How much fat does our body actually have?

Workout4Health
Workout4Health Posts: 447 Member
in Health and Weight Loss
This is a general question. I may sound naive when asking this, but I'm hoping some find it a little insightful and I'm just speculating. I have read that our bodies are 60 percent water. So if that's true, lets use this as an example. A 200 pound man who wants to lose 30 pounds. If our bodies are 60 percent water, he'd weight only 80 pounds if you took away all the water. So out of those 80 pounds, a certain amount of that is going to be muscle. Actually let's say he was 25 percent fat. Wouldn't that mean 60 pounds of muscle and 20 pounds of fat? So it seems to me that if water really covers the majority of our weight, then we really don't have as much body fat as we think we do. Maybe I'm crazy. But lets take one pound of fat. That's about 35 miles of walking. Most people don't walk that much in a day. Heck, most people don't walk that much in a week. But then let's say they lose half of their calories from their diet. That would still mean 17.5 miles they'd have to cover, even if they ate at a caloric deficit. So to lose 10 pounds, that would be 175 miles, and 20 pounds would be about 350 miles, even when eating at a caloric deficit. Something just doesn't seem to add up. I don't think people are really walking 35 miles just to lose one pound of body weight. Could it mean that the majority of our weight loss actually is really water? (Given that 60 percent of our body is water.) I mean how in the world are people losing 10 pounds in a month like it's nothing, when that's the equivalent of walking or jogging about 350 miles? Most people aren't dieting THAT heavy or putting THAT much time in cardio.

Replies

  • AllOutof_Bubblegum
    AllOutof_Bubblegum Posts: 3,646 Member
    Fat cells contain a lot of water, like all other cells. so when they say our bodies are 60% water, that's including fat.
  • henryrohwer
    henryrohwer Posts: 2
    The Wikipedia article on body fat has a section where they discuss an electrical resistance meter that might help to understand this from an electrical point of view. It says:

    "A body fat meter is a widely available tool used to measure the percentage of fat in the human body. Different meters use various methods to determine the body fat to weight ratio. They tend to under-read body fat percentage.[56]

    "In contrast with clinical tools, one relatively inexpensive type of body fat meter uses the principle of bioelectrical impedance analysis (BIA) in order to determine an individual's body fat percentage. To achieve this, the meter passes a small, harmless, electric current through the body and measures the resistance, then uses information on the person's weight, height, age, and sex to calculate an approximate value for the person's body fat percentage. The calculation measures the total volume of water in the body (lean tissue and muscle contain a higher percentage of water than fat), and estimates the percentage of fat based on this information. The result can fluctuate several percentage points depending on what has been eaten and how much water has been drunk before the analysis."

    Personally, it looks like there is still variation about this, and I like to just pinch an inch or two at the waist or other obvious areas to estimate the volume of fat in those spots. Then, if you lose like 10 lbs of total weight, measure again, and you can see how much of the fat was lost. There is another way to measure fat by floating in a tank of water and determining the buoyancy, but that isn't 100% sure either. Interesting question, though. Thanks for posting it.
  • michikade
    michikade Posts: 313 Member
    The majority of a person's body is water because the largest component of the fluid in plasma in blood, lymph, the cytoplasm in cells, extracellular fluids, etc is water. A fluid, by definition, is water with substances dissolved in it, and those substances are electrolytes, plasma proteins, glucose, etc etc etc (depending on the location and application of the fluid will determine the solutes).

    Fat, on the other hand, is a different substance chemically than water but when fat is broken down, one of the main chemical components it breaks down into is - you guessed it - H2O (the other is CO2).

    When they say a person is 60% water, they're talking about an average adult male. The percentage of water in a person varies by age, gender, height, weight and adiposity (body composition). The average adult female is closer to 55% water because females have more adipose tissue (fat tissue) than males do by nature, and adipose tissue contains less water than other body tissues. The very obese can be as low as 45% water. For interest, newborns are closer to 75% water.
  • reydoog
    reydoog Posts: 1 Member
    Taking a couple of readings from my scales may help to illustrate the numbers here.

    Two weeks ago my scales said that I weighed 187.2lb with 31.2% body fat and 50.2% water. Multiplying my total weight by these percentages meant that I had 94lb of water sloshing about inside of me and I was carrying 58.4lb of fat

    This morning my scales said that I weighed 183.4lb with 30% body fat and 51.2% water. I thought my body water was going up but when I do the sums I see that I am now 93.9lb of water (so essentially the same) and 55lb of fat.

    It looks like as I have lost 3.4lb of fat my water percentage has gone up even though the total amount of fluid in my body hasn't changed.

    To answer the original question I am about 55lb of fat at the moment - this gives me a BMI of about 28 (so overweight). If I could lose about half (i.e. two stone) of fat without losing any muscle and keeping everything else the same I would have 27lb of fat and weigh 155.4lb. This would give me a BMI of 23.6 and a body fat % of about 17% which would then put me in the normal range. At this weight to have 94lb of water (so staying the same) my water percentage would be 60.5% which would also put me in the normal range.

    At the moment by % fat is higher than normal and my % water is lower than normal but losing fat will fix both of these things!

    Hope that helps!
  • skinnyinnotime
    skinnyinnotime Posts: 4,078 Member
    This has also crossed my mind, but haven't looked into it like you have. Very interesting point.
  • JosieRawr
    JosieRawr Posts: 788 Member
    The majority of a person's body is water because the largest component of the fluid in plasma in blood, lymph, the cytoplasm in cells, extracellular fluids, etc is water. A fluid, by definition, is water with substances dissolved in it, and those substances are electrolytes, plasma proteins, glucose, etc etc etc (depending on the location and application of the fluid will determine the solutes).


    quoting this because in my mind it does a good job of illustrating that water is a part of the body, not something that's just poured in on top ;)

    200lb man at 25% fat has 50 pounds of fat.
    You cannot remove the water from the equation because it is a part of the body. The two ratios do not interact in that way. If you were doing a pie chart the water would overlap from body fluids to muscle to connective tissues(Etc), it would not be off by itself.

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