonlinear associations between BMI and mental health.…”

“…This work reveals demographic and health differences between people of different BMI categories and nonlinear associations between BMI and mental health. Using the Health Survey for England (HSE), U-shaped relationships were found in univariate models between BMI and activities of daily living, respiratory disease, physical activity and mental health variables [27]. However, later work using an Australian sample found significantly greater odds of mental ill-health in the obese but not in the underweight, controlling for age, health-related behaviours and educational achievement [34].…”

“…Why those who are underweight have an increased risk of mortality is debated but it is suggested that persons in this BMI category may have undiagnosed disease [27].…”

“…This paper investigates the association between BMI category and self-reported health in a representative sample of the residential adult population in England. We build on previous analyses using the HSE [27] to model the likelihood of poor general health across BMI categories whilst controlling for factors expected to influence health including socioeconomic characteristics, health-related behaviours and area deprivation.…”