How much fat can a body burn?

hjlourenshj

Hi all, does anyone has an idea how much fat to energy a body can actually burn daily? Someone with the scientific knowledge?

erickirb

There have been studies, a lot of it has to do with the amount of fat you have on your body. someone at 8% BF% cannot burn nearly as much as someone at 30% BF%.

Hopefully someone will post a link, I have seen one posted before. but keep in mind that even then those results are ideal/most, not necessarily what you will achieve in the "real world"

jemhh

There's one study that theorizes that we can burn fat equivalent to 31 calories times the number of pounds we have in fat each day. So that would mean that if you're 150 pounds and have 20% body fat you'd have 30 pounds of fat. Multiply 30 by 31 and you get 930 calories, meaning that a 930 deficit could result in all fat burn. However, that is just one study and I've never seen it replicated and I don't put much stock in it.

That's pretty much the only thing I've seen trying to nail down the actual amount we can burn daily.

http://www.ncbi.nlm.nih.gov/pubmed/15615615

erickirb

jemhh wrote: »

There's one study that theorizes that we can burn fat equivalent to 31 calories times the number of pounds we have in fat each day. So that would mean that if you're 150 pounds and have 20% body fat you'd have 30 pounds of fat. Multiply 30 by 31 and you get 930 calories, meaning that a 930 deficit could result in all fat burn. However, that is just one study and I've never seen it replicated and I don't put much stock in it.

That's pretty much the only thing I've seen trying to nail down the actual amount we can burn daily.

http://www.ncbi.nlm.nih.gov/pubmed/15615615

This is what I was referring to. Thanks for posting

JamestheLiar

First of all, I don't have a scientific background, but I like to type so here we go.

The way I'm understanding your question is like this ... "If a person eats no food at all in a day, how much of their body's daily energy needs will come from fat stores?"

To answer those questions, it is first important to note that the body's capacity to metabolize fat is NOT unlimited. That's why most experts place a minimum safe caloric intake at around 1200 calories per day for women, and around 1400 per day for men. Your body simply cannot metabolize fat fast enough to accomodate ALL of your daily needs. For the person eating less than 1200/1400 calories, the body has a separate function to generate energy, which metabolizes lean body mass ... and no one wants that.

So, given those numbers (1200/1400) it almost seems like the "experts" are agreeing with the previous poster. The less fat you have, the lower your body's ability to metabolize fat for energy. So to calculate how many calories your body can generate from fat per day, simply figure your Daily Caloric Need (which is much higher for obese people), then subtract 1200 or 1400 depending on your gender.

I personally believe that the 1200/1400 calorie limits are way too low, so bear in mind that we're dealing with statistics and averages here.

erickirb

JamestheLiar wrote: »

First of all, I don't have a scientific background, but I like to type so here we go.

The way I'm understanding your question is like this ... "If a person eats no food at all in a day, how much of their body's daily energy needs will come from fat stores?"

To answer those questions, it is first important to note that the body's capacity to metabolize fat is NOT unlimited. That's why most experts place a minimum safe caloric intake at around 1200 calories per day for women, and around 1400 per day for men. Your body simply cannot metabolize fat fast enough to accomodate ALL of your daily needs. For the person eating less than 1200/1400 calories, the body has a separate function to generate energy, which metabolizes lean body mass ... and no one wants that.

So, given those numbers (1200/1400) it almost seems like the "experts" are agreeing with the previous poster. The less fat you have, the lower your body's ability to metabolize fat for energy. So to calculate how many calories your body can generate from fat per day, simply figure your Daily Caloric Need (which is much higher for obese people), then subtract 1200 or 1400 depending on your gender.

I personally believe that the 1200/1400 calorie limits are way too low, so bear in mind that we're dealing with statistics and averages here.

I don't believe the 1200/1500 cal limits have to do with fat metabolization but more to do with Micor nutrition (vitamins and minerals) intake, and muscle retention (Protein).

JamestheLiar

erickirb wrote: »

I don't believe the 1200/1500 cal limits have to do with fat metabolization but more to do with Micor nutrition (vitamins and minerals) intake, and muscle retention (Protein).

Hmm. You may know more than me (like I said, I just like to type), but I've never heard of anyone using overall calorie limits to dictate micro nutrition. But using the low limits in regards to muscle retention ... I fully agree.

The way I've always looked at it (and maybe a wise poster will come in and set me straight), our bodies will first metabolize fat for energy when the dietary intake is slightly low. The body won't start to break down the muscle mass (and other lean tissue) unless the caloric intake is dramatically low. Perhaps I'm wrong, though. Maybe the body actually uses both processes all the time, but the oxidation of fat just happens a bit faster.

hjlourenshj

Thanks for the info, 31 kcal per pound is a lot. I'm constantly reading on MFP and internet the 500 kcal deficit preventing lean body mass loss but didnt find a reliable scientific source claiming this. Its almost monkey see, monkey do. It seems so illogical that the body will turn on lean body mass that fast. Muscles contain much less energy then fat, the heart is a muscle and to be honest seeing people who starve are often still able to walk for a long time after most of the fat is gone. Ofcourse loss of mean mass doesnt mean 100% loss of lean mass after the 500 deficit. Is a loss of lean mass acceptable after loosing fat? Did the person getting overweight only gained fat or also muscles due to carrying more weight? Is there an equilibrium? Is a person yo-yoing and everytime crash dieting actually getting less muscles after each cycle?

In short what loss of lean mass is acceptable if you have to loose a lot of weight?