...According to BMI - new home page stuff
I would like to add some arithmetic on this! I had a test years ago when i was 158 pounds (6ft 1). I was in pretty good form and had done an 8m run at close to 7 min mile pace that morning. The test was putting some electodes on various parts of my body inc. ankles and comoing up with 10.8% fat and 65% water. The range for water was said to be 55-65% water, so i was right on the upper limit.
65% of 158 is 103 pounds, but if one was at 55% it would be 87 pounds so you would have lost 16 pounds. For my weight i would then be 142 pounds, this would improve my times i suspect! If 76% of my weight is fat and water then 24% must be down to bone density and muscle. I would argue that i couldn't go down to less than 7% fat, so where could i lose weight beyond 6 pounds (i am at the same weight now). And yet i did get down to 152 pounds last year when i came back from India. No, i don't think it was fat loss- more likely to be water! I would add that it doesn't mean i was dehydrated, only that my water level was down on what it had been.
In 1975 when i broke my jaw i was 133 pounds momentarily, i have a picture of myself. You wouldn't want to be this thin, so its muscle and fat i lost. One contributor said that they were this light while running 40 mins for 10k, this is just incredible! But i wonder if the reason older people lose weight is down to bone density rather than anything else. Back to the 59 kg person who was 184 cm tall, it may be the biscuits they are eating that is causing the light weight but remember that with a mimimal food intake, which is almost certainly what they have, they are not leaving much room for actual meals. The author of the British Cycle Federation coaching manual stated that empty calories should be avoided. He was right!
As i said my weight is now the same as it was that day. I was 39 then, am now 51. But ,where have i lost weight? Water, bone density, fat or muscle. Or are all my levels the same. It seems that if any of these figures are less than othe other ones may be more. I have a feeling that my fat level will be up marginally(maybe 2%- this amounts to just 3 pounds). This will mean i have lost either muscle or bone density! In 1979 i was 170 pounds as a racing cyclist, i would put it down to more muscle with some increase in fat but not much. If i remember rightly i was 32 inch waist but now am no more than 1/2 inch less!
So tell me are some of these satements flawed in some way or am i right. Does bone density go down with age or is it minimal in terms of overall weight for older people.
older people lose muscle mass very quickly when they are ill
and the "water" thing ..thats also blood, lymph and other fluids not just water that is held in tissues ("water" retention) as well as a rather large part of the brain (85%?)
actually - going back to the muscle thing - i wonder if one of the reasons average BMI is increasing is that as well as getting fatter people are getting heavier because of more muscle mass ?
We know that better quality and quantity of food available has meant height has increased over the last couple of generations but if you look at pictures of people post war (after rationing and food shortages) then there were a lot of people who looked underweight/skinny by comparison to recent years (im not talking about comparing to obviously "overweight" people -just people who would be considered "normal" weight) -perhaps our plentiful supplies mean that we are getting bigger and heavier and not just fatter ?
i know nothing really ..its all just specualtion !
Fatter people need more muscle to support their weight, so a small proportion of their excess weight is muscle. And muscle mass decreases with age (i.e. for the same weight, the proportion of fat to muscle increases as one gets older) which is a good reason to do resistance training to reduce this effect. When fat people lose weight, they also lose a little of the muscle mass which is not required anymore. By the way, there is plenty of water in muscle (blood, muscle cells etc) so that has to be factored in when doing calculations. Bone weight doesn't decrease significantly with age unless there is severe osteoporosis.
And fatter people have a higher metabolic rate, i.e. they burn more calories at rest and during exercise than thin people - despite what many people think. See www.bbc.co.uk/truthaboutfood and click on 'slim', then 'metabolism and weight' to see a common fallacy debunked (i.e. that 'naturally slim people' eat more than fat people yet remain slim). The truth is that overweight people eat more than slim people, often without realising it.
The world has grown fatter since the last world war, due to increased calorie intake and decreased activity - but most of our increased calories are junk calories. Many obese people are malnourished because most of their calorie intake is from junk food.
Agree with all the posters who have questionned the relevance of BMI. We're all runners and exercise has a significant effect on health risks. Someone with a 'normal' BMI who doesn't exercise carries greater health risks than someone who is 'fat and fit'. I'm fitter than ever but BMI 27ish. I've still got fat to lose but thats only because I want to shave seconds off the shorter distances (and look 'trim' I suppose)...
BMI is a generally useful risk predictor for the general population and easy to measure. But it doesn't go much beyond that.
I measure "thinner" but weigh more than I have at times (when not running so much)?!? I presume that this is the muscle weighing more than fat thing?
My BMI is 19.1 (which is in the healthy range) - but my size 8 clothes are kind of baggy... even though I have at times been half a stone lighter? That article on speed makes it seem like if I weighed less then I would be faster in races - but I think I'd have to start wearing childrens clothing.
I run around 30 miles a week at present, but not training for any particular event. Thinking about my first half marathon (only done 10K or 10 mile races up until now). Not sure what my optimum weight is to stay healthy and run well. I guess anything down to a BMI of 18.5 is ok? Or would that make me too think cos of having very little body fat???
You'll only find your optimum weight by trial and error. If your periods cease, you're almost certainly underweight or have insufficient fat. Obviously if you're an elite runner, you'll want to be as light as possible while remaining healthy - all elite distance runners are very slim, with BMI around 18.5.
The ideal is to make all your calories count - i.e. no junk calories, so that you maximise your nutritional intake. Only those training immense volumes will have to eat a lot of sugary stuff to get sufficient calories in easily digestible form.
I measure 31.5 / 23.5 / 33.5 inches... but my BMI is (just) inside "normal" - and above what some running places think is "optimal"...
I've read a lot recently that waist to hip ratio is the best indicator of general health (below 0.8 for women and below 0.95 for men). Makes sense to me... my BMI is a very "normal" 22.3 but until i started running I was only just below the line for a healthy waist size. Since I started running my weight has barely changed but the inches are falling off my waist...... is that any help to anyone?
Sports Nutritionist in training here. I've spent more time than I care to think about being lectured about the limitations of BMI.
In essence BMI is an indicator of body weight not fatness and as others have said it is not a sensitive indicator of fatness in people who are active/athletic etc. It has its limitations in the "normal population" as well. You can quite easily be in the normal BMI range and have a high body fat percentage and equally you can be in the overweight or obese BMI category and have a low or normal body fat measurement. Then of course what really matters is where that fat is deposited.
Calipers and the bio impediance scales (like the Tanita ones) also have their limitations. Calipers need a skilled person using to produce good results and they have a relatively large margin of error. And the bio impediance scales need proper hydration to give a good result and can also over estimate body fat in athletic people (if the wrong set of equations are used).
Waist measurement, waist to height ratio (less than 0.5) or waist to hip ratio are all good indicators of abdominal fatness (which is the fat that carries the health risks) that are easily measured. As long as you measuring at your natural waist which isn't always where your waistband falls .
But BMI is a very insensitive indicator and basically not worth the huge amount of importance that people have attached to it over recent years.
Using the Arnie example, isn't it a case that a persons heart can only support so much weight, and therefore, even if your whole body is lean muscle, by virtue of the fact that you're overweight it's putting a strain on your heart?
This is how i interpret the bmi scale, at least for people who are overweight anyway. And Arnie had a heart attack didn't he? But agreed it can't possibly tell you how much fat you carry.
ValleyGirl- yay for someone saying how useless BMI is! And yay for all the other people on the thread dissing BMI too.
I remember a few years ago a couple of my friends were convinced weight was a good measure of healthiness and although I weighed the same as one girl, she was a good 1-2 dress sizes larger than me- because I exercised a whole lot more, I had a lot more in the way of muscle mass.
Saying that, I've now gained a bit (lot?) of excess flab in the middle, really want to lose that as it'll look better and who knows, if I combine it with my increased training I might even hit 9 minute miles.... (I know that's slow for some people but I'd consider it fast for me!).
Not neccessarily - its is probably the widest bit! it is over the navel - relaxed but not breathing in and pulling belly in
lots of people -well men - wear their trousers under their natural waist -particularly if they have a large overhang - so think their waist is say 34 when actually it may be 4-6 " more when measured properly
waist circumference measurement or hip to waist ratio is about identifying people who have more abdominal fat (apple shape as opposed to pear shape) because this is thought to increase the risk of heart disease and diabetes and is now used in conjunction with BMI to assess whether someone is within a healthy weight range - a bit of common sense observation will determine whether someones BMI is significant or not !
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