But a week seems too long to gain it back unless you weren't measuring very often.
I'd love to track blood pressure, pulse, and weight religiously but it's hard to remember to do any more than highly irregularly, and the app I use for bp and weight can't track pulse.
I was wearing a HRM tracker for two of the interviews, but I didn't turn it on any activities to track frequent metrics. Heart rate was elevated for the entire interview, like I was briskly walking. In my hardest Google interview, my heart rate was at its peak.
Let's say you had 5 interviews over the course of five days, each lasting 5 hours. You presumably lost 1800 grams (around 4 lbs) of fat during that time, which would require energy expenditure of 37000 joules. Let's also assume you ate the same as you usually do for weight maintenance.
If you spent all that energy during the interviews, it would require sustained power output of 740 watts over your usual energy expenditure.
If you spent all that energy during waking hours (let's say 16 hours a day), it would require power output of 230 watts over usual energy expenditure.
And finally, if you spent that energy during entire day, it would require power output of 155 watts over usual energy expenditure.
For reference, energy expenditure that would amount to 2000 kcal/day turns out to be around 100 watts. Losing 1800 grams over 5 days would require additional 3240 kcals on top of that.
The morning after the second interview, at Google which was intensive, I was my lowest weight ever in several years (dropped three to four pounds from five days before)
I gained the weight back after a week. But it was interesting to observe the physiological effects from interviewing. I'm not surprised to read about such physiological effects from long, mentally intensive activities.
(I thought I did well enough in my interviews but I didn't make it past the hiring committee at Google, or Dropbox)