That’s because you’re eating a load a processed junk – far too many carbs, nowhere near enough protein, not enough fat and very poor micronutrient density.

It’s how I’ve always fuelled rides, although granted if I had had more pocket space I’d have taken a banana or two as well. I’ll confess I’ve never understood the role of protein and fat DURING activity, I can’t believe the double bacon and egg rolls I see other riders scoffing at coffee stops!

I don’t know how Z2 changes nutrition but I’m not sure lack of micronutrients, protein OR fat is an issue over three hours after a full and relatively health lunch?

That’s because you’re eating a load a processed junk – far too many carbs, nowhere near enough protein, not enough fat and very poor micronutrient density.

I don’t think eating protein and fat on the bike will help.

I would suggest not eating that shite on the bike though for a steady 75km I would look at a banana, couple of bottles with a dilute carb mix in, I think carbs in a bottle are taken in regularly and you don’t get spikes and then crashes in blood sugar like you do with sugary snacks. I imagine that is why you feel so hungry after.

I was fuelling all my Z2 work with carbs last year and got fat on it! Since Oct, I’ve switched to just squash and managed a bit of concurrent weight loss.

I don’t really feel hungry on Z2, after about an hour there is a definite switch though. I feel like I’ve finally engaged fat burning mode! Then I don’t feel like I need to fuel at all. I’m keen to try a fasted century when the weather perks up, just to see how fat adapted I really am 🤣

I eat normally the rest of the time. Definitely going into them with onboard glycogen stores topped off.

I’m doing 120min Erg sessions on the trainer at 235w now. Right in the middle of Z2 HR 😎 Only a couple a week though, the rest are lower intensity and or longer.
I went out yesterday and did 49 miles in about 3hrs. The middle 2hrs was the same kind of Z2 HR as the ERG sessions and I arrived back feeling like I could do it again! Then tonight is Z1 with spin ups and then back to the Z2 ERG tomorrow.

In a couple of weeks time, I plan to start my muscular endurance work, so one of those 2h Z2 ERG session will become Tempo! Gonna shoot for 120 mins progressing each week at 250, 260, 270 then recovery week, then 270, 280, 290 then recovery week, then 280, 290 and finally 300.

Those bad boys will probably have a corresponding increase in carbs alongside them 😮‍💨

Z2 is primary fat using. You are using slow twitch fibres which use fat as an energy source. I wouldn’t be carb loading while doing it. You want the fat to get used and increase the numbers of mitochondria in the cells. Carbs will just switch metabolism to glycolysis rather than beta oxidation.

Thats far two much for steady Z2. For reference on Saturday I’ll do 2h:20m with:

1 x slice brown toast with two scrambled eggs with 1 milk & brown sugar coffee
1 x double espresso immediately pre ride
2 x Torq Hydro (30g carbs total) bottles

Post ride – timed to finish at lunchtime to avoid snacks – 1 x SIS Rego (normally Protien only but I’ve a 4h ride the following day), plus a roast chicken salad sandwich, and some crisps*.

*not the best but I like crisps, a lot.

Z2 is primary fat using. You are using slow twitch fibres which use fat as an energy source. I wouldn’t be carb loading while doing it. You want the fat to get used and increase the numbers of mitochondria in the cells. Carbs will just switch metabolism to glycolysis rather than beta oxidation.

So much bollocks in such a small amount of text!!! 😄😄

Well in fairness I guess I had always understood Z2 wasn’t using up Glycogen stores, but I just haven’t figured out the extreme grumpiness and tiredness after fasted or near fasted rides. I’d be doing them all the time otherwise as I seemed able to ride for a good few hours on not much more than a banana and water.

Whereas I can finish a well fuelled ride like above still feeling good on the bike etc. albeit then having a decent appetite.

I can’t touch carb drinks on cold easy rides, I need to stop and pee way too much!

Z2 is primary fat using.

It still uses carbs, depending on who you are though. You will always use some and it can be quite a bit. The key is to find out how little you can get away with cumulatively. I could do 2hrs on no carbs easily, but the next day I’d be hungry and the next day my riding would suffer and I’d feel worse etc, as my glycogen stores were further depleted. I think the trick is to maintain slightly depleted glycogen all the time, but not getting fully depleted otherwise you crash.

Something something glucagon something.

I think carbs in a bottle are taken in regularly and you don’t get spikes and then crashes in blood sugar like you do with sugary snacks.

It works a little differently when you are exercising because your cells are using their glycogen. High GI carbs and the insulin are good in this case because you can replenish what you’ve depleted easily and the insulin is important for that. Insulin is only a problem when you are idle with full glycogen stores because then it promotes lipogenesis, as I understand it.

Yes, you want to be using some fat but you will anyway in Z2. As long as you take small amounts of carbs, enough so that you’re not ravenous when you get home or the next day, you’ll be alright. The harder you ride obvs the more carbs you need to take on.

Yeah, I’ve tried fat adaptation and all that stuff in the past. It basically robbed me of the things I find fun on a bike – riding hard and eating sweeties. I didn’t notice any significant improvement in aerobic abilities or lose any weight. I don’t think I got any satisfaction out of riding for hours on not much food.

I don’t know how Z2 changes nutrition but I’m not sure lack of micronutrients, protein OR fat is an issue over three hours after a full and relatively health lunch?

I laughed at this too. Maybe your ride has made you vitamin B deficient or something!

It works a little differently when you are exercising because your cells are using their glycogen. High GI carbs and the insulin are good in this case because you can replenish what you’ve depleted easily and the insulin is important for that.

It would depend on a host of factors like exercise intensity, genetics (altering the balance of different biochemical pathways for example), prior training over the long term, prior training over the short term. I was just saying what works for me on my lower intensity rides, if the poster found he was hungry at the end of a zone two ride of a few hours having eaten what sounds like quite a lot (for me) I would suggest changing it up a bit…we are all different and blanket statements about one thing or the other or one metabolic pathway or another or one type of muscle fibre or the other distil it all down to worthless bollocks.

@Molgrips when you are exercising above walking pace, you don’t need insulin as the Glute 4 transporters are activated by the muscle contractions. It’s why exercise is so good for T2D- especially right after eating. Even standing up triggers more Glute 4’s than sitting hence lowering blood sugar and requiring less of an insulin spike.
Insulin is bad as it inhabits fat burning.

It’s important to differentiate between low carb as a diet technique (bad) and low carb as an endurance adaptation technique (maybe good, maybe bad).
You don’t need to do the former to try the latter.

Low-carb / overnight-fasted rides do train your body to use more fat. But they will dig you into a hole if you don’t cap the intensity.
I used to aim for around 55%-60% of ftp and built them up to 6hrs.

The other option is to do them on an overnight fast for a couple of hours at a slightly higher intensity (z2), then before you bonk, start smashing carbs. Because your glute 4’s are open, your body will absorb them in no time and you can finish your ride however you like.

It gives you amazing confidence to know you can ride for hours with no food if you really need to.

I don’t pretend to understand many words but I love Peter Attia and his guests pumping their deep knowledge into my ears when I ride 🤣

This episode about insulin resistance is fascinating.

https://podcasts.apple.com/gb/podcast/the-peter-attia-drive/id1400828889?i=1000586933595

Tldr- even half the ‘healthy’ and skinny population is insulin resistant but exercise is still the best hack there is.

I laughed at this too. Maybe your ride has made you vitamin B deficient or something

Can I share GIFs?

Edit: apparently so 😎

we are all different

That’s been my point all along. Our responses to stimulus and the resulting hormones varies a lot for the reasons you state. You need to work out what works for you.

low carb as a diet technique (bad)

That’s controversial, why do you say that?

Because even if you condition yourself for years. you are always going to be limited on the top end on a low carb diet. Your ability to store and replenish glycogen is impaired.

This may not matter for ultra endurance but for almost everything else- it’s the carb fuelled efforts that win you the race.

it’s the carb fuelled efforts that win you the race

Or, importantly for me, provide the most fun bits of a bike ride.

For sure 😀

Low carb is like building the worlds strongest foundations for a mansion and then living on top of them in a tent 🤣

So much bollocks in such a small amount of text!!!

can you point me to the scientific literature that shows where I have gone wrong?

glucagon

Hormone involved in regulating blood glucose level. Think of it as the opposite of insulin.

Low-carb / overnight-fasted rides do train your body to use more fat. But they will dig you into a hole if you don’t cap the intensity.
I used to aim for around 55%-60% of ftp and built them up to 6hrs.

The other option is to do them on an overnight fast for a couple of hours at a slightly higher intensity (z2), then before you bonk, start smashing carbs. Because your glute 4’s are open, your body will absorb them in no time and you can finish your ride however you like.

+1 This is exactly how I train(ed) for long distance MTB and also weight loss. 3hrs going up to 4hrs Z2 fasted with a 750ml water first and a 500ml energy drink for the final hour, plus emergency gel on standby.

I’m all for getting fitter, but this all sounds like some kind of purgatory 🤣

So much bollocks in such a small amount of text!!!

can you point me to the scientific literature that shows where I have gone wrong?

Yes my thought was it might be more useful (and polite) to explain why it was so much bollocks. Though my twopennorth would be that it’s not eating carbs that “switch your metabolism” it’s the intensity of the exercise.

Though my twopennorth would be that it’s not eating carbs that “switch your metabolism” it’s the intensity of the exercise.

It is that. At low intensity exercise the slow twitch fibres predominantly use fat as an energy source while the fast twitch fibres are not being engaged. As you increase the intensity of the exercise the muscles start to use glucose over fat. You take in carbs as part of the normal diet while Gluconeogenesis occurs to help maintain blood glucose levels if there isn’t enough glucose in the diet.

I thought the TR version was exhausting but this thread must be the left half of the bell curve.

Eat sugar and ride your bike a lot, sometimes hard.

Crosshair, stop trying to canvas for the joys of eating disorders.

What the heck are you on about @continuity ?

Even Coach Chad says fasted rides have their place as a tool.

Fasted Cycling: Program Your Body to Burn Fat with Fasted Training

I’ve even said don’t do (faddy) low carb diets.

I think you may have a reading comprehension issue.

I’ve tried one Z2 “run”, really tricky. Fast walk wasn’t enough, jog at such a slow speed was difficult. Felt more knackered than Z3.

Back on topic- there’s so much amazing content out there about the benefits of this style of training.

This video below (non cycling) summed it up for me when he says, you don’t realise how unfit you truly are until you start this sort of polarised 80/20 z2 heavy training! Then after a while, you get back from 3hrs and realise you could do another 3 hrs no problem.

Because even if you condition yourself for years. you are always going to be limited on the top end on a low carb diet.

Oh, yeah, that’s definitely true. A low carb diet is only ever a weight loss tool, not a long term thing, in my view.

Though my twopennorth would be that it’s not eating carbs that “switch your metabolism” it’s the intensity of the exercise.

It is that.

Sorry if I’m misunderstanding but isn’t that contrary to your post?

“Carbs will just switch metabolism to glycolysis rather than beta oxidation” – i.e. it’s eating carbs that cause the switch not the intensity of exercise.

I’m in bed the now doing nothing but rest and typing this. My body is primary using fat as an energy source (apart from some parts like the brain that prodominantly uses glucose). If I have a can of sugary coke my body will switch to using glucose in order to keep my bloody glucose level constant.

Now in exercise if you are doing low intensity low VO2 stuff your body will still prefer to use fat as an energy source. If you do zone 2 and take in carbs the body will use the carbs to maintain a constant bloody glucose level rather than metabolise fat.

If you then go to high intensity/high VO2 stuff the body switches over to glucose rather than fat.

Slow twitch fibres for endurance like zone 2 primarily use fat as an energy source. Fast twitch fibres used in sprinting use glucose as an energy source.

That probably doesn’t make it any clearer

If I have a can of sugary coke my body will switch to using glucose in order to keep my bloody glucose level constant.

AIUI your cells always use glucose, that can come from your blood stream or from breaking down glycogen or fat. Glucose is a bit toxic over certain levels so your pancreas secretes insulin pretty quickly. But if you drink a lot of sugar the insulin promotes your cells to convert glucose to glycogen and store it. But if they are full, then it gets converted to fat. The glucose doesn’t hang around in your blood until you use it, if you’re not diabetic. If you are, then it can, and you get a load of problems because it wrecks your blood vessels. However the insulin also inhibits lipolysis so your cells will prefer stored glycogen, so that is also an effect, but I don’t think it’s the mechanism for keeping blood glucose constant.

If you do zone 2 and take in carbs the body will use the carbs to maintain a constant bloody glucose level rather than metabolise fat.

It’s not binary. In the ‘fat burning zone’ you might be using 60/40 fat/glycogen and in the ‘carb zone’ it might be 30/70, but those numbers depend on the person and their physiology. Eating carbs does inhibit lipolysis or fat burning, but it doesn’t switch it off.

As far as I know, taking on carbs in the first 45 mins of a ride can inhibit the use of fat somewhat, but you aren’t burning 100% fat so after that your glycogen will still be depleted a bit and you will benefit from taking on carbs. At least, some people will. There are people who can ride all day purely on fat stores – but I’m sure they are depleting glycogen a bit, they’ll just replenish when they get home.

This is worth a read:

“Carbohydrate and fat utilization during rest and physical activity”

https://clinicalnutritionespen.com/article/S1751-4991(11)00006-0/fulltext

Z2 is primary fat using. You are using slow twitch fibres which use fat as an energy source. I wouldn’t be carb loading while doing it. You want the fat to get used and increase the numbers of mitochondria in the cells. Carbs will just switch metabolism to glycolysis rather than beta oxidation.

Zone 2 will use muscle fibres of both types. In any case the difference between the two is not a hard border it’s a continuum.
Eating when riding is not carbo loading.
Carbs do not switch anything, it’s not like turning a light off or or on as one pathway starts another does not stop. You will be metabolising carbs even in zone 1 and fat in zone 6 it’s just the proportions that change.

As molgrips says it’s not binary

It’s interesting reading this thread and as a non-sports science/metabolic expert trying to follow.

I suppose the thing is (especially this time of year) us tubby desk bound gits periodically take a look at the litterateur and advice flying about and try to lash together some sort of training and diet plan.

With that in mind is the overarching advice still that “generally” doing a large volume (let’s measure it in time rather than miles) of Z2 activity will help with both weight loss and endurance? I reckon I could rustle up 2-3hrs most weeknights, if I were motivated to sit on a trainer in the garage, listening to podcasts churning out a steady Z2 effort. Before I embark on a January of lost evenings, have I interpreted the advice anything like correctly?

With that in mind is the overarching advice still that “generally” doing a large volume (let’s measure it in time rather than miles) of Z2 activity will help with both weight loss and endurance?

Yes. We are all nerding over all this, but essentially yes you need a lot of slow miles and a much smaller amount of high intensity. The low intensity isn’t just to make it easier, it trains your body in a specific important way but it takes a long time which is why you need a lot. The high intensity does make you faster quickly, but it’s demanding on your body which is why you shouldn’t do a lot.

I reckon I could rustle up 2-3hrs most weeknights

That’s a lot. I’d say 6-8hrs a week is enough to have a really big impact for a recreational cyclist especially if you have never done it before. However, if you feel like it then go for it as long as your body can take it. You might find your knees get a bit sore riding on a trainer that long.

Yes for endurance. There’s some studies showing that people who maintain a little intensity go on to hit a higher peak (with their high intensity work) later in the season than those that do just Z2. So anything along the lines of 80/20 90/10 will be good.

For diet- not necessarily. It’s just calories in, calories out. So obvs high intensity burns more in the same time but over a session inc warm up, cool down and rest periods- the difference may not be that great. Your body may burn more post exercise calories with HIIT too as it takes energy to get back to homeostasis.

I like low Z2 for a weight-loss phase because you can do it day in day out without ever really getting glycogen depleted and craving a binge to restock. And as you get fitter with it, you can cut right back on the carbs mid ride. That enabled me to build up enough of a deficit to be able to pretty much eat normally with the family etc. It never felt like I was dieting.

You want the fat to get used and increase the numbers of mitochondria in the cells.

For me, the ‘increase mitochondria’ is the main point of the Z2*, not weight loss or becoming fat adapted, but I hadn’t heard anything about choice of fuel altering or impacting mitochondria development? From what little I think I understand that doesn’t seem correct?

*actually the main point is just achieving some sort of consistency with my riding that isn’t impacted by constantly over-reaching on the turbo mid-week 🙄

With that in mind is the overarching advice still that “generally” doing a large volume (let’s measure it in time rather than miles) of Z2 activity will help with both weight loss and endurance?

ime, as someone reading the tech of this thread out of interest and reference to what else I’ve read (skimmed) over the years but with no detailed knowledge of the physiology of it all, fwiw –

I’m not sure if large volume is the point, ime 2 rides of 2hrs or 1x2hrs + 1x3hrs a week would maintain my base as well as being where I started with all this. I’ve done much more over periods but I didn’t find it changed my general base, it was done in years when I was training for long distance events or rides and wanted the time on the bike for conditioning.

Yes, Z2 is the key to endurance ime. Physically as well as mentally – when you can ride 80-100 miles at base pace and not feel tired (not compared to 100 miles with an eye on the clock) it changes how you see distances.

Definitely measure Z2 in time not miles. I have no idea of my winter mileage but I generally do >6-8hrs at base pace a week Nov-Feb.

I don’t think Z2 time helps with weight loss in itself. I drop weight more noticeably when I’m doing a weekly threshold session among my other riding, 20-25mins in total at LT. Feel like that revs up my metabolism more or for longer overall.
Z2 base miles do enable me to ride a long way on very little as well as ride further in spring/summer so overall it’s good for total calories burned but I don’t see Z2 as a weight control method in itself, not personally.

Some of my Z2 rides are in the morning and fasted for 1.5-3hrs. I did a winter where I was up to 6-7hrs Z2 after 22hrs fasted (dinner night before, set off to finish the ride 4-5pm and eat in the last 5-10 miles) and doing that at least every other weekend Jan-Feb. I don’t think it did me much good aside from knowing it can be done. Endurance that spring-summer was fine but I felt like I lost some power, though I wasn’t bonking there’s possibly muscle metabolism or damage in later stages of those long unfuelled rides? Either that or cumulative fatigue. Anyway, I very rarely do it now.

Most training guides I read have Z2 endurance sessions of 2-3 hours. Perhaps 2-3hrs in Z2 at a time is all we really need.

My own experience of started fasted riding 1-3x a week, around 2hrs each time at either Z2 or mixed SS MTB pace, was that it was part of a period where my ability to ride on reserves improved hugely. While I know fuelling makes me faster and less physically stressed overall I’m happy riding at a steady pace for 2-3hrs on nothing these days. Add in a few efforts, ride SS MTB or or up the pace to a brisk social ride and I’ll get through a Belvita type cereal bar an hour or every 90 mins.
These days I’d say the Z2 time is the main gain for endurance, unsure of how fasted and Z2 inter-relate though.

I may be wrong here, but I think mitochondria development is influenced by intensity – more at lower intensities and less (moving to muscular development and lactic response/shuttling) at higher intensities.

Either way is not a hard line as stated above, a varies between individuals but is roughly recorded as Lactate Threshold.

Both systems support each other – going faster for longer needs endurance to underpin strength and vo2max.