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A "calories in vs calories out" mindset makes the (incorrect) assumption that for a given unit of food, all persons will absorb the exact same quantity of calor

A "calories in vs calories out" mindset makes the (incorrect) assumption that for a given unit of food, all persons will absorb the exact same quantity of calories from it. Our digestive systems do not extract 10% of available energy from all consumed food, and the amount we do extract varies based on a number of different factors including microbiome, expression of certain hormones (e.g. insulin), etc. The "magic" that people refer to with keto, etc is that some things can have effects that cause our bodies to absorb less of the calories that were put into our mouths. This is one of many reasons why some people lose weight more readily than others given identical diets and exercise regimens.

mckirk 5y ago
Thanks for mentioning this effect; I sadly seem to primarily have friends in the 'can't gain weight no matter what they eat'-group, and if I try to keep up with their eating-habits, I gain two pounds a week. And yes, I do exercise a fair amount and all that, but I also seem to be quite efficient at extracting energy from food. I tend to joke that at least I'll survive longer after the apocalypse.
- scottlamb 5y ago
  Unless your friends have tape-worms, are suffering from untreated Celiac disease, or the like, [1] I doubt you're significantly more efficient at absorbing food energy than they are. It's a myth that people get overweight from being better than others at extracting energy from food. In a peer comment to yours, I gave a citation to that effect. I think basal metabolic rate can vary significantly. This might explain what you're observing in a more biologically plausible way. My (imperfect) understanding is that it's partly genetics and partly in your control via strength training. But I think you're doing yourself a disservice if you're discounting too easily the possibility that you're not comparing your eating and exercise with theirs accurately. How confident are you that you're actually eating no more calories than they are in a typical week? You might see them eat a huge amount when you're together, but maybe that's their "cheat" day, maybe they don't snack or drink alcohol as much as you do, etc. I think a lot of people are fooling themselves when comparing to others. [1] not a recommended weight loss plan; side effects can include stress fractures, scurvy, IBS, and on and on.
scottlamb 5y ago
> Our digestive systems do not extract 10% of available energy from all consumed food, and the amount we do extract varies based on a number of different factors including microbiome, expression of certain hormones (e.g. insulin), etc. Do you have a citation for this? Here's one saying almost the opposite: > Carbohydrates, protein, fats, and alcohol—the dietary macrocomponents—are the sources of energy in the diet. Under normal circumstances, more than 95% of this food energy is digested and absorbed from the gastrointestinal tract to provide the body's energy needs. Studies of normal and overweight subjects have not shown any significant differences in the proportion of food energy absorbed. In some underweight subjects, however, malabsorption of nutrients is an important factor. https://www.ncbi.nlm.nih.gov/books/NBK218769/ https://www.ncbi.nlm.nih.gov/books/NBK218769/
Spivak 5y ago
People doing CICO don't assume that all which is why "your number" where you lose weight varies person to person, diet to diet, and changes over time. CICO just says that a number exists where you'll lose weight.
dogma1138 5y ago
W/E marginal differences exist outside of specific health conditions they are less than negligible. People do extract pretty much the same amount of effective calories form identical foods, it’s basic evolution as more efficient eaters would’ve outcompeted the rest a long time ago. So unless you have celiacs, an onset of diabetes or some belly buddies you aren’t going to be absorbing less calories than someone else.

mckirk 5y ago

Thanks for mentioning this effect; I sadly seem to primarily have friends in the 'can't gain weight no matter what they eat'-group, and if I try to keep up with their eating-habits, I gain two pounds a week. And yes, I do exercise a fair amount and all that, but I also seem to be quite efficient at extracting energy from food. I tend to joke that at least I'll survive longer after the apocalypse.

scottlamb 5y ago
Unless your friends have tape-worms, are suffering from untreated Celiac disease, or the like, [1] I doubt you're significantly more efficient at absorbing food energy than they are. It's a myth that people get overweight from being better than others at extracting energy from food. In a peer comment to yours, I gave a citation to that effect. I think basal metabolic rate can vary significantly. This might explain what you're observing in a more biologically plausible way. My (imperfect) understanding is that it's partly genetics and partly in your control via strength training. But I think you're doing yourself a disservice if you're discounting too easily the possibility that you're not comparing your eating and exercise with theirs accurately. How confident are you that you're actually eating no more calories than they are in a typical week? You might see them eat a huge amount when you're together, but maybe that's their "cheat" day, maybe they don't snack or drink alcohol as much as you do, etc. I think a lot of people are fooling themselves when comparing to others. [1] not a recommended weight loss plan; side effects can include stress fractures, scurvy, IBS, and on and on.

scottlamb 5y ago

> Our digestive systems do not extract 10% of available energy from all consumed food, and the amount we do extract varies based on a number of different factors including microbiome, expression of certain hormones (e.g. insulin), etc. Do you have a citation for this? Here's one saying almost the opposite: > Carbohydrates, protein, fats, and alcohol—the dietary macrocomponents—are the sources of energy in the diet. Under normal circumstances, more than 95% of this food energy is digested and absorbed from the gastrointestinal tract to provide the body's energy needs. Studies of normal and overweight subjects have not shown any significant differences in the proportion of food energy absorbed. In some underweight subjects, however, malabsorption of nutrients is an important factor. https://www.ncbi.nlm.nih.gov/books/NBK218769/ https://www.ncbi.nlm.nih.gov/books/NBK218769/

Spivak 5y ago

People doing CICO don't assume that all which is why "your number" where you lose weight varies person to person, diet to diet, and changes over time. CICO just says that a number exists where you'll lose weight.

dogma1138 5y ago

W/E marginal differences exist outside of specific health conditions they are less than negligible. People do extract pretty much the same amount of effective calories form identical foods, it’s basic evolution as more efficient eaters would’ve outcompeted the rest a long time ago. So unless you have celiacs, an onset of diabetes or some belly buddies you aren’t going to be absorbing less calories than someone else.