The goal of this funding opportunity announcement (FOA) is to invite research applications investigating the role of diet composition in energy balance, including studies in both animals and humans. Both short and longer-term studies would be encouraged, ranging from basic studies investigating the impact of micro-or macronutrient composition on appetite, metabolism, and energy expenditure through clinical studies evaluating the efficacy of diets differing in micro- or macronutrient composition, absorption, dietary variety, or energy density for weight loss or weight maintenance.