I did a or 16+ mile day I believe, one time, about six-seven years ago. I didn't stop for lunch or a break, I was trying to beat a storm in Oct. Snowing all around me and on me lightly and here I was, on the wrong side of the mountain. When I finally stopped for a break in the afternoon, a little before 4:00, I was barely making it up little rises in the trail, around the north side of Thousand Island Lake in the Sierra, after coming from Iron Creek, just south of Hemlock Crossing, which is just east of Yosemite. I don't think I drank that much water all day either. Anyway, didn't really bonk, just had no power. When I stopped below the outlet of Thousand Island, I ate a Genisoy brand bar and drank some water. I had a watch with me on this trip, about 45 minutes later, I was striding uphill and jogging on the downhills and flat ground. In the 7.6 miles to the trailhead, according to my Tom Harrison map, I made it there in two hours.:) Felt fine, ate dinner at moms at 9:30 that night. Pooch kept up too. I believe in those bars, just can't find them anywhere now since last year.