I've been on the keto diet for just over two years now, and since adopting it, I've found that I can work out before breakfast without any problems. I know keto isn't for everyone, but I've discovered that it allows me to utilize stored fat much easier, hence the ability to engage in a heavy lifting session 12-14 hours after my last meal. I've also found that I like being able to lift before eating as I don't have to wait for breakfast to digest. Food engages the parasympathetic nervous system, which is why people can feel sluggish right after a meal or develop indigestion trying to be active too soon after a meal. I get my workout in and then I'm really ready to pig out afterward!