In the context of nutrition the word calories always means dietary calories, so the kilo- prefix is redundant unless discussing physics, or commenting on HN...Ooooh, ok.

The practice of indicating kcals as "Calories" always seemed to be an American thing to me. I don't know how widespread this is outside the US but there are plenty of countries that use "kcal" in nutritional tables and such. People will still colloquially confuse calories and kilocalories a lot but that's largely due to bad translations (similar to mistranslating short billions).

In Poland you write "100 kcal" but say "100 kalorii" unless it's in scientific context.

People everywhere mix those 2 regularly and nobody is confused. You don't say you go out for a run to burn some kilo calories and so on. Sometimes places like HN are needlessly pedantic

If someone explicitly writes "160 000" calories I'm going to assume they meant 160 kcal.

Can you show me a representative sample of places where English speakers refer to [unit of energy] burned by exercise and mean anything else other than kilocalories while saying anything else other than calories?

No, you can't, you're showing hypercorrection and lack of fluency.

Actually, I noticed it because the OP wrote kcal in one place and calories in another and since they were using large units I had to read the sentence twice to make sure they meant the same thing. I don't have a problem with the fact that we have a unit that means something in one context and 1000xsomething in another as long we're consistent in naming (only calories or only kcal in the context of diet). And of course I didn't mean to be mean (no pun intended) to the OP - being consistent is good but this is such a minor thing that we could safely ignore and it won't affect our lives at all - now I even feel sorry I paid attention to that.

Yes, sorry. kcal not cal.