Thank you for your response JF.Very good how active you've kept (which sounds condescending but really isn't)
The question though. Really no simple answer at all.
Depends what you mean by the zip has gone, depends the rest of the time how have you felt (not beyond the realms you've had a bug or virus and are getting over it) might be a bit of stress over the covid thing/anything else. Could just be a lull in energy, or have you changed your diet at all, maybe lacking in a vitamin or mineral. Have you sweat much when out walking, with it being muggy, could be slight dehydration. And so on.
There are energy gels, hydration tablets, caffeine (I can't really operate without an energy boost from caffeine most days, wish I could) and so on if any of those help.
I would start with the simple things, so check you are hydrating ok first perhaps. And wouldn't hurt to try to increase your intake of foods high in potassium, so bananas, natural yoghurt, err... long list you can google or I can cut and paste into here if you wish. Might be nothing to do with that, but you won't hurt yourself having that food anyway.
I think it has been pretty muggy of late, could be something that simple?
It strikes a chord.
I drink a cup of tea when I wake, a cup of coffee perhaps a half hour later, and I probably only have maybe one, or possibly two hot drinks in the rest of the day and no cold drinks.
I say it strikes a chord because what you have said is what my wife has also said.
I just dont feel thirsty.
I also dont eat much.
Cant do breakfast, other than a few biscuits, and rarely any lunch.
I do eat a decent evening meal, as its the only time I feel hungry.
She also said the porridge you mention in your later post.
I think maybe what I could get away with when younger possibly wont work now.
I did think about the virus you mention, because back at the end of Jan, early Feb I had the most aweful cough that lasted a couple of weeks and havent really felt right since then.
I think more liquid, and porridge will be the first port of call.
Once again thanks for taking the time.