What foods are the healthiest / lowest in calories?

Veggies/fruits. Eating things from mother nature are always better than processed man made food. Eatnutrient rich, calorie low with plant based diets. Your proteins are beans, legumes, lentils, nuts/seeds, avocados. Your veggies should be alot of dark greens, followed by cruciferous veggies (broccoli, cauliflower, cabbage) and then everything else; fruits are great; water is awesome.