[mattkrause]

That paper has some serious issues.

On the practical side, the prisoners were ordered. Judges tried to break for meals after processing a whole 'batch' of prisoners from a specific prison. Within a prison block, those with lawyers went before those representing themselves, and lawyers also ordered their cases however they wanted. As you might expect, prisoners having counsel fared better than those without.

Additionally, they measured "time elapsed from a meal" in two ways: actual wall time (in hours/minutes/seconds/etc), and case order. Both measures were individually significant, but when both were put into a model, only the ordinal one remained significant. This suggests--to me, at least--that the result isn't due to a physiological process: blood sugar levels vary continuously and don't "jump" from case to case.

There was a rebuttal letter in PNAS shortly after it was published.

Edit: HobbyJogger covered most of this first. Thanks!