Diet Quality and Weight Change in Adults Over Time: A Systematic Review of Cohort Studies

This systematic review examines the relationship between diet quality and weight gain in adults over time and is an update of our previous review of the same topic. The goal was to synthesise the best available current evidence on diet quality and weight change within longitudinal analyses. The inclusion criteria were case-control or cohort studies, and adults aged ≥18 years. The dependent variable was diet quality indexes and the independent variable was any measurement of body weight. The current systematic review identified 16 studies published between 1970 and 2014. Of these, eight were published since our last review. The findings of these recent studies confirm the results of our previous review, that higher diet quality is associated with relatively lower prospective weight gain, as well as a lower risk of becoming overweight or obese, compared with poor diet quality. Across the 16 studies, it appears that the diet quality indexes based on foods alone, or food and nutrient components, are more predictive of weight change. However, further research is needed to confirm this. Additionally, high-quality analyses that assess change in diet quality over time are needed.