Nice, it's good to see this laid out! I'll need to start using the term 'glycogen stores' rather than 'water weight' (especially since that's more useful as a term for fluid retention).
so what you're really saying (and what authoritarian regimes want to hide from us) is that we're all, on average, equipped to sustain a 2 month hunger strike?
More seriously, could this be the reason why "all diets work" short term but very few hold long term? The implications of an initial 2000 calorie deficit leading to a 2.25kg weight loss is that running even a small deficit for a short period of time will lead to short-term, impressive gains on the scale, but will be reverted just as fast.
Also, do you think this is affected by what you eat? I assume if you eat less sugar, the body has a harder time making glycogen. Actually, it's perhaps the whole point of the keto diet: keeping your glycogen forever low so that your body can't use that juicy buffer and is forced to tap into fat stores?
I might be wrong about this, but don't the glycogen stores in your muscles only get depleted if they're used to power those specific muscles? So if you don't use your quads during your fast, the glycogen in your quads won't get used up. Thus, your weight loss pattern while fasting will depend on both your amount of exercise and which muscles you exercise.
I recently learned that 1 lb of weight is not 3500 calories as many people believe, but is variable depending on a lot of factors. I am guessing a lot of what you have here plays into that. Very interesting stuff.
This is very nicely laid out, thank you! I hadn't known about the glycogen explicitly before, and the notion fills a lot of gaps for me. Particularly why I can drop 10 lbs in a week of hard labor, or 6 lbs from a day of food poisoning. That always struck me as odd.
A couple years ago I did a low-carb diet and did experience this quick drop in water weight. I’m not sure how much of it is due to glycogen depletion as you describe here, versus the loss of water that happens when you enter ketosis with a loss of sodium, and the attendant flushing out of water from the kidneys to maintain sodium balance in the blood.
Nitpick: refering to kcal as "calories" means favoring a term with two interpretations varying by three orders of magnitude over a shorter, unambiguous, SI-compatible term. In the EU, the food energy content is given both in kJ/100g and kcal/100g, and people generally can interpret them. Following your SI (imperial) unit scheme for weight, stating the energy as "~8000kJ (~2000 Calories)" or "2000kcal (~2000 Calories)" might be preferable.
From my understanding, glycogen and body fat could be likened to a capacitor and a (secondary) battery. Storing glucose (electrical energy) in glycogen (a capacitor) is highly efficient, but takes a lot of weight because the storage density is low. So instead your body (an electrical car) stores its long term energy reserves in fat tissue (a battery), which has a much lower energy conversion efficiency, but a much higher energy density.
Which leaves the question what the efficiencies of both methods of energy storage are. For glycogen, I would assume that the efficiency is probably high, polymerizing/depolymerizing glucose molecules without changing their inner structure does not sound costly. 70-95%, perhaps?
For fat, it likely depends on the starting point. Turning food fats into body fats does not feel to be terrible hard. Turning carbohydrates into fats seems much more difficult. I would assume that this is overall less effective. I would guess perhaps 40-80% of the energy of glucose can be transformed into fat (with a part of the waste energy possibly being captured in NADH or ATP or whatever weird non-SI currencies cells use for energy).
Nice, it's good to see this laid out! I'll need to start using the term 'glycogen stores' rather than 'water weight' (especially since that's more useful as a term for fluid retention).
so what you're really saying (and what authoritarian regimes want to hide from us) is that we're all, on average, equipped to sustain a 2 month hunger strike?
More seriously, could this be the reason why "all diets work" short term but very few hold long term? The implications of an initial 2000 calorie deficit leading to a 2.25kg weight loss is that running even a small deficit for a short period of time will lead to short-term, impressive gains on the scale, but will be reverted just as fast.
Also, do you think this is affected by what you eat? I assume if you eat less sugar, the body has a harder time making glycogen. Actually, it's perhaps the whole point of the keto diet: keeping your glycogen forever low so that your body can't use that juicy buffer and is forced to tap into fat stores?
I might be wrong about this, but don't the glycogen stores in your muscles only get depleted if they're used to power those specific muscles? So if you don't use your quads during your fast, the glycogen in your quads won't get used up. Thus, your weight loss pattern while fasting will depend on both your amount of exercise and which muscles you exercise.
Good writeup! I talk about the more practical applications of this in dieting here: https://exfatloss.substack.com/p/water-weight-temporary-fluctuations
This was great.
I recently learned that 1 lb of weight is not 3500 calories as many people believe, but is variable depending on a lot of factors. I am guessing a lot of what you have here plays into that. Very interesting stuff.
This is very nicely laid out, thank you! I hadn't known about the glycogen explicitly before, and the notion fills a lot of gaps for me. Particularly why I can drop 10 lbs in a week of hard labor, or 6 lbs from a day of food poisoning. That always struck me as odd.
What about muscle mass? Is that included in the “body fat” category?
A couple years ago I did a low-carb diet and did experience this quick drop in water weight. I’m not sure how much of it is due to glycogen depletion as you describe here, versus the loss of water that happens when you enter ketosis with a loss of sodium, and the attendant flushing out of water from the kidneys to maintain sodium balance in the blood.
Nitpick: refering to kcal as "calories" means favoring a term with two interpretations varying by three orders of magnitude over a shorter, unambiguous, SI-compatible term. In the EU, the food energy content is given both in kJ/100g and kcal/100g, and people generally can interpret them. Following your SI (imperial) unit scheme for weight, stating the energy as "~8000kJ (~2000 Calories)" or "2000kcal (~2000 Calories)" might be preferable.
From my understanding, glycogen and body fat could be likened to a capacitor and a (secondary) battery. Storing glucose (electrical energy) in glycogen (a capacitor) is highly efficient, but takes a lot of weight because the storage density is low. So instead your body (an electrical car) stores its long term energy reserves in fat tissue (a battery), which has a much lower energy conversion efficiency, but a much higher energy density.
Which leaves the question what the efficiencies of both methods of energy storage are. For glycogen, I would assume that the efficiency is probably high, polymerizing/depolymerizing glucose molecules without changing their inner structure does not sound costly. 70-95%, perhaps?
For fat, it likely depends on the starting point. Turning food fats into body fats does not feel to be terrible hard. Turning carbohydrates into fats seems much more difficult. I would assume that this is overall less effective. I would guess perhaps 40-80% of the energy of glucose can be transformed into fat (with a part of the waste energy possibly being captured in NADH or ATP or whatever weird non-SI currencies cells use for energy).