[Closed] Weight loss during exercise

water, dehydration

Sweat primarily - between 0.8 and 1.4 litres per hour is the 'normal' range apparently

sweaty stuff

3lbs is what - under 2 l of water? - yes it could well be - you lose water from breathing as well

One year working in a really hot environment I was drinking 3-5 l of water a day and peeing 3 drops of concentrated piddle all day - I was losing all that water in sweat and breathing

3lbs = 1.3kg of water which is 1.3litres of water.

I think the average person can probably run 5 miles in around 1hour.

So if you are a particularly sweaty person I can see it being plausible that the weight loss is from sweating and dehydration.

And you are right there are a lot of variables in play when weighting you self. Try to stick to the same routine everyday to make it as fair as possible.

Don't get too hung up day to day weight changes. Look at the trend over the week, month etc... Keep a diary and plot it on a graph or use a app to track it.

Its very easy not to notice a 100g reduction each day as you might more hydrated than before or haven't finished your bathroom routine one day before measuring etc... But over the course of a couple weeks you'll see that 1 - 2 kg difference.

I think I read somewhere you also exhale burnt fuel be it fat, sugars or protein etc

Weigh yourself in the morning. You'll notice some days you'll be a kg or more heavier, others less. It's the downward trend you need to watch. I've lost 6kg over the last couple of months, more to go, but some days I can be a kg or more heavier, some days a kg less. The weight at the minute varies between 5-7kg lost.

In addition to dropping water weight you will also burn carbohydrate that is stored in the liver and muscles (glycogen) during exercise - you can store around 600-800ish grams in both combined so depending on the length and intensity of the exercise you can drop that amount of weight and easily a couple of KG of water.

You don't just sweat out the moisture/water, some evaporates and you breath out some too.

I think the average person can probably run 5 miles in around 1hour.

I think the "average" person in the UK couldn't do half that TBH. If you meant the average "moderately in-shape" person

I'm not worried by day to day fluctuations because the trend is nicely downwards but I had thought over a litre in sweat in a 45 min run seemed excessive. Seems I under estimated how much I can wring out of my tee 😀

Two things on the go here - sweat loss, as said - and also through respiration, but also bear in mind that when you store carbs in your system it's stored as glycogen in your liver and muscles, and the glycogen molecules are bound to water.

1g of glycogen needs 3 or 4g of water to store it. So when you use it up, that water is released. You could be storing about 500g of glycogen so using up all your stores (this would take a few hours of high intensity exercise and result in a complete bonk) could lose you 2-2.5kg.

In my experience this is about right - if I run for an hour, I don't take any drink and I sweat a lot, and I can easily come back 1-1.5kg lighter.

Long-term weight loss requires burning fat which will be converted to CO2 and water, then exhaled, sweated, or excreted.

Weight loss from a single exercise session will nearly all be dehydration.

In my case, every time I start out for a run, I suddenly need to take a huge ****. The jogging must loosen it all up or something.

To burn fat your body needs to be in a state of ketosis. You wont enter a state of ketosis if you consume any form of carbohydrate, as the body turns this into glucose, the bodys preferred source of fuel. The insulin response will push the glucose into the cells in muscles for energy, if these are full it'll store the extra as fat. Losing weight via exercise alone is very difficult.

https://thebloodsugardiet.com/difficulty-losing-weight/ Summed up nicely by Michael Moseley.

Diet is very important, high protein, high fat, low carbohydrate. And low GI carbs too.

Once you restrict carbs, you'll shed loads of water and the weight will drop off quite rapidly. Unfortunately the reverse it true too.

To burn fat your body needs to be in a state of ketosis. You wont enter a state of ketosis if you consume any form of carbohydrate, as the body turns this into glucose, the bodys preferred source of fuel

No, I don't think this is true.

Fat is your preferred source of fuel, glucose is only used when needed i.e. when you exercise above your lactate threshold. Eating carbs whilst exercising does increase blood glucose and hence insulin, which inhibits lipolysis somewhat, but I don't think it's correct to say that you can't burn any fat at all when you've eaten any carbs. This is not what I was taught.

Taking carbs does allow you to exercise more intensely for longer which may overall increase weight loss. For example if you can exercise at 800 calories per hour using 60% carbs (which you might have to replenish) you will burn more fat than if you are exercising at 500 calories per hour using 40% carbs.

Once you restrict carbs, you’ll shed loads of water and the weight will drop off quite rapidly. Unfortunately the reverse it true too.

When your glycogen stores are low your liver produces glucagon which is sort of the opposite of insulin - it promotes lipolysis i.e. fat burning. What I've found works well for me is to restrict carbs for a week or two and then to maintain carb intake (using low-GI sources naturally). If I continue to restrict too much I can't continue to exercise. This seems to keep the glucagon flowing and I can still ride fairly well whilst losing weight.

I think, when you exorcize you not actually 'burning' fat of course, but in effect you turn body fat into heat via the work of your muscles.

That said, if you're losing more than a Kgs in 24 hours, that will be dehydration. It's not unusual to sweat 3 to 4 litres per hour if you're really pumping away, which will result in a 3kgs to 4Kgs body weight loss unless you replace it.

That's why you see boxers running around in bin bags etc to make a weight, it's not because it's good for them, it simply dehydrates them for a weigh in. It wasn't long ago people would do the same to "lose weight quickly" which of course they did, but it wasn't body fat they were losing.

I was wondering how many steps to a ketosis dust up...

I was wondering how many steps to a ketosis dust up…

😂😂

I've noticed I seem to have 'put on' 2-3kg recently which can't really be explained by diet or exercise UNLESS my metabolism has changed a lot recently, e.g. I've not been eating terribly (by my standards) and exercise has been relatively consistent (in fact more running and weights than usual, which I had hoped would speed up weight loss because it's relatively new to me).

I'm reeeeeeeeally hoping it's water retention due to the bizarre hot and muggy weather conditions, a bit of clutching at straws googling does seem to suggest you can retain a good few pounds extra water.

That’s why you see boxers running around in bin bags etc to make a weight, it’s not because it’s good for them, it simply dehydrates them for a weigh in.

Yeah, a local gym owner had a brief career as a pro fighter but he was borderline between weight classes and did better fighting at the lighter weight. He was fairly tall so was constantly having to dehydrate to make weigh in. When he told me the stuff he had to do to drop his weight, I was horrified. Basically just constant starvation plus several days of dehydration before weigh-in, then frantic eating and rehydration to get strong enough to fight.

I think, when you exorcize you not actually ‘burning’ fat of course

No you are, just not that much. Not the 1-2kg people can record.

So. Much. Misinformation.

Every nutrition/diet thread goes this way. It’s no wonder people get confused.

The op asked about acute weight loss during exercise. This has been explained accurately above.

The rest about Ketosis etc. Nonsense and irrelevant.

I despair.

>I think, when you exorcize you not actually ‘burning’ fat of course, but in effect you turn body fat into heat via the work of your muscles.

The misconception (and apologies if this isn’t what you mean) is that when you burn calories, food, fat, whatever, it disappears. It doesn’t, that would break a fairly central law in physics and chemistry of mass conservation. When you burn food, you do chemistry on it and convert it into other stuff. Some of it becomes new you and the rest is excreted – as faeces, urine, breath, sweat and other bodily fluids.

If you are losing weight during exercise, then assuming you aren’t stopping for a toilet break, most of this is via water and CO2 loss in your breath and sweat.
Apparently you will breath out 840g of C02 and 160g of water for every kg of fat burnt:
https://www.sciencealert.com/where-body-fat-ends-up-when-you-lose-weight

I think, when you exorcize you not actually ‘burning’ fat of course, but in effect you turn body fat into heat via the work of your muscles.

To be fair this depends a lot on the nature of the exorcism. If you're dealing with a particularly violent, vigorous possession, you may have to go fully anaerobic to deal with it. You also need to factor in the psychic energy required, vigorous prayer, brandishing of crucifixes etc. It's not a straightforward calculation by any means and every exorcism is different. A meek, non-violent sort of spirit may simply willingly depart the host body without any significant struggle.

As usual with exorcism threads, this one has descended into a hellish mishmash of misinformation and heretical nonsense. I'll get my cassock 🙂

To burn fat your body needs to be in a state of ketosis.

nope.

https://thebloodsugardiet.com/difficulty-losing-weight/
full on bollox.

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From that website

The misconception (and apologies if this isn’t what you mean) is that when you burn calories, food, fat, whatever, it disappears. It doesn’t

It does in practical terms. We don't tend to worry about it after it's been flushed or our breath has been blown away.

To burn fat your body needs to be in a state of ketosis. You wont enter a state of ketosis if you consume any form of carbohydrate, as the body turns this into glucose, the bodys preferred source of fuel. The insulin response will push the glucose into the cells in muscles for energy, if these are full it’ll store the extra as fat. Losing weight via exercise alone is very difficult.

That sounds like a load of bollocks to me. Carbs aren’t the evil that some seem to think they are for starters. When I go through phases of going to the gym I’ll lose fat at a decent rate and don’t change my diet at all. My diet includes cakes and biscuits!

Never weigh myself though. Always take photos and measurements of various bits of me instead. YMMV but I find it a much better way to track progress with both weight loss and fitness gains

To be fair this depends a lot on the nature of the exorcism. If you’re dealing with a particularly violent, vigorous possession, you may have to go fully anaerobic to deal with it.

Thank you @BadlyWiredDog, possibly the most I have laughed at any post I have read on this forum (I haven't factored this evening's red wine intake into that calculation though...)

Thank you @BadlyWiredDog, possibly the most I have laughed at any post I have read on this forum (I haven’t factored this evening’s red wine intake into that calculation though…)

Hmmm... exorcism is no laughing matter, obviously. But you're very welcome 🙂

To burn fat your body needs to be in a state of ketosis.

That sounds like utter drivel, spouted by Atkins diets fanatics etc.

It is footflaps - ketosis is an abnormal and dangerous state. Mucks up your body chemistry.

I've lost 22kg since Jan last year and I've eaten more sugar in that period than any other period in my life.

If running unless you are extremely fit and able to run whilst maintaining a ver low heart rate then you are not touching your fat reserves during exercise so any weight loss during exercise is 100% water. You will only actually consume fat to replace the energy following exercise....assuming you don't go and stuff your face straight after. Try to push out the time from finishing exercise to eating or consuming anything but plain water. If your goal is to lose weight you cannot escape the fact you have to spend a proportion of the day hungry! Thats where I fail. Part of losing weight is to also shrink the size of your stomach and digestive system. I have a low tolerance to feeling hungry. All the skinny/thin people I know can sit there for hours complaining about being hungry. They can tolerate being hungry and sometimes even skip meals. I can't do that. As soon as I feel peckish I'll complain once before I go into hunting/scavenging mode.

Long-term weight loss requires burning fat which will be converted to CO2 and water, then exhaled, sweated, or excreted.

Weight loss from a single exercise session will nearly all be dehydration.

Agreed.

I love the fact that "proper" weight loss is all just CO2 and Water (i.e the actual mass leaving your body, through the breakdown of fats/sugars/proteins) being breathed or pooed out!!

DrP

If running unless you are extremely fit and able to run whilst maintaining a ver low heart rate then you are not touching your fat reserves during exercise so any weight loss during exercise is 100% water. You will only actually consume fat to replace the energy following exercise….assuming you don’t go and stuff your face straight after. Try to push out the time from finishing exercise to eating or consuming anything but plain water.

Wait, what?

Roughly speaking, you will burn fat when you are doing light exercise, but you can only get so much energy from fat. If you go over this level you start using up carbs, and if you need instant movement you rely on stored ATP.

If you ride hard, you'll be using up glycogen stores quickly. If you ride easily, you won't be, so much. If you deplete your glycogen you DO want to replenish that straight away, if you want to exercise hard again the next day or two. If you are trying to lose weight then you want to replenish the majority of your depleted stores but try and maintain a slight glycogen deficit. If you fast after exercise you're only going to get more and more tired and it's going to be miserable. If you eat fat after exercise you're not replenishing glycogen.

However, this varies hugely between people. I get slated on here for saying people's bodies are different, but it's pretty obvious when you look at people who do sport. This is why we have people who are great distances runners, people who are great sprinters, and there isn't really anyone who is great at both.

You are right MOley in that bit you quoted is balderdash 🙂

When I was a fit young thing, i would go for a 20 miler with a heavy bergen every Sunday. The weight difference before and after the run would be of the order of 7-10lb of bodyweight in around 3 or 4 hours, which was almost certainly only water, through breath and sweat, and blister juice.
No overall difference in bodyweight Monday to Saturday, just on tbe Sunday run.

I think I read somewhere you also exhale burnt fuel be it fat, sugars or protein etc

Is this a very long winded way of saying you breathe out CO2?

@BadlyWiredDog - Thanks for that one, I just spat my tea out everywhere laughing. Brilliant stuff!

Isn't it heat, water and CO2?

Same during recovery as your heart rate should be slightly elevated as your body repairs existing muscle damage and building new muscle as adaptation?

https://www.chemedx.org/blog/chemistry-weight-loss

Fascinating article on the latest understanding of how weight training increases fat loss. At a cellular level muscle cells, post activity, tell fat cells to metabolise by sending snippets of RNA out into the body, which fat cells pick up and react to.

https://www.nytimes.com/2021/07/21/well/move/weight-training-fat.html?smtyp=cur&smid=fb-nytimes

They noted plenty. Before their improvised weight training, the rodents’ leg muscles had teemed with a particular snippet of genetic material, known as miR-1, that modulates muscle growth. In normal, untrained muscles, miR-1, one of a group of tiny strands of genetic material known as microRNA, keeps a brake on muscle building.

After the rodents’ resistance exercise, which consisted of walking around, though, the animals’ leg muscles appeared depleted of miR-1. At the same time, the vesicles in their bloodstream now thronged with the stuff, as did nearby fat tissue. It seems, the scientists concluded, that the animals’ muscle cells somehow packed those bits of microRNA that retard hypertrophy into vesicles and posted them to neighboring fat cells, which then allowed the muscles immediately to grow.

But what was the miR-1 doing to the fat once it arrived, the scientist wondered? To find out, they marked vesicles from weight-trained mice with a fluorescent dye, injected them into untrained animals, and tracked the glowing bubbles’ paths. The vesicles homed in on fat, the scientists saw, then dissolved and deposited their miR-1 cargo there.

Soon after, some of the genes in the fat cells went into overdrive. These genes help direct the breakdown of fat into fatty acids, which other cells then can use as fuel, reducing fat stores. In effect, weight training was shrinking fat in mice by creating vesicles in muscles that, through genetic signals, told the fat it was time to break itself apart.

“The process was just remarkable,” said John J. McCarthy, a professor of physiology at the University of Kentucky, who was an author of the study with his then graduate student Ivan J. Vechetti Jr. and other colleagues.