Fat contains the densest concentration of energy, more than twice that of carbohydrates and protein. Thus a heaping ounceful of pure fat sets the upper limit: 255 calories.
You probably don’t want to eat Crisco or lard for your meals, however, and might want to consider our next calorie champion: nuts. Depending on the type, nuts range from 160-200 calories per ounce. In order, they are:
Then we have a whole slew of items that hover around the 100-120 calories/ounce mark. These include:
Cheese
Pasta
Candy bars (Go for the peanut M&M’s: 145 calories/ounce)
Finally, for breakfast, consider granola (120-150 calories/ounce) instead of oatmeal (80-100 calorie).