I was about to post “think about dehydration” and see that skywalker has already mentioned it.
I felt really lightheaded – and hungry- when driving this evening, kept thinking “shall I stop” but it wasn’t that bad and I didn’t see anywhere convenient until I was almost back. Got in, drank two glasses of water in quick succession, and feeling hungry had gone,
I’d probably had the same amount of liquid as normal, but the impact of walking for three hours in hot sun** had counteracted that,
**Hot sun for the UK, probably equate to a chilly afternoon for some antipodean posters!