My wife works a weird 12 hour schedule as a nurse. Sometimes she's so busy that she's unable to eat. So, the next day she will eat and tell me about how she's still "eating yseterday's calories and hasn't toufhed today's calories yet".

That sounds like a license to kill to me. I've come in under my calories many times and the thought of adding the previous da's calories has never crossed my mind.  I can see budgeting calories for a splurge later the same day but not keeping calories from a previous day for later use.

Am I off base in saying this makes no sense?

When you eat a meal, your liver processes all the nutrients in conjunction with your other digestive organs (pancreas, intestines). The liver has the ability to store up to 100g of glucose. It is also the only organ that processes and stores fructose as your other bodily cells can only use glucose. When you fast - or not eat in a long period of time - your body will first run on the stored glucose in your liver and locally in the muscles. After about 8 hours when most glucose is expended, your body dramatically releases HGH which tells the body to preserve muscle and tells all your fat cells to release their fatty acids to be used as energy. The longer you go in a fasted state (>12 hours) the more HGH that is released and the more body fat you burn. This is what I do on a daily basis and I also do 24 hour fasts with fasted training. However, when I eat I eat very nutritionally dense foods and no simple sugars or man-made fats.

The catch is the body must be used to restricted food intake and fasting to tune and "train" it that it need not slow down your metabolism and that the fast is truly temporary and the body is not starving. This is why your first meal is called "break-fast" as you break the fast regardless of when you actually eat your first meal. Your wife is partially correct - part of what she is running on is the stored glucose from whatever food she ate the day/night before and the deficit will be made up with fat. She will then "re-fuel" when she eats her next meal on the next day. If, however, your wife eats a typical American diet, then the calories she is eating are nutritionally deficient and loaded with simple sugars. In her case, this will have the opposite effect in that she will burn thru her glucose stores faster as it is sourced from simple sugars thus spiking blood sugar and causing a spike in insulin. This insulin spike supresses HGH and will reduce the amount of body fat used as fuel and makes the body think it is starving and it will slow the metabolism and store more fat from any unused calories (due to slower metabolism) as fat. This will lead to "sugar crashes" and the desire to eat more quick burning sugar enforcing the desire to continue to eat nutritionally deficient calories and the whole viscious cycle repeats.

Soooooooooooooo, the long and the short of it is you are correct if your wife eats like a typical American but she will be correct if she eats a very healthy nutritious diet.

John

Definitely not a typical American. She started eating better and losing weight when she saw me dropping tonnage :).

Well John gave you a pretty detailed response, but also keep this in mind - I have seen a few Omar Isuf videos where he talks about focuisng on 'weekly calories', not 'daily calories. Basically it means as long as you get the correct number of calories you are aiming for in during the week, then you will move towards your goal (fat loss, muscle gain, maintenance). So if you are aiming for 2000 calories per day, and you eat 1000 calories one day, you might eat 3000 the next day.

Obviously your wife is doing it a bit more extreme than that by not eating at all, but it's the same principle :)