Can fasting help athletes hold their breath longer?
This was basically the question posed to Peter Attia by his friend, Justin Lee, a world-class freediver and spearfisherman who is already hard at work training for the 2020 World Championships next Fall.
Yes, it appears like it can!
In one instance, the 13 participants performed a maximal breath-hold one and a half hours after their first meal of the day. Serving as their own controls, they also performed the same test after an overnight fast, which amounted to 13 hours since their last meal, on average. 
The results weren’t subtle. The average duration of the max breath-hold in the fasting condition (4:41) was 50 seconds longer than in the fed condition (3:51). From a statistical standpoint, it’s not often that you see a p-value less than 0.001 in a study with only 13 people, but that’s what the investigators found after crunching the numbers. Unsurprisingly, the investigators concluded that fasting is beneficial for STA* performance in elite divers.
*STA = Static apnea (STA) is a discipline in which a person holds his or her breath (i.e., apnea) underwater, and more or less without moving (i.e., static), for as long as possible.
Here is the full email from Peter Attia with more information on the study itself.
Lastly, I’m not sure how many of you are freedivers or are looking to increase the amount of time you can hold your breath but I thought this was a fun experiment!