From the queen of workouts herself, Jillian Michaels is busting myths about protein bars and how they work to fuel your body. People use protein bars as pre-workout snacks or meal replacements. According to Jillian, it is easy to overlook the amount of calories and sugar in these bars because people concentrate on the level of protein they offer. Snack protein bars should be 220 calories or less while meal replacement bars should be at a maximum of 400 calories. Although she does not provide an estimate on how much sugar each protein bar should have, it is important to study the ingredients. Jillian says to look for bars that have isoleucine, leucine and valine. These are great for muscle growth.