Volumetric is a concept developed by Penn State University nutrition and obesity researcher Dr. Barbara Rolls (I was honored in the same research group when I was at Penn State). It is all about energy density – the number of calories per volume of the foods. Emphasizing low energy-density foods results in feeling full longer with fewer calories, which leads to weight loss over time. Foods with low energy density tend to have lots of water and/or dietary fiber, neither of which provide calories but do provide volume. Good examples of low energy density foods include a salad made with lots of fruits and vegetables, adding protein foods, such as beans, cheese, chicken, steak, and balsamic vinegar dressing; a smoothie made with spinach, beet, cucumber, tomato, apple, flaxseed powder, and whole Greek yogurt; a soup made with vegetables, beans, and ground turkey. On the contrary, high energy density foods can trick you to eat a lot of calories quickly because they are low in volume. Good examples of high energy density foods include energy bars, ice cream, peanut butter pretzels, etc. Overall, when you focus on low energy density foods, you will lose weight easily even feeling full and satiated.