Abstract
The relationship of obesity with mortality rate, and subsequently, the impact of weight loss on mortality, has been questioned by researchers for many years. Although weight loss in an individual with obesity can improve metabolic outcomes, the impacts on mortality are less clear. This has caused some to question the importance of weight loss because most individuals who lose weight through diet and lifestyle interventions gain all or a substantial portion of the weight back within 5 years. Furthermore, individuals who attempt to lose weight again may enter weight cycling (yo-yo dieting), which some have suggested may be detrimental to metabolism, eating behaviors, quality of life, and, ultimately, mortality rate. Beyond weight loss and weight cycling, the relationship between diet composition and dietary patterns has also been investigated for their relationship to longevity and mortality. This narrative review will examine the existing human and animal research evaluating the relationship between weight loss, weight cycling, and dietary composition on mortality and longevity, and identify research gaps that still exist.