There are several types of bars of interest to hikers that go by different labels: energy, snack, candy and meal replacement bars. No further attempt will be made to further delineate or define these different types other than to observe that “energy” bars are commonly high in carbohydrates, low in protein and fat.
In brief, here is what I have found while seeking out the truth about energy bars and related products:
Imbibing “energy” bars, drinks or concoctions, by themselves, do not make one more energetic!
Despite the labels (power, energy, etc.) and the hype by manufacturers, don’t buy into the implied claims that “energy” bars are significantly better on the trail than a balanced diet of regular food. [Qualification: if you are not stopping regularly to rest and to eat regular food, anything with carbohydrates will give you some quick energy.]
The crux of the matter is whether or not there is reliable evidence that the unique blends of nutrients/ingredients in various “energy” bars, drinks or concoctions provide increased energy and stamina. To my knowledge, such evidence from independent sources is not available. I will allow that nutrition science might someday bless some form of specialized “energy” food and drink. I will also grant that better quality energy bars (e.g., containing organic fruits and nuts and balanced in their proportion of fat, carbs and protein) are generally more nutritious than eating a regular candy bar. Also, if one is not stopping regularly to eat high quality, regular food (e.g., when adventure racing or ultrarunning), energy or meal replacement bars can provide relatively balanced nutrition for the short term.
Any of the four types (candy bars, energy bars, snack bars, meal replacement bars) are useful for day hikes and shorter backpacking trips. I generally toss in a couple for the sake of variety and for emergency rations. For longer backpacking trips, I include some meal replacement bars, especially bars that taste good and are rich in antioxidant fruits, nuts, electrolytes and complex carbohydrates.
This is my take on this controversial subject. What is yours.