Weight loss in training?

[xkcd]

Hey Guys,

its not about losing extra pounds on your body, but instead about the rate of weight loss during an exercise, i.e. how much weight do I lose per hour while cycling?

I am writing a script, where I want to include a varying weight, dependant on time of the activity, maybe even power and/or temperature based.
Think of strava calculated power, but with user-defined parameters.

So whats your take, 0.5 kg per hour? 1 % per hour?

thanks for your input!

[Singular]

I hear that you want to find some sort of answer to this, but you cannot have any that makes any kind of sense to use in a calculation - it is depending on so many factors that you won't be able to form a viable theory/hypothesis around it. You MIGHT be able to find some very loose correlation for one individual (you) with a lot of data points but bothing that can be generalized.

[xkcd]

I don't believe that to be honest. I mean, we can say how many calories are burnt during an hour of exercise, calculating from the power data for example. If that is possible, I thought that it would be also possible to calculate the weight loss in from the energy burned in form of Co2 exhaled for instance.

I just don't know the math behind it. (Sweating is something that I don't really want to take into account, too individual, you don't know if the water is evaporized or not...)

[Singular]

I don't believe that to be honest. I mean, we can say how many calories are burnt during an hour of exercise, calculating from the power data for example. If that is possible, I thought that it would be also possible to calculate the weight loss in from the energy burned in form of Co2 exhaled for instance.

I just don't know the math behind it. (Sweating is something that I don't really want to take into account, too individual, you don't know if the water is evaporized or not...)

There you have the reason for it. Keep in mind that you are not only losing fluid, you are also in many/most cases replenishing it too. That's two guesstimates that vary greatly between individuals.

[TobinHatesYou]

If you're frequently losing significant water weight on rides, you're doing it wrong. BikeCalculator already has a "weight loss" field as well.

[xkcd]

Maybe to clarify, another reason I don't look at water replenished is that the weight I am regarding is the total system weight, rider + bike + everything he carries.

So I want to know how much the system weight of a rider goes down during a ride, to calculate the power needed for a hillclimb for example.

edit: regarding bikecalculator, useful. thanks, if the mass of say 1000 calories is really significantly less than 0.1 kg, I will not consider it.
I am not calculating static, averaged efforts though but the whole ride based on GPX data.

[Singular]

Maybe to clarify, another reason I don't look at water replenished is that the weight I am regarding is the total system weight, rider + bike + everything he carries.

So I want to know how much the system weight of a rider goes down during a ride, to calculate the power needed for a hillclimb for example.

Well, sweating would be the greatest contributor to weight loss during riding (along with comfort breaks) - simply overlooking these and trying to quantify glycogen/fat loss (that is also to a large extent connected to fluid) is straining at a gnat.

If you're frequently losing significant water weight on rides, you're doing it wrong. BikeCalculator already has a "weight loss" field as well.

The weight loss field is merely a translation of expedited calories to fat (weight), and it's unfortunately not really that simple in real life.

[Andrew69]

edit: regarding bikecalculator, useful. thanks, if the mass of say 1000 calories is really significantly less than 0.1 kg, I will not consider it.
I am not calculating static, averaged efforts though but the whole ride based on GPX data.

The maths you are looking do to is ridiculously complex as it is highly variable on so many factors including (but not limited to);
Glycogen stores levels (eg topped off or partially depleted due to overnight fast)
Training history
Fat adaptation due to diet
Training intensity
Heat
Rate of glycogen replenishment
Rate of hydration replenishment
Individual variances between athletes
Terrain...to name but a few

The reason you cant find any data on it is that it is simply too hard to calulate and of little consequence in the grand scheme of things

[TobinHatesYou]

The weight loss field is merely a translation of expedited calories to fat (weight), and it's unfortunately not really that simple in real life.

I know, but that’s probably as specific as is useful for a cyclist’s purposes. Tracking day-to-day weight fluctuations is inherently pointless. If I notice acute changes in weight after a very long ride, it’ll generally be 36-48 hours later. Trends/moving averages are what I care about.

[Singular]

Maybe to clarify, another reason I don't look at water replenished is that the weight I am regarding is the total system weight, rider + bike + everything he carries.

So I want to know how much the system weight of a rider goes down during a ride, to calculate the power needed for a hillclimb for example.

edit: regarding bikecalculator, useful. thanks, if the mass of say 1000 calories is really significantly less than 0.1 kg, I will not consider it.
I am not calculating static, averaged efforts though but the whole ride based on GPX data.

Well, here's the deal - it is indeed about 100grams if it was pure lard that was taken off your body, but if it's only glycogen it is about 200-250 grams. Expect each gram of glycogen to bring about 3-4 times its weight in fluid, making a change in weight that is much larger (it can literally be 10x in this case).

[xkcd]

[Well, here's the deal - it is indeed about 100grams if it was pure lard that was taken off your body, but if it's only glycogen it is about 200-250 grams. Expect each gram of glycogen to bring about 3-4 times its weight in fluid, making a change in weight that is much larger (it can literally be 10x in this case).

Thanks, I really thought it was easier to quantify it.

On the other hand, I rode today and got a number for me! I lost 1.8 kg in 2.5 hours (0.72 kg/h), which is close to exactly 1% system weight! It was 13 C and I used up about 2000 calories.

When I implemented this in my algorithm, the power numbers did eventually change.
From 201 to 200 watts. LOL

Anyway, I think I will use a conservative number (0.8%) per hour, as I rather have it in than not. Just because I can.

[TobinHatesYou]

On the other hand, I rode today and got a number for me! I lost 1.8 kg in 2.5 hours (0.72 kg/h), which is close to exactly 1% system weight! It was 13 C and I used up about 2000 calories.

Hydrate better.

Also how are you determining your kJ/kcal burn? Do you actually have a power meter?

[xkcd]

Well I don't, but I can say with confidence that my calculated power is close enough to say such an estimation.

I drank about one liter. My body weight loss was therefore about 0.8 kilograms, but since I emptied my water bottles in the process, the weight I had to move was 1.8 kg.

[Singular]

Did you weight yourself dressed (as a lot of the weight, as water, will stay in your clothes)?

As mentioned above, it's a bit too much guesstimates to make this viable.

[xkcd]

I weighed myself going out of the door and coming back in, with the bike, and everything I carried.

At this point, it only has to be viable for myself. I think it is more accurate than not considering it to be honest.