Is there any difference between 100 calories of peanut butter and 100 calories of bread?

Energy wise, NO!: 100 calories of anything is 100 calories and will require the exact same amount of exercise to burn those calories (approximately 1 mile walk/run in a 150lb individual). However, 100 calories of fat are more easily stored as adipose tissue than 100 calories of carbohydrate like bread which will need to be biochemically altered to be configured into adipose tissue. But alas, this is another topic.