The obesity paradox is a phenomenon where high body weight is associated with poor health during the life course but paradoxically lower mortality at older ages. Many researchers, including me, suspect that this is because lower body weight at older ages is associated with frailty rather than health but it’s been difficult to show with population survey data.
In a paper published in The Gerontologist a few years ago, my colleagues and I applied a joint generalized growth mixture-proportional hazards survival model and found that weight gain among older adults has little detrimental effects on mortality while weight loss is a powerful predictor of mortality.