Diabetes : what happens with ALL carbs after eating and during exercise?

[ChrisM]

I am trying to understand what exactly happens with all sugars, fats and carbs after eating and during exercise.

A I understand it, after eating ALL sugars, fats and carbs are broken down into GLUCOSE which is then transported around the body for cells to absorb, and this glucose is absorbed only if insulin is present. Glucose that is not absorbed is then stored first in the liver as glycogen then as fat in the abdomen etc.

During exercise the glucose stored in muscle cells is used first, then when that is used up the glycogen in the liver is transformed into glucose, then when that is used up fat is transformed into glucose.

But if glucose and only glucose is the form of sugar that cells absorb and insulin is required for this then does exercise encourage production of insulin or does adrenalin make absorption of glucose easier with smaller quantities of insulin?

Do muscle cells require insulin for absorption of glucose? Or do they absorb other forms of sugar for energy, whether exercising or not?

 

[Robster65]

Wow. Good question.

I think. Carbs release glucose into the bloodstream. Fat stays as fat. Protein stays as protein. BUT.

If you're asleep. Carbs will be used as energy via insulin to the cells, with the rest transformed to fat by the liver. Fats will be laid down as body fat by the liver or transformed to repair cells, etc. Not sure about the protein other than being used to repair cells.

If you're exercising, carbs as glucose will be used as fuel in a greater quantity. Muscles have more insulin receptors than fat or other cells. Fat can be transformed to carb by the liver when needed. As can protein once the fat runs low.

The brain and nerves can absorb glucose without insulin. Hence neuropathy when you run high, because it passes the cell wall unregulated. The brain can also run on ketones I think but for other cells it's poisonous.

All other cells require insulin to absorb glucose for fuel. WHen exercising, you're metabolic rate increases, so you burn glucose at a higher rate and build muscle which will give you more insulin receptors for future. Hence the reduced resistance if you regularly exercise.

I think.

Rob

 

[Northerner]

...But if glucose and only glucose is the form of sugar that cells absorb and insulin is required for this then does exercise encourage production of insulin or does adrenalin make absorption of glucose easier with smaller quantities of insulin?

Do muscle cells require insulin for absorption of glucose? Or do they absorb other forms of sugar for energy, whether exercising or not?

The body's cells become more sensitive to insulin with regular exercise, so less insulin is needed to provide the transport of glucose into the cells - the opposite of insulin resistance where there are few or damaged receptors on the cells so more insulin is produced to try and overcome the lack of receptors. As an illustration, when I am running regularly I need to reduce my insulin by up to 50% - so I'm using less rather than more and if your pancreas is supplying the insulin the result must be similar 🙂

I believe there is also another mechanism at play when muscles work which does not require insulin to transport energy, but I'd have to dig around to find out what it is called.

 

[Ellie Jones]

Fat and Protein can be an energy sources, About 50 something percent of protein will breakdown into glucose but it's a pretty slow rate..

Carbs are the easiest form of fuel the body can use to convert to energy, but it can also use Fat which is called ketogenic diet but this is a much slower process..

The problem with T1 diabetics, is that when the insulin isn't being produced then the body will look for fat, but unlike a normal Ketogenci diet which takes fats from the body main store, The lack of insulin means that it will start stripping the fat from muscle's causing dangerous ketones and muscle wastage etc..

Google kentogenic diets for more detail information

 

[trophywench]

... my understanding is c 50% of Protein as Ellie says, and c 10% of Fat. But as the body has to work harder to use Protein and Fat as a glucose source it will always ignore both in favour of available carbs FIRST, cos the conversion process is less hard work. (and I spose it must need glucose to convert the food anyway whatever form it takes? dunno)

 

[Robster65]

The last dietician I saw said that protein conversion (gluconeogenesis) won't happen unless you're on low/no carbs. Fat is obviously converted with exercise hence weight loss.

It's flippin complicated.😱

Rob

 

[Ellie Jones]

The HCP's do tend to ignore protein and it's impact on blood glucose with the assumption that because of the time it takes the body to process it into glucose, activity levels avoid it from impacting on the blood glucose levels..

A 3 egg cheese omelet is enough to require insulin to counter react the impact on my BG... Cheese and Cream crackers requires an addition of insulin to cover the cheese..

Now the main problem and why our HCP's try to make us believe that we don't need to include insulin for protein is more down to injecting the extra insulin to cover it..

As yes you do need the insulin, but because of the differential of adsorption time between the insulin and protein the insulin tends to cause an hypo! So it would require a split bolus injection to cover probably.. Which they do like to ignore this makes life easier for the diabetic.. Less injection and maths!

 

[HelenM]

Starch and sugars are converted to glucose in the digestive tract. Glucose and other simple sugars (fructose, lactose) are transported to the bloodstream to be distributed by the liver.

According to Jecquier (1995)http://journals.cambridge.org/downl...43a.pdf&code=53ee6472c537110fe332fec41a70bb64

In a normal healthy male:
Out of a 100g glucose ingested:
40g oxidised (ie burnt and used for immediate fuel,
50g stored as glycogen
10g is not absorbed during the the first 3 hours.
The body can normally store between 250 and 500g of glycogen. It is only after these depots are full that excess carbs are converted and stored as fat.
Fats:
Fats are transported from the intestine in the lymphatic system and then in the veins in packages called chylomicrons ie lipoprotein particles including triglycerides and cholesterol
It is stored in triglyceride form in fat tissue. Fat tissue isn't just a place where excess fat is stored. Fats are constantly being stored and released and used for energy. (cyclical)
After a meal higher insulin levels may surpress this breakdown of fats for use; but never entirely. Triglycerides can be broken down into glycerol and fatty acids. The former can be used to make fuel in the liver. The latter can be used as fuel. (we all burn both fats and glucose)
see http://science.howstuffworks.com/environmental/life/human-biology/fat-cell1.htm

Proteins
are broken down in the stomach, synthesised into various amino acids transported to, then distributed by the liver and utilised for building all cells in the body.
Some of these amino acids can also be used, if needed for energy. They are converted by gluconeogenesis to glucose.
This occurs mainly in the liver. Excess protein can be coverted and stored as fat.

Muscle protein can be broken down to be used to make fuel (this happens in starvation,(including 'crash' dieting) or when there is insufficient insulin so the cells think they are starving


I've left a lot out, hope I haven't got anything terribly wrong. Its really complicated and the more you look it up, the more complicated it seems to get.

Exercise gets even more complicated, I'll leave it to the real experts.🙂
The graph at the bottom of this page shows how in endurance exercise,after the intial burst, fuel is mostly fatty acids and some glycogen from muscle cells but the capacity to continue is governed by capacity of the liver to keep sufficient glucose in the blood . (hitting the wall is basically a hypo)
http://www.medbio.info/Horn/Time 6/muscle_metabolism.htm
This is a succinct but quite complex account of fuel use in exercise.
http://www.runsweet.com/BodyResponse.html

 

[Northerner]

Thanks Helen, really useful to know. The Diabetic Athlete's Handbook explains quite a lot too, must go and dig out my copy and refresh my knowledge! 🙂

 

[Bolddog]

I wish I could 'vote for this thread'

Explains in a minute what I have suspected from endless trial & error and also much much more

Many thanks to you all, ( esp ChrisM & HelenM... no relation ? )

If diabetessupport did stickies, wouldnt this thread be one ?

Ruff Ruff

Bolddog

 

[Robster65]

Thanks Helen, really useful to know. The Diabetic Athlete's Handbook explains quite a lot too, must go and dig out my copy and refresh my knowledge! 🙂

There's a lot about ATP but you need a good run to destress after reading about it !

Rob

 

[HelenM]

There's a lot about ATP but you need a good run to destress after reading about it !

Rob

Try reading the wiki article about ATP .
( To me its a bit like trying to read in a different language. Every now and then theres a bit I understand but most of it is beyond me)

 

[Copepod]

Wiki articles aren't always written to assist lay people to understand science! Mind you, I decided not to pursue biochemistry after first year at university, and only returned to it some 20 years later in a genetics higher education course, when things did come back to me, apparently easier than to others with no biochemistry knowledge.

HelenM has already mentioned Runsweet - http://www.runsweet.com/DiabetesAndSport.html is a good page to start, as well as the specifics in the page HelenM mentioned. What I like about the website is that it has both scientific principles / background, as well as profiles of people in various sports, although still not all eg no orienteering nor mountain marathon pages yet. Perhaps a couple of friends and I should take action, but we're too busy doing things!

 

[Robster65]

I did a quick last night and found several web articles describing metabolism/studies for athletes and how the body utilises carbs or fat when pushed to the limits, but there's not much about for us more sedentary folks.

The implication on one well written article was that, fat or carb are equally efficient fuels for endurance athletes who are aiming for long distance rather than speed. But for marathons and under, where the body is being pushed for speed, carbs give the better performance.

For just pottering, where there is unlikely to be an exhaustion of energy supplies, it seems that pretty much everything will be stored as fat if not burnt off. It also had a lot to say about cholestorol in athletes. It implied that HDL will go up and down according to how much fat is consumed. The higher the HDL after eatign fat, the better the body is able to process saturated fat. But with a low HDL, sat fat is a bad idea full stop.

Amazing how it all evolved to deal with all this rubbish without disturbign us at all. It's only when things go wrong that you start to take notice.

Wow.

Rob

 

[Northerner]

...
The implication on one well written article was that, fat or carb are equally efficient fuels for endurance athletes who are aiming for long distance rather than speed. But for marathons and under, where the body is being pushed for speed, carbs give the better performance....
Rob

I'd put marathons in the endurance class Rob - I've certainly never run them for 'speed' 😱 Actually, it's interesting when it comes to the 'Wall' in a marathon. When I began running marathons in the early 1980s I remember reading the hitting the Wall was the point at which your body has exhausted all its easy-to-process supplies of energy (muscle/liver glycogen) and begins to convert fat which is more onerous on the system. Once the process is established though, it becomes more efficient and this is why you often get your second wind once you are over the Wall. Elite athletes train themselves so that they do not hit the Wall until they are beyond the race distance, so they can continue at an extremely fast pace all the way through. Doesn't always work of course, since sometimes your body simply isn't up to it. However, when you hear people like Brendan Foster talk about people 'seriously slowing' or 'hitting a bad patch' towards the end of a marathon etc., you have to bear in mind that this might mean they are running 20 seconds a mile slower than their usual 4'30" miles, hardly a serious slowdown! 🙂

 

[Robster65]

I think they were aiming the advice at elite runners or serious competitors and did make a distinction between which regime was more suited to those over or under a certain marathon time.

I've found the article...

http://www.pponline.co.uk/encyc/sports-nutrition-should-athletes-use-fat-or-carbohydrate-as-fuel-631

It's lengthy but interestign and may even give you something to try out.🙂

My endurance involves walking for more than a couple of miles at 3 to 4 mph so not quite the elite level yet.

Rob

 

[trophywench]

Rob, if you tell me which pub you are finishing at I'll meet you there in the car and give you a lift back.


"What did you do today Jenny?"

"I went and met Rob, cos he said he was going for a walk. Nice scenery, 3 or 4 miles, very enjoyable."


That's my kind of exercise!

 

[heasandford]

I wish I could 'vote for this thread'

Explains in a minute what I have suspected from endless trial & error and also much much more

Many thanks to you all, ( esp ChrisM & HelenM... no relation ? )

If diabetessupport did stickies, wouldnt this thread be one ?

Ruff Ruff

Bolddog

And another vote from me too! I did a course in biochemistry as part of my Food Science degree a million (or more!) years ago, but when I was diagnosed with diabetes only 11 years ago, I could not find the detailed breakdown of what was going on and my dietician specialists certainly didn't want to tell me! This thread puts it all succinctly - thanks!

 

[HelenM]

I found this post on a forum some time ago from Cassandra Forsythe, one of the researchers in Jeff Voleks lab. I think reminds us that when things are averaged in research projects they mask very clear individual differences.

While working in Volek's lab over the past 5 years and conducting some of the research ................

We had subjects do terribly on ketogenic low-carb, and others do fantastically. But, when you're writing your results, you're stating the average results, and on average, in the study population we researched (while I was in the lab), most responded more favorably to keto low-carb vs low-fat........................

full post (and horrendously long fairly acrimonius thread)
http://www.jpfitness.com/showthread.php?t=39280&page=5

My other thought is that no-one researches about people like me, I'm probably an oddity anyway
I'm slow and take over twice as long as younger 'real' athletes, even real athletes of my own age are much faster. That must make a difference in the fuel requirements even without T1 diabetes into consideration.

 

[Robster65]

Rob, if you tell me which pub you are finishing at I'll meet you there in the car and give you a lift back.


"What did you do today Jenny?"

"I went and met Rob, cos he said he was going for a walk. Nice scenery, 3 or 4 miles, very enjoyable."


That's my kind of exercise!

Sadly, the nearest pub is about 50m+ lower than us and a lot of winding lanes away.
Getting is ok but you then have to climb up a very steep hill to get back.

We're off round the mountain shortly before the wind picks up again. No pubs but 3-4 miles and lovely scenery. If you can get here before about 2pm, I'll hang on for you !

Rob