How long does it take excess calories to turn into fat?

I’m talking the chemical process. I know that if a person were to overeat on day one, the weight gain they are seeing on day two isn’t actual FAT, it’s the volume of food still in their body. It may eventually turn into fat, but how long does that chemical process take?

Based on everything I have read: a couple of days, maybe several.

It depends on the speed of your digestion, what you ate and your overall activity level.

If you cram down 2500 calories today, and you digest them all perfectly, and you burn 2000 of them, the 500 are held up as reserves in various forms for a day. Maybe a little less… maybe a little more.

I am cramming together everything learned over many years. Generally, daily weigh-ins are up against far too many variables (main one being food in the digestive system, but there are others). If you extend the weigh-ins to 3 days apart, they get more reliable. This is some form of evidence to me that speaks to the issue at hand.

It seems to me that you have to go about three days to get some degree of consistency. It seems to be enough time to allow for full digestion, absorption and eventual fat storage.

I think Philster’s on the right track. I would just throw out some other numbers and observations.

Food only stays in your digestive tract for about 24 hours. So anything that your body can’t extract into the bloodstream in a day is going to be unavailable for further digestion.

The bloodstream has a pretty low tolerance for excess calories. Diabetics can go into a coma by having just five or six times the normal blood glucose, and diabetics who have way too little blood glucose are obvious by the smell of their breath due to ketones. Too high a concentration of ketones results in acidosis which is also potentially fatal. I don’t know numbers in terms of calories, but it’s safe to say that your bloodstream is not a way to temporarily store significant calories.

Muscles store glycogen for about an hour’s worth of activity, and the liver has enough for about a day. So an excess of maybe a day’s worth of calories from starch/sugar might hang out as glycogen there. (And even that would assume you were practically fasting for the day before).

So, I’d say that 2 days is absolutely the upper limit. Anything longer and you’ve either excreted it or died from it.

I have read that fat storage can actually be completed overnight, but I don’t have a cite for that.

Wow, interesting, I thought it took much longer then that! Thanks.

I always do this kind of math when Girl Scout cookies come out.