I am 40 years old. I weigh 190 lbs. As of today, if in all my life had I consumed exactly 3500 calories less than I have, would I be about 1 lb. lighter than I am?
By that logic, if you consumed just 684,000 calories fewer, (a mere 46 less per day!) you would weigh 0 pounds.
Exactly. So then why does 3500 calories equal roughly 1 lb.?
A friend and I had this discussion while talking about alcohol consumption and the effect it had on a persons weight. We decided that 80 proof whiskey had about 65 calories per oz. If someone were to drink 3/5 of 80 proof whiskey per week they would be consuming about 5000 calories of liquor per week. If they suddenly stopped, but kept everything else the same, by the 3500 calories = 1 lb rule, they should lose about 6 lbs. in the first month. However, in practice, this isn’t the case as I know from experience.
So my question then came to why doesn’t a person weigh exactly 1 lb less if in all their lifetime that person consumed exactly 3500 calories less than they had. Needless to say, the conversation was over and we drank some more. But this got me to thinking about it today. The numbers just don’t add up.
If you had consumed more calories, the likelihood is that you would have burnt those calories as well. If you had consumed exactly 3500 calories more, and had somehow managed to have the same basal metabolic rate, burning the exact same amount of calories, then it is possible that you would weigh exactly one pound more. I’m not a doctor or other scientist, but the concept of calories in regards to the complex system of the human bodies is more like an outside boundary. The body changes what it uses based partially on what the intake is. There are varying studies, but I don’t have the background to explain them.
Generally, without splitting exact hairs over numbers… Yes…
More or less, which is why it is easy to pack on pounds. You just eat a little more than you burn every day and it adds up over a long period of time. What we tend to do in thinking about weighing less is just go, “Hmmm… I just need to create a 3500 calories deficit and I will lose a pound!”
The trouble is that a 3500 calorie deficit is hard to create over and over again, and we mentally don’t accept losing .5 lbs per month, if we actually live in reverse and just lose weight slightly much as we gain it.
Also, don’t forget that everyone has fluctuating body weights. Someone who weights 200 lbs today might weight 198.5 next month, then 199 the next, the 201 the next. We are constantly fluctuating due to overages/shortages in calories.
But I see what you are doing here: Making it seem like 3500 calories is a little thing… and over time it is… which is why so many people wind up with too many calories, and too much weight…
If you are drinking 3 fifths of whiskey in a week, you have more problems than your calorie intake …
Calorie\weight interactions are complex, because they don’t happen in isolation. We are always taking in food and fluid, breathing out moisture and CO[sub]2[/sub]. We crap, and piss and sweat. All these processes impact weight to some degree and cause our weight to fluctuate by up to 1.5kg a day…
Add alcohol consumption to that mix, and the response is even more uncertain. Alcohol consumption affects the liver, and that in turn impacts digestion. This is why heavy drinkers develop a fatty liver - normal pathways are so busy dealing with ethanol, fat just drops out into the liver because there is no capacity to process it properly. Insulin levels for managing sugars are driven high by alcohol. Normal fluid handling gets out of kilter due to the alcohol, too. Other nutrient absorption can be affected by alcohol, due to liver load and stomach irritation. So the body balance between calories and weight could well be pretty well screwed during the drinking period. And if you stop the alcohol intake, you are dropping a massive calorie source, but your body is trying to adapt to a completely different situation. In this situation, you may start getting more calories from the food you are consuming. Your water retention situation may change. Your liver may start processing locally stored fat and storing it in adipose tissue (which includes water). It may take considerably longer than a month for your body to respond to the reduction in calories. Also, stopping such a significant (to my mind, anyhow) alcohol consumption and keeping all other factors consistent (exercise, food, fluid and tobacco intake) seems to me to be very difficult, and would be the hardest thing to manage.
Si
I lost great deal of weight through very precise calorie counting and exercise, and it really showed me, for the first time, how responsive my appetite is to changes in calorie consumption and exercise level. Without very careful accounting (weighing everything you eat and keeping careful records), I think it’s virtually impossible to even know if your food consumption has changed in response to other changes.
One of the key issues that makes the original thought less useful is that heavier people actually burn more calories - it costs more energy to move, and the fat cells themselves require some upkeep. This page covers a lot of basal metabolic rate information, and claims that a rough-and-dirty calculation of 15-16 calories per lb of body weight is a good estimate.
So if you weight more, you burn more calories just doing nothing. Eating an extra 350,000 calories doesn’t make you 100 lbs heavier even though 1 lb of fat is 3500 calories. You might stabilize at 10 lbs heavier, which increased metabolism by 150 calories a day. The “missing” 315,000 calories were burned to maintain your higher weight. (At 150/day, 315,000 calories only takes 7 years, which is pretty short on a 40-year time scale).
Part of the problem too with lifetime calories is from birth up until the age of 21 or so you need a lot of calories above and beyond “maintenance” just to keep making your body bigger and bigger. That is only logical, there is nothing magical about a tiny little baby becoming a 6’4", 250 lbs man, you have to add more matter into your body throughout your childhood and teenage years than your body uses just to survive to create that excess mass that causes you to get bigger and bigger.
A starving person will never become big, and thus children who grow up starving all the time (see: North Korea) are vastly smaller than children in first world countries.
Also mind 3500 calories is how much energy is in one pound of fat. So if I went up to you and ripped one pound of pure fat out of your body and took it to a lab and basically burned it to evaluate how much energy was in it, it would be 3500 calories.
The only way you can add one pound of fat to your body is to eat 3500 calories in excess of what you use. The reason this makes absolute sense and is in fact essentially a proven law of science is that the human body cannot store energy from nowhere. If I consume 2800 calories on the dot, every single day, and my body burns 2800 calories on the dot every single day, it is impossible due to laws of thermodynamics for my body to create a storage depot of 3500 calories (the pound of fat.)
It’s like this, say I spend $500 a day and $500 a day is deposited into my checking account. I have $0 in my savings account. Assuming my daily income never changes and my daily expenditure never changes, believing a pound of fat could come from somewhere other than a surplus in income is akin to believing my savings account would magically wind up with $3500 in it some day, without me ever actually earning a surplus over my daily expenditure.
Now keep in mind that 3500 calories is the amount of energy in a pound of pure fat. Muscle I believe is about 600 calories to the pound, and obviously some of your lifetime calories had to go into growing your bones and such when you were a child.
Alcohol significantly distorts the picture.
Let us take our hypothetical man whose body uses exactly 2800 calories every single day. What you must realize is that the human body can turn much of what you eat into fat stores, the great thing is you can add on fatty tissue whether you actually consume much animal fat because your body has processes for breaking food down into a form that can be reconstituted as fat stores. This is good because otherwise humans would have troubles.
Something the human body can use for energy but cannot turn into fat stores is alcohol. So alcohol literally cannot make you fat by itself, a common misconception. If 2800 Man eats 2,000 calories in food per day and drinks 800 calories in alcohol, he will never gain weight. If he eats 2,000 calories in food and drinks 1,000 calories in alcohol, he will gain weight. Because those 1,000 calories in alcohol make his effective calorie requirement for the day 1800, and he has exceeded that by 200 in food calories, so he will pack on at a surplus rate of 200 calories a day (a lbs every 17.5 days.)
Now let’s say instead 2800 man consumes 0 calories in food and 3000 calories in alcohol every day. He will not lose weight because his body is having its energy needs met, but he will not gain at a 200 calorie/day rate because he is getting 100% of his calories from alcohol and that cannot be turned into stored energy by the human body.
My quick internet skills tell me that 1 oz of pure ethanol contains 842 kJ of energy. So to get 3,000 calories per day you would have to consume something like 14.92 oz of 100% pure ethanol.
An average non-light beer has around 150 calories for 12 ounces. At 5% ABV that means the average beer has around 505.2 kJ of energy from alcohol (120 calories.) So obviously around 30 calories are coming from something other than the alcohol content, and that is true of most forms of getting alcohol, you bring in non-alcohol calories with the alcohol itself. So from a practical perspective you would be very hard pressed to consume 3,000 calories of pure ethanol per day, although you could do it if you got your hands on 200 proof stuff. Additionally aside from the various amino acids, essential fatty acids and et cetera your body would be deprived of from such a diet, you would be subjecting it to great trauma by putting so much alcohol in your body every day and you would certainly die from such behavior in a moderately short window.
I’ve seen some end stage alcoholics and while many of them can get almost this bad, where they are ingesting denatured almost 100% pure alcohol and eating virtually no food, those periods tend to come and go and of course alcoholics at that stage of the game typically do die at some point.
Not according to Wolfram Alpha, which says a pound of pure oil is 4000 calories. Is this because we’re comparing pure fat to bodily fat, which partially consists of blood vessels and water and such? Or is there some other reason?
I have never, ever understood the whole 3500 cals = 1 lb of fat thing. What kind of fat? Adipose tissue? Triglycerides? Fatty acids?
Also, the body regulates its consumption heavily based upon energy intake, output, and hormonal factors. Frankly, if you have a net energy loss of 500 cal/day, your body will quickly adjust so that your BMR is lower.
And again, not sure where the 3500 cals = 1 lb of adipose tissue comes from. I mean, okay, let’s say that if you burn 1 lb of stearic acid in a bomb calorimeter you get 3500 cals of energy. Fine. How do you go from that to assuming human metabolism works just as efficiently as a bomb calorimeter, and that adipose tissue is burned exactly the same as stearic acid?
This and many other publications will confirm 3500 to lose a pound of fat.
However various forms of essentially pure fat do yield an energy amount of 4000/lbs (lard is about 4096 per pound), so I’m not sure why there is the 500 calorie discrepancy but if you search on MedLine (which is government ran) that is definitely the consensus number to lose a pound. So why the discrepancy I can’t figure out and I’m well out of my depth on matters of biology ( I only know a bit about the science of weight loss because I used it to lose over 60 lbs some years ago myself.)
I know that in the process of breaking down our excess food into something that can be stored inside adipocytes there is an efficiency loss, and I would assume there is an efficiency loss getting it out too. So maybe if you create a 3500 calorie deficit your body can plug that gap from stored fat but it uses up 4000 calories of “pure” fat and 500 of them are consumed/lost in the conversion so aren’t part of the weight loss numbers (that is a 100% speculative guess.) So if that is the case and you’re on a 500 deficit a day diet (about a pound per week), perhaps your body is actually breaking down 571 calories of “pure fat” to fill that 500 calorie deficit to continue operations and the 71 calories are the “transaction costs” and thus nutritionists and such do not factor them in since they would not affect dieting.
It seems the 3500 calories is based on an exclusive loss of adipose tissue constituting 87% fat. So it would be 4022 per pound of pure fat.
It was already mentioned upthread (by me) that there are things other than fat in your body and those get broken down during periods of caloric deficit as well. Body builders have always said that you cannot reduce weight without losing both muscle and fat.
Here is a paper that will probably be a lot more instructive: link
Also, your body will not “quickly adjust” so that your BMR is lower.
When I lost 60+ pounds I charted my weight every single day and careful charted my caloric intake. From those two figures using weighted averages I was able to come up to a very reliable number as to the average loss per day and how much my body was using per day. Getting 60 lbs lighter barely reduced my calories used in a day at all. I think at the end I may have been burning like 200 fewer per day than I was at 60 pounds heavier, and I was still burning 2800+ daily.
Something I learned during my weight loss is that formulas for estimated energy expenditure have traditionally been based on the assumption that your weight is lean mass. For example at my starting weight the classic formula projected I’d be burning 3500 calories a day–I wasn’t burning anywhere near that. The reason is I had over 60 lbs of fat hanging off my body and someone who is 260 lbs at 5% body fat will have a dramatically higher rate of daily energy consumption than someone who is 260 lbs at over 25% body fat (the classic obese person.)
What I have since learned is if you use measuring tape to estimate your body fat % and then estimate how many pounds of lean mass you have and then use that number to estimate your BMR and daily energy expenditure you will get a lot closer than just using your weight. It also means that as you reduce fat at a fairly high rate your BMR will not dramatically decrease simply because massive amounts of fat do not contribute to it nearly as much as you would think.
There are many other factors beyond that, of course. Most people who lose weight go from sedentary to lightly or even moderately active. That will kick up your daily energy expenditure. Mind of course the difference in BMR vs daily energy expenditure. You will always burn more than BMR by a little bit and even sedentary office workers can usually burn 1.2 x BMR. That activity factor will tend to increase if you’re serious about weight loss, even little things like walking a bit more, taking the stairs and such can kick you up to something like 1.35 or 1.4 x BMR, so you can actually increase how many calories you use per day as you lose weight.
Further, there has always been the myth of your body going into serious “starvation mode” when you diet and a resulting crash in metabolic rate. The last time we had a thread on this the only conclusive studies on it demonstrated you had to essentially be fasting for over 60 hours to see the dramatic effects of that nature.
Did you find that a 500 cal/day deficit led to exactly 1 lb fat loss/wk consistently over several months?
I don’t want to just make things up but I’m also too lazy to dig into the excel spreadsheet right before bed, but to generalize I was losing more than 500 a day and generally weeks were not large enough windows of time to be consistent. However over the full period of the diet the results of the total calories consumed subtracted from estimated caloric consumption were close enough that I was pretty confident with the method. (Plus I didn’t invent it, many people have used it to lose weight and in large part I was inspired by John Walker, founder of AutoDesk, who wrote a book you can read for free on his website about this issue.)
One of the first things I accepted was the day to day or even at arbitrary periods one week apart you can’t trust the scale enough to be meaningful, that is why I used a weighted average. Daily weight was meaningless, my weight every Sunday was meaningless. My average weight one week to the next was a bit more meaningful, but I actually used a 10 day moving average. So while the individual weigh ins were not that important, I did them to create a complete dataset and over the full course of the diet if you divide total weight loss by total number of weeks then the loss per week was right around what you would expect given my projected deficit–but again, because weight can vary from day to day based on water retention levels, undigested food, the fact that even the best efforts to weigh in under the same conditions some days you weigh in a few hours after the other or some days you forget to weigh in until after breakfast and etc so the week was a bit too small a unit of time to answer that kind of question.