So the main problem would be nutrient absorption, and there would be a number of problems that would impact it, from literal surface area of your digestive system, to current bacterial populations etc. etc. These problems matter less in a 24 hour window when you are far less likely to hit the same thresholds eating a reasonable amount of food. But basically, you could not effectively break down and absorb all the nutrients quickly enough, and you would have pretty nasty shits/vomiting.
But, let's say somehow you could, and somehow your body ended up storing a bunch of fat. In general, the second half of your statement is totally doable because the human body absolutely kicks ass at energy storage and expenditure. https://www.sciencealert.com/the-true-story-of-a-man-who-sur...
So why can't I eat a month's worth of calories in one go and then fast for the rest of the month with water and multivitamins?