I'm glad you asked this... I've been meaning to do a write up on this subject. In my research, the most compact, lightweight, high energy food I've ever come across is raw coconut oil. It's an amazing substance consisting of MCFA's (medium-chain-fatty-acids) that are rapidly converted directly into energy while bypassing the liver, unlike all other oils. In other words, it provides quick, long lasting energy, and satiates (ends hunger) at the same time...without the high, then crash you get from simple carbs. I use it daily and it it has been part of my EDC for years. NOTE: Raw coconut oil has a long shelf life (3+ years) when stored uncontaminated at room temperatuere. However, once contaminated, it will begin to turn rancid. It is best to liquefy the oil (with body heat, etc...) and pour from the jar if you are not 100% sure your spoon is virtually sterile.
Raw coconut oil also has many medicinal uses whether used internally or topically (athlete'e foot, chapped lips, wound dressing, deodorant, etc...) I have used it for all of these conditions, and have found it to work as good or better than prescription and OTC remedies...especially for athlete's foot.
I have also theorized that it can be used as gun lube and may even be the main ingredient in Frog Lube.... the manufacturer claims their product is non-toxic and even edible.