Is junk food exhausting?

I’m Canadian, and so I like to pour maple syrup on my vanilla ice cream, and I ate many mighty bowls of that sweet slop as a kid. As an adult, that would wreck me: I’d feel gross, fragile, and exhausted for hours. Which I know because I’ve tried it, of course! (“Why are you hitting yourself?”)

There’s a vast gulf between what kids and olds can get away with eating. And in the oldest of the old, a lousy diet is linked to fatigue (Davis, Azzolino), and that vulnerability of the elderly is an interesting clue that junk food might cause fatigue for more than just a few hours of strained digesting after a reckless meal.

Another clue: there’s some evidence that junk food is a medium-term risk factor for pain. It was a bit startling to see evidence that a poor diet might inflame pain in just weeks or months. Could the same be true of fatigue? A reader asked, and then I wanted to know too.

I haven’t been able to find clear evidence of this, but it is highly plausible in broad strokes. Pain and fatigue have a lot in common physiologically, probably mostly through the shared mechanism of inflammation. There is a mountain of evidence that poor health is both fatiguing and painful on a timeline of years.

But is any diet junky enough to cause fatigue beyond the acute effects of straining to digest it? If a healthy person starts a junk food diet in August, will all their days be more fatigue-filled by Halloween?

And could the “ultraprocessed foods” in particular do this? They may be extra “proinflammatory” (Asensi), and they are probably linked to depression and anxiety (Hecht), and even cognitive decline (Bhave) — though it’s unclear if they are causally linked. (The UPFs are also a magnet for profitable fear-mongering, and they may well be guilty only by association with the many other health headwinds in people who live on instant noodles.)

Whether junk food acts like a mildly exhausting poison in otherwise healthier adults remains unknown. But it does seem likely.