Calories and metabolism/digestion.

When a box says “100 calories per serving” that is the MAXIMUM cals from a serving of the food right? So…

If food goes through you fast, say you poop 4 times a day or something, do you absorb less calories than the person who poops once a day? Since the food is not in your system processing as long?

Does a persons metabolism effect how many calories they absorb from the food?

Good question, I was wondering about this the other day.

Calories are measured in a bomb calorimeter, and it does combust the food completely, while your digestive system will not. Notably fiber is measured as having 4 calories per gram in a calorimeter, but since it passes undigested does not add significantly to the calories absorbed by your body.

Other food may not be fully absorbed depending on how well the food is chewed and digested, but in general other than fiber there is very little “pass through” of undigested nutrients. I suppose swallowing whole nuts or seeds could decrease absorption significantly, especially if they were a major part of your diet.

So since I poop 3-4 times a day I’m probably not absorbing as many cals as someone who poops once a day?

Unless you have an actual intestinal disease, the number of times you poop is entirely unrelated to the calories you absorb.

What **Bill Door ** said is correct. Virtually every recoverable calorie is absorbed by your system before it reaches the colon. The only exceptions are fibers and lactose, for those people who are lactose intolerant. And lactose would be a negligible percentage of calories. Fiber is not counted in the calorie information on any packaged food in the U.S. precisely because it is not absorbed.

The human body is extremely efficient in breaking down foods to digestible pieces. Diarrhea is normally a problem because of dehydration, not the removal of usable food. Almost no condition except for a few pathological ones will do this.

Everything you eat goes into making nice healthy fat. OK, a bit of it goes to muscle or energy and suchlike. The number of times you excrete is meaningless. Normal evacuation is defined as anywhere from three times a week to three times a day, it’s that variable.