Sorry, keto crowd, science doesn't substantiate the hype.
Exogenous ketones – waste of money or worth it for some? I guess it depends on why you're using them.
Right now, they're relatively new on the scene. There's only very slight evidence they're having an impact on performance enhancement, and very little (if any) evidence they're aiding fat loss.
Science is notoriously slow with answering these questions and that's frustrating for all of us, especially when it means the overzealous people of anecdotes fill the void. Add an MLM (multi-level marketing) component to it and you have a big mess of novelty bias, research gap, bioscience, and monetary motivation to contend with.
I will say this: If you're using the keto diet to lose weight, the use of exogenous ketones does NOT make much sense. If you eat the ketones, your body sees no need to make its own ketones. You may still be in ketosis on your ketometer, but are those ketones you're making from your own fat stores or from the stuff you just drank?
Where they may have some utility is getting into ketosis faster, exercising under ketogenic conditions, and experiencing satiation.
We know that protein is THE most satiating macronutrient. Some evidence suggests once the body starts making ketones they're on a par with protein in satiating potential.
Exogenous ketones may play a role in controlling SHMEC (sleep, hunger, mood, energy, cravings) in that all-important three days to get into ketosis. I call that the AKZ (the Almost Keto Zone). Most people who try keto can never get past these three miserable days and therefore end up getting fatter. They cut carbs and then binge within three days and repeat that cycle again and again.
So, I think there are some possible beneficial areas to explore the use of exogenous ketones, but right now the science doesn't substantiate the hype.
It's also useful to note that the ketosalts widely available currently have shown less potential in research compared to the ketone esters which, if I am not mistaken, are not available commercially.