Mental ill-health across the continuum of body mass index

Abstract

BackgroundSeveral studies have found a non-linear relationship between mental ill-health and BMI with higher rates in both the underweight and the obese. This study evaluated the shape of the relationship between BMI and distress, suicidal ideation and self-reported mental ill-health conditions in a large population sample.MethodsData were drawn from the South Australian Monitoring and Surveillance System (SAMSS) for the years 2002 to 2009 (n = 46,704). SAMSS monitors population trends in state and national risk factors and chronic diseases. Samples are drawn from all households with a functioning number in the Australian White Pages. Computer assisted telephone interviews collected information on self-reported height and weight, demographic and health behaviours. Respondents completed the Kessler Distress and suicidal ideation scales and reported specific mental ill-health conditions. BMI was categorized into deciles to allow for assessment of the shape of any associations with other variables. Logistic regression was used to examine associations between each mental ill-health condition and BMI-decile controlling for age in the base model. This was followed by a full model that added SES and the health-adverse coping behaviours of smoking, alcohol and physical activity to test for changes from the base model.ResultsNon-linear associations were observed between BMI-decile and mental ill-health but statistically significantly greater odds of mental ill-health were observed only in the obese and not in the underweight after controlling for age, health-adverse behaviours and socioeconomic status. The association between BMI and mental ill-health might best be described as 'threshold'. Elevated odds were apparent for middle-aged persons, whereas younger and older individuals had a significantly lower odds of having a mental ill-health condition.ConclusionsIn conclusion, this study has provided no support for the hypothesis of increased mental ill-health problems in the underweight but it has demonstrated the non-linear relationships between BMI and mental ill-health and between BMI and health-adverse behaviours. Non-linear relationships with BMI need to be recognized and addressed during analysis.

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.…”

“…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].…”

Associations Between Anxiety Disorder Diagnoses and Body Mass Index Differ by Age, Sex and Race: A Population Based Study

“…For instance, a study including 1,584 young Nigerian adults found no significant correlation between various subsets of anxiety and BMI [23], whereas a symmetrical U-shaped relationship between psychological distress and BMI status was noted in a Mediterranean Spanish population [28]. After controlling for age, Kelly et al only found significantly greater odds of mental illness in the obese and not in the underweight among 46,704 Australian subjects [29]. Hence, while it appears that race may have a modulating effect on the interaction between anxiety and BMI, other variables may play equally important roles including socioeconomic conditions, lifestyle, geographical location, and cultural differences.…”

Effects of a Two-Month Training Period on Soldiers’ General Health, Social Physique Anxiety, and Body Mass Index

“…In the present study, both military programs and sports programs and physical education activities do not seem to have sufficient intensity and duration to change the BMI of soldiers. The exercises and activities affecting the BMI should be based on Vo 2max and the maximum heart rate and be programmed individually (33). In addition, the BMI is a variable that interacts with several factors, including heredity, physical activity, inflammation, sleep and circadian rhythm, stress, and meals, and cannot be explained only by one factor.…”