[Closed] Exercise and fat use

A couple of key thoughts I've formed over the years.

1. Don't aim to lose weight during exercise, not unless you're doing >15hrs per week anyway, aim to lose weight between exercise. Exercise is a tool to shape your health, energy use, state of mind, lean mass for your life between exercise sessions.

2. Human bodies don't burn fat, they convert it by mass into 84% carbon dioxide and 16% water which is then expelled from the body. You lose most of the mass when you breathe out. This is actually only true if you're not pushing the body into ketosis which breaks down the fat in a different way, but either way it is helpful to remember that fat utilisation is something that can happen 24/7 not just during exercise.

Training for optimal power output / energy use during endurance cycling is another matter.

I am certainly no expert but if you eat beans for example the digestible parts will be broken down by enzymes into glucose and other smaller sugars for absorption into the blood.

Right, and all this takes time. This is what the glycaemic index (and to a lesser extent the insulinaemic index) is all about. If you eat glucose it's already in the form it needs to be so it immediately (within a few minutes) goes from your stomach lining into the blood. If you eat beans, all the bacteria lower down your gut have to digest it first which might take ages, 12 hours or so. And all our gut bacteria are different - for example, beans don't make me fart ever.

Insulin stimulates uptake of glucose by cells (either fat cells or other cells that need it) and this takes a bit of time, which is why there's a lag in the system. You end up with an excess of insulin after your blood glucose has been absorbed, which means that the cells keep absorbing it and you end up with blood glucose a bit too low. And this makes you hungry. This is why people say they can eat a big meal then feel hungrier a few hours later than if they'd had a small meal.

If the glucose enters your blood slowly, then the system does not have to respond quickly, so there is less excess insulin and your blood sugar can return to normal background levels without the dip.

This all applies to when you are NOT exercising, because your cells are using fatty acids created by lipolysis (fat burning) AIUI. But when you exercise hard your muscle cells use up their glycogen stores. Then, if you take on carbohydrate the insulin is a GOOD thing because it gets the glucose into your muscles quickly. This is good for sustaining hard exercise. And it doesn't matter if you are a pro or not - hard means hard relative to your maximum ability.

But it does depend on your physiology. If you are an endurance type like my mate Nigel, your muscles have lots of type I fibres so they are good at using fat as an energy source. But you have not many type II fibres so your ability to use glucose is actually quite low. This means that if you ride hard you don't deplete your glycogen stores very quickly, so you can smash out two hours without bonking and without needing food afterwards. But your hard 2 hours will be a sustained pace.

If you're a sprinter like me, then you have lots of type II fibres which means when you smash it you're using up a lot of glycogen in your cells. So you will bonk quickly unless you are topping up the glycogen, and if you dont' top up enough either during or just after exercise you'll spend the rest of the day with low muscle glycogen and this makes you very hungry indeed (at least it does me) and you will struggle to recover. In fact, if I restrict calorie intake too much (cos you know, people keep telling me to move more eat less) then I get permanently fatigued, my legs always ache and my resting HR is always elevated by 5 beats or so. And eventually I start feeling cold as my BMR drops, and the energy I can expend on the bike goes down. This is why eat less move more does not always apply, especially to people who are already fit and active and just want to get leaner.

All the above is what TJ does not appreciate, by the way - he is a casual rider, which is fine, and he thinks everyone else is a casual rider too so all this is waffle. But it's not, and the effects will be felt by anyone who is training to improve regardless of how fast they actually are. You don't have to be a pro to get benefit from understanding this - it's the difference between training and simply riding for the fun of it.

I think the general advice fits for casual cyclists but as with everything there is a normal distribution. I think the whole keto thing seems dangerous because when people talk about what they eat it seems to contain lots of bacon and other processed meats and loads of saturated fats, these things are proven to be bad for us. Eating a healthy balanced diet and lowering simple carbs when not exercising and eating a bit more carb before and during exercise is just sensible to restrict calories and as you say insulin spikes.

I agree in general with what you wrote but extreme diets always look bad. Boosting fat metabolism with the odd fasted ride may well help endurance athletes but for most stw nodders like me I doubt it helps.

If you are an endurance type like my mate Nigel, your muscles have lots of type I fibres so they are good at using fat as an energy source. But you have not many type II fibres so your ability to use glucose is actually quite low

This is where I start to disagree. I find it hard to understand how respiration isnt just respiration. Cant say why I disagree though. Type 2 would do more anareobic respiration, wonder what happens to the lactate later.

Glycogen degradation was most pronounced in type I fibres

Which is the opposite of what you percieve! I think wecall agree its complicated!!
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1180046/

All the above is what TJ does not appreciate, by the way – he is a casual rider, which is fine, and he thinks everyone else is a casual rider too so all this is waffle.

I think you are arguing at crossed purposes, boosting endurance through low carb diet, but eating carbs and a balanced diet is fine. Using Keto diets for weight loss and eating more things that are proven to be bad for us is bad and this is I think TJ's position.
Low carb is fine but thats not Keto

eating carbs and a balanced diet is fine.

Yeah it's fine and indeed good, as long as you are at the weight you want. If you aren't, then there are a number of ways to do this, some more effective than others depending on a wide range of factors. This is my point.

Using Keto diets for weight loss ... is bad

I have yet to see evidence on this thread that actual ketogenesis is bad. Not eating vegetables is bad, but we already know this. And we've been shown that you can be ketogenic whilst still eating vegetables, haven't we?

This is where I start to disagree. I find it hard to understand how respiration isnt just respiration. Cant say why I disagree though. Type 2 would do more anareobic respiration, wonder what happens to the lactate later.

I am not a biologist so I only have an athlete's understanding of this. It was explained to me by a sports science professor at Cardiff Met - your ratio of type I to type II varies genetically, and whilst if you have more type II you can train to shift towards having more type I, you cannot train the other way round. Which fits in with long standing anectodal evidence from the sports world - pure sprinters are born not trained.

Glycogen degradation was most pronounced in type I fibres

I don't think that line says what you think it says. It doesn't say how long the subjects exercised for, just that they went 'until exhaustion or up to two hours'. And they used single leg which we know is quite hard. And it doesn't show what kind of athlete they are so I am not sure what we can draw from that. They do say though that 'fibre-specific differences are evident in prolonged submaximal exercise'. Before I knew about base training I was doing all my riding fuelled on mostly glycogen (as I found out in a blood test workout) and yet I could still do the same ride at the same pace as someone else. But very different things were happening in my muscles.

Boosting fat metabolism with the odd fasted ride may well help endurance athletes but for most stw nodders like me I doubt it helps.

Any cyclist, STW user or not, would benefit from targeted training. I've said many times what happened to my lactate threshold (measured with blood tests) when I was shown how to do base training properly. Training works regardless of how fast you already are.

It doesn’t say how long the subjects exercised for, just that they went ‘until exhaustion or up to two hours’.

So it does say how long they exercised for?

Glycogen degradation was most pronounced in type I fibres

I don’t think that line says what you think it says.

Why would they put it in then?

By the end of exercise, glycogen concentration was 82.4 +/- 45 mmol glucosyl units (kg dry wt)-1 in type I fibres and 175 +/- 62 mmol glucosyl units (kg dry wt)-1 in type II fibres

it doesn’t show what kind of athlete they are

It does.

It also says that the loss of glycogen was much more pronounced than type 2 in the first paragraph of the discussion so I think they are pretty sure.

And they used single leg which we know is quite hard

They used one legged cycling so that they could test the other leg as a control.

And we’ve been shown that you can be ketogenic whilst still eating vegetables, haven’t we?

Have we?
Its the high levels of animal fat and processed meats people seem to eat on it that worries me.

when I was shown how to do base training properly

Care to offer a synopsis of 'proper' base training? Genuinely curious.

I'm feeling a lot better for increasing my volume (between 9-10hrs a week but could easily increase and plan to) but mostly very easy (zone 2). I do also plan to start working some sweetspot in for 2-3 months before hitting the turbo over the winter.

My legs feel great despite doing very little high intensity, but I've got a nasty feeling that's just because I'm just learning to be efficient a slow speeds!

Like the OP I've been trying to figure out how to lose weight whilst also exercising, unfortunately have learned that anything over an hour or so fasted (however gentle) needs fuel intake, otherwise I end up an cranky, grumpy mess afterwards due to low blood sugar. I think I'm going to go back to intermittent fasting as an 'easy' method of calorie restriction, and eat normally when I'm riding.

I find this thread interesting and would like to loose a pound or 7. I ride fast and watch what I eat but I'd like to shift some mild biscuit/ pizza retention. Think I do what is mentioned above and ride too hard always depleting my glycogen stores - never been good at base rides as I get bored/ like going fast...

I have a question which may be stupid, but is something I've never got my head around much - If I go for say a 3hr base road ride, keeping Hr and effort down, but then throw in a few 5 minute maximal efforts or go for some Strava segments 'cos there's a tailwind and I'm bored...Is this still a base ride? Or does it negate the effects of base adaption?

Is this still a base ride? Or does it negate the effects of base adaption?

For me, the purpose of base rides is to keep them so easy you can do lots of them! I guess if you start segment chasing or throwing in efforts occasionally then you might not be able to do that every day.

Edit: I'm beginning to lose faith in regular base rides as a means of weight loss, I think the chat above about adaptation etc. rings true as I've been doing increasing volumes of fasted base rides (commutes or short morning lockdown loops) and it's made very little difference to my weight.
Various attempts at calorie restriction and cutting out carbs (I consider myself 'liberal low carb' 😉 ) are making slow inroads though...

So it does say how long they exercised for?

Some time up to two hours that could be anything from 10 minutes to two hours, and we don't know what percentage of FTP. Anyway this is not helping. I could easily be wrong about muscle fibres but something a bit more developed would be nice.

Care to offer a synopsis of ‘proper’ base training?

I did the traditional base training which is lots of long slow riding. But I used a power meter which is pretty important, especially for someone like me. I had my lactate threshold measured via blood testing, which is the power at which your blood lactate starts to rise (my chart though was anomalous in that I was *always* producing lactate at all powers, which my coach had never seen before, so we had to make a bit of a guess), and then base training is riding at that power or a bit more for as many hours as you can fit in which in my case was about 7-10 depending on what I managed.

After doing that for 8 weeks I developed a proper lactate curve which meant I was able to ride up to 210W or so without producing lactate at all. Interestingly I only restricted calories somewhat, I didn't restrict carbs (this was a long time ago) - this is where TJ gets his 2kg of sugar a week or whatever from (it wasn't that much). It's also one of the most successful weight loss periods I had!

Many years later long after falling off that wagon I did the low insulinaemic diet, and lost a similar amount also whilst taking on carbs whilst riding, but my endurance improved again, subjectively. And then whilst doing more fasted riding my endurance improved still further, subjectively also. So I think that base training works to improve endurance by training fat metabolism/increasing mitochondria (as everyone knows) but I also think fasted/low carb riding does too - maybe more effectively, maybe not. But it does require some adaptation at least in some people, it might be too hard to just jump in.

Think I do what is mentioned above and ride too hard always depleting my glycogen stores – never been good at base rides as I get bored/ like going fast…

You are probably a sprinter, and are fairly well built, right?

I have a question which may be stupid, but is something I’ve never got my head around much – If I go for say a 3hr base road ride, keeping Hr and effort down, but then throw in a few 5 minute maximal efforts or go for some Strava segments ‘cos there’s a tailwind and I’m bored…Is this still a base ride?

I am not sure, but I think it will wreck any calorie restriction you are trying to do. I find that I can do a proper base ride i.e. long and slow, if I am restricting carbs/calories and deal with it fine, but if I go into the red more than a little bit it will cause different training stress and eventually end up in the excessive hunger/fatigue/unable to recover situation and then I'll have to eat some carbs. And eating carbs just makes you want to eat more carbs, so then I'll eat to satiety which means I'll only end up maintaining weight.

But this is all personal and I'm sure that I've heightened certain responses by trying to too much on not enough of the right fuel.

I find I can ride hard everyday for a week or two, like going on a training camp in the mountains, eat very little and even if it's swelteringly hot somehow I will not loose any weight...in fact some times I will gain weight, but I will be faster...I might be weird. In answer to above, I'm no sprinter, more of a Rouleur, used to be very light..but build muscle easily, yet struggle to shift fat on the bike.

Oh dear - I dipped back in

All the above is what TJ does not appreciate, by the way

I have never said that Molgrips.

edit - AA gets it

I am arguing against Keto and I have in the past argued against relying on refined sugar for your main fuel.

I think you are arguing at crossed purposes, boosting endurance through low carb diet, but eating carbs and a balanced diet is fine. Using Keto diets for weight loss and eating more things that are proven to be bad for us is bad and this is I think TJ’s position.
Low carb is fine but thats not Keto

MOlgrips - it was over half a kilo of refined sugar - all I did was add up the number of cans of full fat coke and maltodextrin that you said you took - it was at least half a kilo o aweek of refined sugars from those two sources. 35 g of sugar in a can of full fat coke. 40 g of maltodextin or other sugars in a litre of isotonic drink at least

And I had better back out again for mine and Moleys sanity. Love you really Moley!

I spoke to my doctor today. She’s impressed with the weight loss and made no comment on my method of achieving it. At my request I’m getting my cholesterol checked next week and I’m interested to see the results.

I'd also like to point out that TJ is neither fast nor skinny 🙂

When I drink maltodextrin I calculate how much I need based on how long I'm riding for and how much glycogen I'm likely to be using on that ride. I don't just chug it cos I like it or I think it makes me into Peter Sagan. I do this because it stops me being hungry after the ride which means I don't end up eating MORE than I've used up.

I'm not an idiot.

Edit: I’m beginning to lose faith in regular base rides as a means of weight loss, I think the chat above about adaptation etc. rings true as I’ve been doing increasing volumes of fasted base rides (

I would imagine mixing it up regularly whilst still having proper rest is the best advice.

I spoke to my doctor today. She’s impressed with the weight loss and made no comment on my method of achieving it. At my request I’m getting my cholesterol checked next week and I’m interested to see the results.

No doubt having dropped 30kg most metrics will have improved. If you have 30kg of excess fat you are pretty unhealthy, now you have lost it you will be more healthy. Undoubtedly a diet that has worked for you is a good thing. If you can keep the weight off and move to a lower fat and lower processed meat intake you will have it cracked. Well done. But it doesnt mean the keto diet is healthy, any weight loss from where you were would have improved things and no doubt your doctor is really pleased.

Fat isn't necessarily the enemy it has been made out to be...

https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good

But it doesnt mean the keto diet is healthy

There isn't "a" keto diet in the same way that there is an Atkins Diet (tm), there are simply ways to eat that are ketogenic. Seems like doomaniac's diet is healthy (if the sample dish he gave was representative) whilst also being ketogenic.

When I drink maltodextrin I calculate how much I need based on how long I’m riding for and how much glycogen I’m likely to be using on that ride

I can't use energy drinks, the number of pee stops gets ridiculous! Annoying as they seem the simplest way to combine hydration and fueling...

Provide me with links to reputable peer reviewed journals by proper scientists and I will read and learn.

i've done this on other threads where you've asked and heard nothing back:

https://singletrackmag.com/forum/topic/talk-to-me-about-keto/page/7/#post-11055202

you also don't seem to have backed up the claim that keto is dangerous:

Being in ketosis damages both brain function and other body systems. It will also screw up your metabolism leading to yo yo weight gain / loss.

singletrackworld.com/forum/topic/intermittent-fasting-keto-and-timing-of-exercise/#post-10247870

Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome

Compelling evidence exists for the use of nutritional ketosis for the management of weight and the components of metabolic syndrome. Through the utilization of alternative fuel sources, namely ketones, we can capitalize on the antagonistic relationship of high glucagon and low insulin levels that promote breakdown of fat for fuel, sparing of glycogen in muscles, and de novo gluconeogenesis as needed. Further research is needed into long-term adherence and practicality of VLCKD, but the current results are promising for weight management, lipid profiles, and insulin sensitivity

s a species, we have metabolic flexibility with the capability to rely on alternative fuel sources for energy. Humans are not dependent on exogenous sources of glucose for optimal function; rather, we have evolved over millennia to adjust to changing conditions and adapt to both scarcity and abundance. As Dr. Randle explained in the Lancet in 1963, “Substrate metabolism in the normal human body is flexible. Our bodies have evolved to utilize different fuel sources depending on their availability.”7

Humans have evolved with the capacity for metabolic flexibility and the ability to use ketones for fuel. During states of low dietary carbohydrate intake, insulin levels remain low and ketogenesis takes place. These conditions promote breakdown of excess fat stores, sparing of lean muscle, and improvement in insulin sensitivity.

Original research into a ketogenic diet began in the early 1900s as a way to manage epilepsy and minimize seizure activity. By inducing ketosis, patients had mitigation of seizure activity and improvements in cognitive function, highlighting the capacity for ketones to provide energy to the brain.15 From the 1960s onwards, very low carbohydrate ketogenic diets (VLCKD) have become more commonly known as a methods for obesity treatment. Recent work over the last few decades has provided evidence for the therapeutic potential of ketogenic diets in many pathological conditions, including diabetes, PCOS, acne, neurologic diseases (epilepsy, Alzheimer’s, CVA), cancer, and the amelioration of respiratory and cardiovascular disease risk factors.15 The possibility that modifying food intake can reduce or eliminate need for medications, which often carry significant side effects, calls for serious investigation. Dietary carbohydrate intake has been studied with variable findings, which is often due to lack of standardization of carbohydrate intake and inability to confirm ketosis without checking blood ketone levels.

TJ said:

Ketosis is the presence of excessive ketones in the body caused by starvation, fasting, alcohol binging and uncontrolled diabetes. Ketoacidocis is when the levels are so high as to overwhelm homeostasis and cause the blood PH to alter. The first is harmful if prolonged, the second dangerous and life threatening. Ketosis is the first stage on the way to ketoacidosis.

Tj can you point me in the direction to claims that ketosis is the first stage on the way to ketoacidosis

Tj can you point me in the direction to claims that ketosis is the first stage on the way to ketoacidosis

It isn’t they’re similarities but it’s not first stage and it’s not Ketoacidosis.

TJ you really need to calm down in threads like this.

I can’t use energy drinks, the number of pee stops gets ridiculous! Annoying as they seem the simplest way to combine hydration and fueling…

I rarely need to stop to pee. Just about the only thing in which gifted with truly world class ability is sweating. I sweat a lot, consequently I can ride hard in just about any climate; not needing to pee is a side benefit 🙂

I've had a good week. About a kg down, quite possibly because I've only done one ride.

Wait, you've LOST a kg because you've only had one ride? Are you trying to imply that by not riding you've been able to restrict calories more?

I seemed to gain 2kg on my holidays, but yeah, there were a few beers and bags of crisps (and one chippy) but also two big, hard gravel rides where I though for sure I'd be in a big calorie deficit...

Wait, you’ve LOST a kg because you’ve only had one ride? Are you trying to imply that by not riding you’ve been able to restrict calories more?

Yes. I've stuck to the diet really well.

I have done a bit of walking and I worked up a hell of a sweat sawing up a 8x4 sheet of 20mm ply into shelves the other day. Taht was like an hour long KB workout.