How easy is it to build a machine to remove sugar or fat from the blood? If you hook an obese individual to such a machine, do they lose fat? Is this an effective way to lose weight?
If calories are removed, I would imagine the body would tap fat stores to compensate.
Not really dialysis, and I have no precise answer, but I read a memoir by a woman who had some sort of auto-immune disease that required that her plasma be filtered out and replaced fairly often, something like twice a week. Once, she happened to eat french fries right before her treatment, and then she and the nurses noticed that the bag of removed plasma was all cloudy with the fat that had just been removed from her bloodstream. After that, she always ate a big serving of fries during her treatment.
Interesting question and, unfortunately, I don’t have an answer. But, remember, the liver can store a large amount of glycogen that is converted to sugar in the event of low blood sugar. Of course fat is also stored in adipose tissue. So, simply removing sugar or fat from blood ain’t gonna solve your problem.
Also, even if a technique like this were available you still don’t get around the real problem that will resurface as soon as you disconnect the patient…hunger.
If the dialysis or filtering is done while the patient is asleep, unconscious or sedated, they won’t feel any hunger. You could also filter away any toxins released from the fat stores.
Although dialysis has risks, so does lapband or gastric bypass surgery. Liposuction also has risks.
If the patient gets hungry, they can decide to eat. And perhaps become a repeat customer for the clinic.
You are missing my point. First, I don’t know too much about dialysis but I assume it is not as simple as you make it seem. Second, in order to deplete a person of carbohydrates alone you would need to filter continuously for around three days. As you drop blood sugar levels by dialysis (assuming that is possible) glycogen stores from the liver will be mobilized. Most people have about 3 days worth of glycogen reserves (IIRC).
Now you get started on the fat. Depending on the level of obesity I would guess you would need to filter continuously for weeks or even longer. During that time the person will need some energy source to feed the body. Sooner or later protein (i.e. muscle) is broken down and utilized as a fuel. Now, the breakdown product of proteins may also be filtered away during this continuous dialysis.
Assuming all this were to work and you wake up many weeks later completely slim you are going to have one hell of an appetite. My guess is that apetite is what got this patient here in the first place. The body doesn’t just adapt that quickly to being a different weight. Your body will start trying to put that weight back on in short order.
I don’t get this. My hunger comes from my stomach. Full stop. That’s what hunger feels like: a tummy that is not full. That’s why barriatric procedures work.
Sure, the person will be just as hungry as they were before unless the size of the stomach is reduced, but why would they be more hungry? Are you asserting that a fat person digests food more quickly? Or are you using “hunger” to mean that weak feeling you get when you don’t eat for a while?
I should have used the word appetite instead of hunger…although there is more to hunger than just an empty stomach. That is why bariatric procedures can fail.
I do not believe your hunger comes from your stomach. Your hunger comes from your brain. The input from your stomach is only a small factor into how your brain decides if you should feel hungry or not. Sugar levels, hormone levels, etc. all play a bigger role (sorry no cite at the moment).
If you deplete the persons reserves through some sort of dialysis they will more likely than not get more hungry soon afterwards than they normally would.
Theoretically, yes for sugar. In fact, that’s why the dialysis solution is not just saline, but has added dextrose - so it can’t remove too much sugar from the blood.
Dialysis works on the principles of diffusion - movement of solutes through a semi-permeable membrane - and osmosis - movement of water through a semi-permeable membrane. Remember from high school chemistry class that solutes move from an area of higher concentration to an area of lower concentration.
So in dialysis, your blood is on one side of a semi-permeable membrane and the dialysis solution is on the other. That membrane is your own peritoneum for peritoneal dialysis or synthetic for hemodialysis - those look like fiberoptic cables in a tube. The dialysis solution is low in those solutes we want to get out of the blood, like creatinine, phosphorus, and urea. The blood is high in those solutes (abnormally high, because the kidney isn’t filtering them out properly). So the solutes move from the blood, through the membrane and into the dialysis solution.
If a person has excess potassium or calcium in the blood, then the dialysis solution is low in those, so they diffuse similarly. If the person does not have excess potassium or calcium in the blood, we add those to the dialysis solution in the same proportion as they are in the blood so they don’t diffuse.
Sometimes people on dialysis need more bicarbonate in their blood, so we add it to the dialysis solution, and it will diffuse into the blood.
I told you all that so I could tell you this:
Sugar is a solute in the blood. If you have too much of it in your blood, then yes, dialysis will remove it. HOWEVER, it’s a crappy way to do it unless you have no other choice. It runs a huge risk of us taking out too much sugar too quickly for your body to adjust, causing low blood sugar (hypoglycemia) which if unchecked will lead to seizures, coma and death. So we add sugar (dextrose) to the dialysis solution in about the same or slightly higher concentration that it should be found in the blood. If you have more sugar than that in your blood, it will indeed diffuse out of the blood into the solution. If you have less sugar than that in your blood, it will diffuse out of the dialysis solution into the blood. Remember - it always goes from where there’s more to where there’s less.
So if we ran a dialysis machine with no sugar in the dialysis solution, then yes, it would pull sugar out of your blood. In the short term, this will make you very, very hungry. Then it will make you cranky, sleepy and give you a pounding headache. If we keep going, you’ll die. It would pull out of you at a much faster rate than your liver can release glycogen stores as glucose to compensate.
In other words, we’ve just put you into a hypoglycemic state, the same state diabetics are in if they don’t eat and/or exercise too much and/or take too much insulin. Remember Shelby from Steel Magnolias, when her mom had to force her to drink the orange juice? That’s what we’re talking about here. Not fun. Not a good weight loss strategy.
I believe that fat molecules are too large to pass through the dialysis membrane, but I’m not certain of that. I know that fat-soluble *vitamins *will not be removed by dialysis, which is why people on dialysis should not take fat-soluble vitamin supplements.
So give the patient glucagon to prevent the hypoglycemic state and use a smarter, non-zero mix of sugar in the dialysis solution if that works better with the body. What if we use a computer monitored and adjusted dynamically controlled low-sugar mix?
Or could we maybe add some hormones to enhance the release of fatty acids from adipose tissue and filter those out as well?
Assuming you don’t have diabetes, the amount of sugar in your blood IS perfect, or as close as we can get.
But sure, you could perhaps (again, theoretically, with better instantaneous blood sugar monitoring and antihypoglycemic medications than we have now) try to keep a person’s blood sugar just *slightly *low by using a lower percentage of dextrose in the dialysate. Then they’d only have the extreme hunger, headaches and crankiness to deal with.
And the hours and hours that this would take and preventing the person from stuffing their faces full of cheeseburgers and milkshakes between treatments because their body is telling them they’re starving to death.
Then you have to consider the surgery to put in the AV shunt (the place in the arm where they surgically attach a vein to an artery to make a big swooshy spot of blood vessel to put the dialysis needles into), circulation loss to the extremity distal to the spot and prevention of infection and collapse of the fistula.
If the patient already needed dialysis, there’s no additional risk factor.
But now that I’m thinking of it, if you’re going to surgically implant a shunt, why not implant an entire miniaturized dialysis machine inside the body? It would have a little door that you could open to empty out the stuff that got filtered out.
And you could filter out a lot of garbage - calories, salt, toxins, etc.
As for headaches and crankiness, the machine could run when you are unconscious, for example, many people spend a good portion of their day asleep.
I’m sorry, but this is making less and less sense.
If it was easy to implant a miniaturized dialysis machine, they would be implanting them all the time in people who actually need it because, you know, their kidneys don’t work. They are currently working on some prototypes, but they are far from a clinically useful model.
Filter out toxins? Outside of pseudoscience, your body does a fine job of filtering out toxins on its own. And salt? It’s not like your body has some huge reservoir of salt waiting to be filtered out. Your sodium levels are adjusted by precise homeostatic mechanisms, and removing too much salt will kill you. If you are kind of puffy because you’ve eaten too much salt which in turns causes you to retain water, wait a day or two and don’t eat much salt and you’ll be fine.
The machine filters out some glucose, but no more than your glucagon can mobilize on its own, because otherwise you’ll die. So why not just sleep, not eat any sugars or other calories while sleeping, let your body use up that sugar while performing its ordinary metabolic tasks and leave out the dialysis machine?
Yeah, this is a poor method to lose weight, for reasons that others have stated above.
Assuming the goal is weight loss in obese individuals, keep in mind that the hardest part isn’t necessarily the initial weight loss, but rather maintaining new habits and keeping calorie consumption low (in the fact of metabolic structures which will probably try their hardest to keep weight on).
And blood sugar levels really do have to be tightly regulated. Also, you’d have to be on constant dialysis for this to work, because it does not take long for excess ingested sugar to be stored as fat.
There are just a few problems here . . . but one that should be pointed out is that fat molecules (i.e. free fatty acids) are way too large to pass through a dialysis membrane efficiently. So, dialysis ain’t gonna work for fat removal.
In terms of glucose, in theory the idea works. But, as others have said, it’s not a trivial matter to keep the blood glucose in a safe range while simultaneously removing it from the bloodstream with dialysis. You’d probably wind up having to infuse as much “rescue” glucose as you were removing in order to counter the hypoglycemia which you can bet would occur, and probably very often.
A nitpick from upthread: we have not much more than 12 hours of stored glycogen in the liver. Certainly not three days worth. And, once the glycogen is depleted (and it would get depleted since it would be broken down into glucose in order to offset the glucose being removed by dialysis), glucagon won’t do a thing, i.e. in the short term glucagon raises the glucose level primarily by causing glycogen breakdown. If there’s no glycogen to break down, glucagon won’t make a difference (and that is why, by the way, for those of you who know about such things, glucagon is ineffective for the treatment of the hypoglycemia that can occur as a result of heavy alcohol use in someone who also hasn’t been eating much, i.e. in alcoholic ketoacidosis, a condition characterized by hypoglycemia and ketoacidosis - in this condition, because the patients haven’t been eating, there is no glycogen in the liver on which any administered glucagon could act).
OOOOOoooooooohhhh…That makes so much more sense than when my teacher tried to explain it…Thanks! 