More fat less bonking?

linsen

Get me!

Actually it was 5hrs34......

always_tyred

pbt150 wrote:

Always Tyred wrote:

I don't think the time scales are right - metabolising fat into blood sugar is slow compared to the rate of usage of blood sugar during excersise.

He said, not really knowing at all but making a good fist of faking it.

Erm...not really. You can't convert fat into sugar. Fatty acids get chopped up into 2-carbon units that represent the common intermediate in all aerobic metabolism. Glucose goes through the same intermediate, but you can't make glucose from fat.

The average person has around 100,000 kcal of fat reserves, compared with around 1,000-1,500 kcal glycogen in their muscles/liver. Bonking (as far as I understand) is the severe depletion of body glycogen (sugar) reserves, so realistically is unrelated to fat stores. Your fat stores will never realistically get used up to any significant extent on a single ride, so I'm afraid carrying a few extra pounds doesn't help with endurance.

This is off-expertise for me, but isn't pyruvate 3 carbons?

So what you've said is that there's way more energy in your fat reserves than in your blood stream, they both get broken down via analogous processes (so mine wasn't a bad guess) but that they are nothing to do with each other and therefore your fat resesrves won't help. Which is "erm...not really" making sense to me, given that the metabolic pathways converge.

What I said, more or less, was that the relative rates of those pathways is the key; that you use up blood sugar (from breaking down glycogen) way faster than your body is able to draw energy from fat reserves, such that your fat reserves don't help during excersise to any significant degree. That's correct? Or no?

I'm confused, dot com.

Which reminds me - the other thing I "learned" was that your body preferentially eats its own muscles before using its fat reserves. That's layman's language I guess, but I took it to mean that it is quicker for your body to break down muscle tissue (cell walls comprising polysachharides) than to draw energy from fat reserves.

So, basically, as I understood things, which might right, or erm not quite, the body uses its blood sugar, digests a bit of itself and only when it absolutely has to (in order to recover from fainting) digests a bit of one's great fat, possibly hairy, behind.

linsen

Hmm - I've read similar

Blinking typical :?

Jen J

Always Tyred wrote:

pbt150 wrote:

Always Tyred wrote:

I don't think the time scales are right - metabolising fat into blood sugar is slow compared to the rate of usage of blood sugar during excersise.

He said, not really knowing at all but making a good fist of faking it.

Erm...not really. You can't convert fat into sugar. Fatty acids get chopped up into 2-carbon units that represent the common intermediate in all aerobic metabolism. Glucose goes through the same intermediate, but you can't make glucose from fat.

The average person has around 100,000 kcal of fat reserves, compared with around 1,000-1,500 kcal glycogen in their muscles/liver. Bonking (as far as I understand) is the severe depletion of body glycogen (sugar) reserves, so realistically is unrelated to fat stores. Your fat stores will never realistically get used up to any significant extent on a single ride, so I'm afraid carrying a few extra pounds doesn't help with endurance.

This is off-expertise for me, but isn't pyruvate 3 carbons?

So what you've said is that there's way more energy in your fat reserves than in your blood stream, they both get broken down via analogous processes (so mine wasn't a bad guess) but that they are nothing to do with each other and therefore your fat resesrves won't help. Which is "erm...not really" making sense to me, given that the metabolic pathways converge.

What I said, more or less, was that the relative rates of those pathways is the key; that you use up blood sugar (from breaking down glycogen) way faster than your body is able to draw energy from fat reserves, such that your fat reserves don't help during excersise to any significant degree. That's correct? Or no?

I'm confused, dot com.

Which reminds me - the other thing I "learned" was that your body preferentially eats its own muscles before using its fat reserves. That's layman's language I guess, but I took it to mean that it is quicker for your body to break down muscle tissue (cell walls comprising polysachharides) than to draw energy from fat reserves.

So, basically, as I understood things, which might right, or erm not quite, the body uses its blood sugar, digests a bit of itself and only when it absolutely has to (in order to recover from fainting) digests a bit of one's great fat, possibly hairy, behind.

*You're* confused.com? :?

always_tyred

linsen wrote:

Well, actually I have never hit the wall, and I have power walked a marathon in 5 and a half hours (though never run one)
I read an article somewhere about how women and men access energy stores differently, concluding in fact that for women at least , not only "no biking no biscuit" but also "biking no biscuit".
I get by on bananas and SiS too, and when I toured the Isle of Wight I had some nuts.

This has stayed alarmingly on topic - well done guys!

You have to try it at least once, preferably on a cold wet day. Bonking is completely unmistakable and, if you detatch, really quite interesting. Initially, you just feel tired and a given effort is less effective, then, very suddently, you actually can't even seem to try hard, its like there is a disconnection between your muscles and your brain.

If you do it on a cold day, because you can't keep your heart rate up, you can simultaneously get mild hypothermia. Ideally, you could get a puncture as well and be thoroughly unable to use any of your tools to fix it because you have lost all manual dexterity.

Try it Linsen. Honestly, you'll be glad you did.

Fortunately, if you don't die overnight, your fat reserves will possibly provide you will a little help recovery.

linsen

ooh so tempting
:shock:

DavidBelcher

Always Tyred wrote:

This is off-expertise for me, but isn't pyruvate 3 carbons?

(Checks handily-located chemical catalogue)....yup, 3 carbons according to listing for pyruvic acid.

Always Tyred wrote:

I'm confused, dot com.

I was never confused!

David

always_tyred

DavidBelcher wrote:

Always Tyred wrote:

This is off-expertise for me, but isn't pyruvate 3 carbons?

(Checks handily-located chemical catalogue)....yup, 3 carbons according to listing for pyruvic acid.

Always Tyred wrote:

I'm confused, dot com.

I was never confused!

David

Well, I used Wikipedia - I figure that half the stuff on there is posted by bored PhD's and post docs, and thereafter converted back into lectures by stressed young academics who've been assigned lecture courses on subjects they know nothing about.

The question is, though, is pyruvate the intermediate in question? I slept through most of my organic and didn't bother too much with anything beggining in "bio". For financially suicidal reasons, I took an unhealthy interest in rocks with holes in them.

lost_in_thought

My brain just bonked reading that.... :shock:

Layman's terms please! As I keep telling insurance brokers, if you can't explain it to your grandmother, you don't understand it!

always_tyred

lost_in_thought wrote:

My brain just bonked reading that.... :shock:

Layman's terms please! As I keep telling insurance brokers, if you can't explain it to your grandmother, you don't understand it!

I use the "pub landlord" test myself. But that's probably out of date.... or out of business.

Okay, I'm going to do a hilarious impression.......

....can't you READ? I already put it in layman's terms earlier in the thread if you could be bothered to refer to it.

..... okay, who was I pretending to be?

always_tyred

Always Tyred wrote:

lost_in_thought wrote:

My brain just bonked reading that.... :shock:

Layman's terms please! As I keep telling insurance brokers, if you can't explain it to your grandmother, you don't understand it!

I use the "pub landlord" test myself. But that's probably out of date.... or out of business.

Okay, I'm going to do a hilarious impression.......

....can't you READ? I already put it in layman's terms earlier in the thread if you could be bothered to refer to it.

..... okay, who was I pretending to be?

(This is supposed to be a joke by the way LiT )

il_principe

First time I ever bonked was awful, i swear I started hallucinating about baguettes. Baguettes stuffed with salami, tomato and melted Gruyère

mmmmmmmmmmmm Gruyère...

Dammit, just realised that I've left my lunch at home - it was my Thai green curry as well. DAMMIT!

lost_in_thought

Always Tyred wrote:

Always Tyred wrote:

lost_in_thought wrote:

My brain just bonked reading that.... :shock:

Layman's terms please! As I keep telling insurance brokers, if you can't explain it to your grandmother, you don't understand it!

I use the "pub landlord" test myself. But that's probably out of date.... or out of business.

Okay, I'm going to do a hilarious impression.......

....can't you READ? I already put it in layman's terms earlier in the thread if you could be bothered to refer to it.

..... okay, who was I pretending to be?

(This is supposed to be a joke by the way LiT )

It's ok... I was working.... not sulking!

And I can hazard a guess at who you're being...

always_tyred

Working? There's no need to show off.

lost_in_thought

jashburnham wrote:

First time I ever bonked was awful, i swear I started hallucinating about baguettes. Baguettes stuffed with salami, tomato and melted Gruyère

mmmmmmmmmmmm Gruyère...

Dammit, just realised that I've left my lunch at home - it was my Thai green curry as well. DAMMIT!

I'm sure you could make it home to get your lunch - it's only a couple of miles, isn't it?

il_principe

No no no, Gieves are having a sample sale today, suits from £95! - so I'm getting over there at lunchtime.

lost_in_thought

Ahhhh, suit vs. curry, suit wins. Fair enough.

DonDaddyD

What do you mean by bonking?

always_tyred

DonDaddyD wrote:

What do you mean by bonking?

Equivalent of hitting the wall for runners.

Running out of fuel, basically.

pbt150

Always Tyred wrote:

DavidBelcher wrote:

Always Tyred wrote:

This is off-expertise for me, but isn't pyruvate 3 carbons?

(Checks handily-located chemical catalogue)....yup, 3 carbons according to listing for pyruvic acid.

Always Tyred wrote:

I'm confused, dot com.

I was never confused!

David

Well, I used Wikipedia - I figure that half the stuff on there is posted by bored PhD's and post docs, and thereafter converted back into lectures by stressed young academics who've been assigned lecture courses on subjects they know nothing about.

The question is, though, is pyruvate the intermediate in question? I slept through most of my organic and didn't bother too much with anything beggining in "bio". For financially suicidal reasons, I took an unhealthy interest in rocks with holes in them.

From a bored PhD....
Pyruvate is a 3-C compound, and it is ONE of the intermediates in breaking down glucose. It can be metabolised into either lactate (anaerobic) or acetate (2-C), in the shape of the Acetyl-CoA (aerobic). Fatty acids are long (14+) chains of carbons, and they get chopped up in 2-C lumps, again in the shape of Acetyl-CoA. In certain types of tissue this is reversible, so that if you break glucose down into Acetyl-CoA, you can store is as fat. However, the reaction to convert pyruvate into Acetyl-CoA is irreversible, so once it's fat you can only access it by burning it aerobically.

There are of course other factors to consider, such as using amino acids from proteins as fuel, but long story short you can convert glucose into fat, but not the other way round.

always_tyred

Okay, so if you have the time, which as a PhD student I know for a fact that you do, to the extent that the working environement will be a shock to the system from which you will never recover.... what about the relative rates fo the various processes thing?

(Oh, and my extensive Wikipedia reading suggested that the fatty acids also break down to puruvate... it was probably a buddy down the hall who posted the article so you should have a word and tell him he's wrong!)

rhext

Time for a quick experiment I think. Millionaires shortbread. Yum!!

That's loaded with fat, so if I don't bonk on the way home, I'll know the answer.

pbt150

Fatty acids break down to Acetyl-CoA, but can also be made into other ketones in the liver during prolonged starvation to help the brain survive in the absence of glucose. They don't go to pyruvate, this is important. (And I'm looking at big poster of metabolic pathways on the wall in the office as I write.)

Whilst 1g of fat contains about twice the energy as 1g of glucose, it also requires a lot more oxygen to burn it, because it is stored in a less oxidised form - carbohydrate is CH2O, fat is plain old CH2 (give or take).

I have no idea about the maximum rate of lipid mobilisation from adipose tissue, but I would imagine it is quite low as fatty acids aren't very soluble in water, even once you take into account the various mechanisms that the body uses to help this. Muscles do contain fat droplets though, so it's not entirely limited by transport.

However, in response to the OP, having lots of fat vs little fat, the amount of energy the average person (even the average skinny person) has stored as fat means that there's no real advantage from an endurance standpoint of carrying these extra reserves unless you're planning on cycling round the world, slowly.

DavidBelcher

rhext wrote:

Time for a quick experiment I think. Millionaires shortbread. Yum!!

That's loaded with fat, so if I don't bonk on the way home, I'll know the answer.

As it's millionaires' shortbread, would that be your final answer? Or do you want to phone a friend?

Or shall I just get me coat?

David

woodyonthebeach

That sound a bit like an invite in disguise. Kind of like "grab your coat youve pulled" thats sort of thing

il_principe

pbt150 wrote:

Fatty acids break down to Acetyl-CoA, but can also be made into other ketones in the liver during prolonged starvation to help the brain survive in the absence of glucose. They don't go to pyruvate, this is important. (And I'm looking at big poster of metabolic pathways on the wall in the office as I write.)

Whilst 1g of fat contains about twice the energy as 1g of glucose, it also requires a lot more oxygen to burn it, because it is stored in a less oxidised form - carbohydrate is CH2O, fat is plain old CH2 (give or take).

I have no idea about the maximum rate of lipid mobilisation from adipose tissue, but I would imagine it is quite low as fatty acids aren't very soluble in water, even once you take into account the various mechanisms that the body uses to help this. Muscles do contain fat droplets though, so it's not entirely limited by transport.

However, in response to the OP, having lots of fat vs little fat, the amount of energy the average person (even the average skinny person) has stored as fat means that there's no real advantage from an endurance standpoint of carrying these extra reserves unless you're planning on cycling round the world, slowly.

Plus the added weight of extra fat is going to be less than helpful.

Coriander

jashburnham wrote:

No no no, Gieves are having a sample sale today, suits from £95! - so I'm getting over there at lunchtime.

So, did you purr-chase?

always_tyred

jashburnham wrote:

pbt150 wrote:

Fatty acids break down to Acetyl-CoA, but can also be made into other ketones in the liver during prolonged starvation to help the brain survive in the absence of glucose. They don't go to pyruvate, this is important. (And I'm looking at big poster of metabolic pathways on the wall in the office as I write.)

Whilst 1g of fat contains about twice the energy as 1g of glucose, it also requires a lot more oxygen to burn it, because it is stored in a less oxidised form - carbohydrate is CH2O, fat is plain old CH2 (give or take).

I have no idea about the maximum rate of lipid mobilisation from adipose tissue, but I would imagine it is quite low as fatty acids aren't very soluble in water, even once you take into account the various mechanisms that the body uses to help this. Muscles do contain fat droplets though, so it's not entirely limited by transport.

However, in response to the OP, having lots of fat vs little fat, the amount of energy the average person (even the average skinny person) has stored as fat means that there's no real advantage from an endurance standpoint of carrying these extra reserves unless you're planning on cycling round the world, slowly.

Plus the added weight of extra fat is going to be less than helpful.

It aids buoyancy though.

il_principe

Coriander wrote:

jashburnham wrote:

No no no, Gieves are having a sample sale today, suits from £95! - so I'm getting over there at lunchtime.

So, did you purr-chase?

Nope. I've seen women go mad in a sale, but never men. There was something mildly disconcerting about watching a room full of suited men practically fight each other over a pile of clothes! Some great bargains - suits for £45 reduced from £500 but none that I really liked, I can see why a lot hadn't been sold at cost. In retrospect I should have bought £500 worth an stuck it on ebay.

enjoyed the story an assistant told me though, apparently a bloke walked in at 10am:
Customer: "Do you have anything in 46 regular?"
Assistant: "Yes sir, what would you like"
Customer: "I'll take the lot!"

And he did apparently. A truely male approach to shopping!

woodyonthebeach

or something for the fish to feed on. ;-)