Lets say that in the morning I weigh 175 lbs when I step on the scale. I proceed to my car, drive to work, sit in my office all morning and go to a steak house at lunch. I eat a 64 oz steak and go back to work until 5. When I get home I reweigh myself. Technically, I should be at 179 lbs. Would this be true? Over the course of the 5 hours since lunch, how much of that steak has my body broken down…and does that equate to a loss of the original 64 ounces I consumed? I would imagine that the only way I will lose some of those 64 ounces is through exercise or of course a trip to the bathroom.
So how long does it take for the body to break down a meal so it weighs less than when it was consumed?
I can’t answer the question directly, but the other ways you lose mass are through exhalation of carbon dioxide and water vapor, and evaporation of water from your skin. Every one of those carbon atoms comes from your consumption of carbon-based chemicals (carbohydrates, fats and proteins). And a good bit of water comes from the food, as well as your direct consumption of aqueous solutions.
Also, figure that 64oz steak was weighed before cooking, so you didn’t add that much weight to your alimentary canal. And a lot of that weight was water.
I imagine a full theoretical calculation is complicated, though I don’t doubt that someone has determined the answer empirically.
That mass gets turned into energy for your body and is no longer mass. I don’t know the full calc but as long as your heart is still beating, you are burning away food all of the time.
No. The energy from food comes from chemical reactions, not from the conversion of the atoms in the food into energy. The mass of the food is conserved.
Food is broken down in digestion to component parts, and then used to create chemical energy to run the body.
Not the same as converting mass to energy as in an A-bomb, for the nitpickers out there. This is an important nitpick, though, because in that case there is a loss of mass but in chemical conversion there is no loss of mass.
This energy is used to keep the body at, well, body temperature, and so is eventually emitted as heat to the surrounding atmosphere. Exercise is nothing but a means for emitting heat faster compared to a resting state.
Even without excretion of undigested food and urine, therefore, a number of pathways exist by which digestion leads to weight loss from the body.
I’m not a chemist, but I’ve had chemistry. Isn’t there mass associated with the energy of the chemical bonds digestion breaks down? Isn’t that in fact the reason we can get energy from food? By converting that mass into energy?