Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: Reenen on 09/04/2014 11:35:50
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Lets say I ingest 500ml corn syrup every day (and nothing else) and I "output" 500g to toilet every day.
Do I gain weight?
Or put differently... can food let us gain more weight than it actually weighs?
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Ok, I'm seeing about 4 calories per ml for corn syrup, so you would get about 2000 calories from the corn syrup.
And, essentially 100% is absorbed by your body. No fiber and etc that will be excreted, so you may well gain weight.
Now, the question is about ins and outs.
If you ate/drank pure corn syrup, you'd likely decrease your bowel movements significantly as the corn syrup would enter the digestive system, be absorbed, and not pass through.
Are you counting water? Air?
Obviously your body looses a fair amount of water that is hard to track.
Let's consider the metabolism of fructose, C6H12O6 for energy.
C6H12O6 + 12O2 ==> 6CO2 + 6H2O.
Now, calculating the molecular weight:
Fructose: 6*12 + 12*1 + 6*16 = 180
Water: 6*(1*1+16) = 102
So, if you add in the oxygen, and CO2, then your equations are balanced. However, if you ignore the oxygen and CO2, and just consider fructose & water, one does in fact excrete less water than the sugar that was taken in.
Fat production might be converting the sugars into triglycerides. There certainly are many different triglycerides, but consider: C54H96O6.
So we get:
9C6H12O6 ==> C54H96O6 + 6H2O + 21O2
Yes, you may in fact create some oxygen when making the fat.
Again, calculating our ideal ins and outs, ignoring the gases.
Fructose: 9*(6*12 + 12*1 + 6*16) = 1620
Water: 6*(1*1+16) = 102
Anyway, in moles, one may end up with more moles of water than one started with fructose. However, calculating the ideal weight, one excretes less water than fructose taken in.
If you balance the equations using oxygen and CO2, then your ins and outs should be balanced. However, you suggested weight gain, in which case the total input is actually higher than the output.
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Please correct me if I am misunderstanding you (as I am really bad at chemistry), but from what I read from your post is:
In theory if you excreted 500g for every 500g of syrup you'll stay in equilibrium (weightwise), but the fact is that you would not be able to excrete 500g anymore due to the way the body metabolises the syrup. So over time you would gain weight due to this fact (but not a full 500g per bottle as some parts of it is still excreted).
The origin of my question is from people who gain weight and then blames the piece of cake they ate over the weekend. Is this valid? Surely they could not gain 500g of weight by eating a 250g slice of cake?
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This is the easy part of the question
"Or put differently... can food let us gain more weight than it actually weighs?"
No.
If you just ate 500 g a day of corn syrup you would lose a lot of weight.
Most of that would be water.
You would get very dehydrated and it would be very bad for you.
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Personally I don't count calories, but I've been observing my diet for a few years.
Technically one can't eat 1 pound and gain two. But... not all food is created equally.
When I eat pizza, sometimes I find myself just parched. I presume it has a little extra salts that I don't normally get in my diet, and so I end up drinking extra water. So, perhaps one could eat a pound of pizza and gain two pounds.
I have dieted, and when I'm dieting heavily, a single good meal seems to set me back several days as the weight bounces up by a couple of pounds.
Anyway, not all foods are created equal.
These are ballpark estimates from the top of my head, not to be taken as gospel- Simple sugars, glucose, fructose, sucrose, etc... 99% absorbed, very little excreted
- Typical cooking oils... 99% absorbed, very little excreted
- Salts... highly absorbed, and excreted in the urine for fluid balance. However, it could cause at least temporary retention of water
- Simple starches, white flour... 90% absorbed, small amount excreted
- Whole Wheat... 50% absorbed, 50% excreted
- Prunes, Plums.... 30% absorbed, 70% excreted
- Blackberries... 15% absorbed, 85% excreted
- Green Salad.... ???? Watch the dressings
So, eat a pound of white bread or a pound of 100% whole wheat bread, and you'll gain more weight with the white bread.
You're cake may hit you in all the wrong places. Pretty much nothing in it is non-fattening, and most of it will be absorbed by the body.
Lots of white flour
Lots of simple sugars
Lots of oil
Also when thinking about wight, you have to consider your 1000 to 2000 calorie "normal" diet. Anything extra will go to fat. So, that extra piece of cake may not seem like much, but if it is on top of your normal diet, it may all go to fat.
However, keep in mind, a party or celebration may throw off your entire diet.
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Interestingly, body fat is not pure fat, and so an ounce of pure fat contains more calories than an ounce of body fat. So you could gain more than an ounce of body fat as a result of eating an ounce of oil (about 1.14 ounces). But you can't gain mass without eating it, so you'd need to take in extra nutrients to store this ounce of fat as 1.14 ounces of body fat. As BC noted above, you need to take in more than just one concentrated form of calories or you die. The totality of all you take in will always be less than what you gain.
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Obviously you also need water + air to survive, although you can take in some of your liquid requirements as part of your food.
You would probably be safe enough taking in a diet high in sugar plus supplemental vitamins, salt, water, minerals, and electrolytes for a few days. Your body does also need some protein, but should be fine without it for a short period.
Incidentally your body makes acids from protein metabolism. I heard of a medical student who ran an experiment eating a skittles only diet for a few days, I think, and managed to slightly increase their blood pH, if I remember correctly.