Disease and weight loss: a prospective study of middle-aged and older adults in Costa Rica and England

Abstract

This study tests whether disease predicts weight loss among middle-aged and older adults who participate in multiple waves of longitudinal, population based surveys. There are two major motivations for this research. First, previous studies find an association between weight loss and subsequent mortality in such longitudinal surveys.1-3 If disease does predict weight loss, this could explain the link between weight loss and mortality even though, for many individuals, mild to moderate weight loss is recommended to manage hypertension,4 diabetes,5 and other cardiovascular risk factors.6 Second, the relationship between disease and weight loss in population-based surveys is central to interpreting many epidemiological studies that analyze impacts of body weight on mortality risk.7 In those studies, body weight measures are typically assumed to reflect some combination of nutrition, fitness, and overall metabolic health. However, if weight also reflects disease processes, it is not straightforward to treat body weight as a causal exposure. Instead, body weight is both cause and effect of health outcomes. In short, the relationship between disease and weight loss matters for interpreting body weight and body mass index (BMI) intelligently in epidemiological research.