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> At this point, I knew I needed to eat 1000 calories/day less than I burned. I used this calculator to identify that, as a sedentary person, I burned about 245

> At this point, I knew I needed to eat 1000 calories/day less than I burned. I used this calculator to identify that, as a sedentary person, I burned about 2450 calories/day. I've seen plenty of calculators like this around the web, and even seen calculators that estimate how many pounds per time you'll gain/lose depending on the activity level and food intake, but they never show their formulae or cite sources that give formulae. Does anyone know of reasonable sources for that? I'd love to have a probabilistic model of "a group of people who eat X calories per day and weigh Y with Z body fat percentage, will weigh (in distribution) A +/- B with C +/- D body fat after T time period" or similar, but nutrition info is never written in that detail, even though these calculators must come from somewhere.

nradov 3y ago
On an individual basis it doesn't really matter. Those calculators can only ever provide a rough estimate as a starting point. People who want to lose weight will have to weigh themselves on at least a weekly basis and then titrate their calorie intake up or down to hit their target. If you do want to know how many calories you burn as a sedentary person, then just go get a resting metabolic rate (RMR) test. This is a cheap, non-invasive test where they measure how much oxygen you metabolize and use that to directly calculate baseline daily calorie consumption. Any physical activity will then be additive to that baseline. Effects on body fat or body composition vary tremendously based on dietary macronutrients, exercise, genetics, gut microbiome, and other factors so I don't think we know enough to construct an accurate probabilistic model of that. In general, to avoid loss of muscle tissue the recommendation is to maintain a high protein intake and do resistance (weight) training.
jitl 3y ago
Really all the complicated algorithm here is estimating basal metabolic rate - the "amount of energy expended while at rest in a neutrally temperate environment, and in a post-absorptive state (meaning that the digestive system is inactive, which requires about 12 hours of fasting)". That quote comes from the BMR calculator I use, which also explains clearly the different estimation methods and their variables [1]. Their calculator takes sex, weight, height, age, and body fat percent. Other than your BMR, you can compute (weight loss / day) with 3 more variables, the activity calories per day (just added to your BMR), the number of calories in a pound of fat (most round to 3500kcal because it makes mental math easier), and the calorie intake per day. Then: NET_DAILY_KCAL = (BMR + ACTIVE_CALS) - INTAKE WEIGHT_CHANGE_RATE = NET_DAILY_KCAL * FAT_PER_KCAL [1]: https://www.calculator.net/bmr-calculator.html https://www.calculator.net/bmr-calculator.html
switch007 3y ago
https://www.calculator.net/tdee-calculator.html https://www.calculator.net/tdee-calculator.html Let’s you choose between two named formulae that you can further research.
bsder 3y ago
1000 calories per day deficit (kcal for those using a sane system) is HARD. More power to him for pulling it off, but most people's bodies will fight them really badly with that kind of deficit. After two weeks on that kind of caloric deficit I get really angry and grouchy all the time. I have done it, but people around me definitely made comments when I went back to "normal" as to how much nicer I was.

nradov 3y ago

On an individual basis it doesn't really matter. Those calculators can only ever provide a rough estimate as a starting point. People who want to lose weight will have to weigh themselves on at least a weekly basis and then titrate their calorie intake up or down to hit their target. If you do want to know how many calories you burn as a sedentary person, then just go get a resting metabolic rate (RMR) test. This is a cheap, non-invasive test where they measure how much oxygen you metabolize and use that to directly calculate baseline daily calorie consumption. Any physical activity will then be additive to that baseline. Effects on body fat or body composition vary tremendously based on dietary macronutrients, exercise, genetics, gut microbiome, and other factors so I don't think we know enough to construct an accurate probabilistic model of that. In general, to avoid loss of muscle tissue the recommendation is to maintain a high protein intake and do resistance (weight) training.

jitl 3y ago

Really all the complicated algorithm here is estimating basal metabolic rate - the "amount of energy expended while at rest in a neutrally temperate environment, and in a post-absorptive state (meaning that the digestive system is inactive, which requires about 12 hours of fasting)". That quote comes from the BMR calculator I use, which also explains clearly the different estimation methods and their variables [1]. Their calculator takes sex, weight, height, age, and body fat percent. Other than your BMR, you can compute (weight loss / day) with 3 more variables, the activity calories per day (just added to your BMR), the number of calories in a pound of fat (most round to 3500kcal because it makes mental math easier), and the calorie intake per day. Then: NET_DAILY_KCAL = (BMR + ACTIVE_CALS) - INTAKE WEIGHT_CHANGE_RATE = NET_DAILY_KCAL * FAT_PER_KCAL [1]: https://www.calculator.net/bmr-calculator.html https://www.calculator.net/bmr-calculator.html

switch007 3y ago

https://www.calculator.net/tdee-calculator.html https://www.calculator.net/tdee-calculator.html Let’s you choose between two named formulae that you can further research.

bsder 3y ago

1000 calories per day deficit (kcal for those using a sane system) is HARD. More power to him for pulling it off, but most people's bodies will fight them really badly with that kind of deficit. After two weeks on that kind of caloric deficit I get really angry and grouchy all the time. I have done it, but people around me definitely made comments when I went back to "normal" as to how much nicer I was.