1 00:00:03,187 --> 00:00:07,704 So let's talk about body mass index (BMI). 2 00:00:07,704 --> 00:00:15,903 This is a term that's often discussed and so let's first figure out how it's calculated - how do we figure this out? 3 00:00:15,903 --> 00:00:23,719 So, if you have a little stick person, what you could do is have them step on a scale. 4 00:00:23,719 --> 00:00:27,754 And you could get their weight. So, the first thing you need is their weight. 5 00:00:27,754 --> 00:00:33,237 And then you go on and you ask them if they would mind if you would take their measurement of height. 6 00:00:33,237 --> 00:00:36,453 And so you get their "H" or height. 7 00:00:36,453 --> 00:00:44,052 And a BMI is basically just taking those two numbers and using them in a little equation 8 00:00:44,052 --> 00:00:49,519 where you take the weight divided by the height squared. 9 00:00:49,519 --> 00:00:51,986 Very simple, right? 10 00:00:51,986 --> 00:00:55,104 So now, let me calculate my BMI. 11 00:00:55,104 --> 00:00:57,204 But before I do that, I have to tell you one more thing 12 00:00:57,204 --> 00:01:03,220 Which is that, the weight, this is in kilograms (kg) 13 00:01:03,220 --> 00:01:08,136 and the height is actually in meters squared. 14 00:01:08,136 --> 00:01:11,038 So, when I was actually figuring out my own height and weight 15 00:01:11,038 --> 00:01:13,253 I realized the problem and I'll show you what that was. 16 00:01:13,253 --> 00:01:23,736 So, my weight is 160 pounds and my height is six foot, one inch. 17 00:01:23,736 --> 00:01:27,769 Which is the same as 73 inches. 18 00:01:27,769 --> 00:01:33,586 So, I would love to use this easy equation, but I have pounds and inches - I don't have kilograms and meters. 19 00:01:33,586 --> 00:01:38,387 So what do I do? Well, what I need to do first is convert over, right? 20 00:01:38,387 --> 00:01:51,419 So I can say, "Alright, well one pound equals 0.454 kilograms. So far, so good. 21 00:01:51,419 --> 00:01:59,705 And now one inch, which is pretty small, is going to be a small number relative to a meter, which is huge, right? 22 00:01:59,705 --> 00:02:09,786 And so, it is, it's 0.0254 meters." 23 00:02:09,786 --> 00:02:16,053 So, now I've got my conversions and actually, what I can do, is I can take these numbers and plug them in here 24 00:02:16,053 --> 00:02:23,602 to help me easily convert from kilos and meters over to pounds and inches - make my equation much simpler for me to use. 25 00:02:23,602 --> 00:02:34,685 So I can say, "Okay, well now how about weight in pounds and height in inches squared?" 26 00:02:34,685 --> 00:02:36,286 And I have to multiply, right? Because I have to multiply by the conversion. 27 00:02:36,286 --> 00:02:52,870 And so, I'll multiply by 0.454 divided by 0.0254 squared. 28 00:02:52,870 --> 00:02:58,720 And to make it even easier, I can actually take this whole thing, plug it into my calculator 29 00:02:58,720 --> 00:03:07,203 and it gives me the number 703. So I can say, "Okay, so really what I have here is, again, weight in pounds 30 00:03:07,203 --> 00:03:17,387 divided by height in inches squared, multiplied by 703." 31 00:03:17,387 --> 00:03:20,704 So going back now, I can finally throw in my own numbers, right? 32 00:03:20,704 --> 00:03:45,053 I can say, "Okay, so my BMI is 160 divided by 73 squared times 703." 33 00:03:45,053 --> 00:03:47,154 Let me erase that just to make it clear. 34 00:03:47,154 --> 00:03:51,270 Okay, so this math works out to 21. 35 00:03:51,270 --> 00:03:53,503 So my BMI is 21. 36 00:03:53,503 --> 00:03:56,302 Wonderful. The next question is: well, what does that mean? 37 00:03:56,302 --> 00:04:04,102 You know, if I have a BMI of 21, is that normal or is that good or how should I feel about that? 38 00:04:04,102 --> 00:04:09,620 So, if you put a scale on here starting with zero to, let's say 30 39 00:04:09,620 --> 00:04:18,219 and I have 25 here and let's say this is about 18.5 40 00:04:18,219 --> 00:04:23,453 What physicians have done is basically divide up the BMI into catergories 41 00:04:23,453 --> 00:04:30,387 and they said, "Okay, well if your BMI as an adult is somewhere between zero and 18.5 42 00:04:30,387 --> 00:04:34,852 somewhere in this range. I'm going to do it in yellow. 43 00:04:34,852 --> 00:04:44,219 Then you're underweight. I'm just going to write "under." And if you're between 18.5 and 25 44 00:04:44,219 --> 00:04:49,686 if you're in this range, you're in a very healthy range. 45 00:04:49,686 --> 00:04:53,502 And so I'll write a little smiley face for that. 46 00:04:53,502 --> 00:04:59,569 And if you're above 25, let's say 25 to 30, then you're in the overweight range. 47 00:04:59,569 --> 00:05:07,937 And finally, if you're above 30, let's say you're out here, then you're obese." 48 00:05:07,937 --> 00:05:11,753 And so that's where the word obese really comes from. 49 00:05:11,753 --> 00:05:15,053 It comes from a category of BMI. 50 00:05:15,053 --> 00:05:19,519 And so, going back to my BMI, I'm right here at 21 51 00:05:19,519 --> 00:05:24,369 and I'm doing pretty well. But, the question might come up in my head, 52 00:05:24,369 --> 00:05:30,086 "What weight would I be if I was overweight and what weight would I be if I was obese? 53 00:05:30,086 --> 00:05:34,236 How many pounds away am I from being in those categories? 54 00:05:34,236 --> 00:05:38,103 So I can go back to my equation: 55 00:05:38,103 --> 00:05:41,803 BMI equals W over H squared and I can just rearrange it 56 00:05:41,803 --> 00:05:55,320 I can say, "Well how about W equals BMI times H squared over 703, right?" 57 00:05:55,320 --> 00:06:00,587 Because that's the conversion. So if I rewrite the equation like this 58 00:06:00,587 --> 00:06:07,288 then now I can solve for my weight. I can say, "Okay, well let's say that I wanted to figure out what to do 59 00:06:07,288 --> 00:06:14,370 if I have a BMI of 25 and I know that my height probably won't change, 60 00:06:14,370 --> 00:06:22,404 I'm not going to grow anymore and 703 is the number we always have to use when we're using the conversion from 61 00:06:22,404 --> 00:06:27,188 pounds to kilos and inches to meters. So, what does that equal? 62 00:06:27,188 --> 00:06:38,370 Well, in this particular case, using 25, I can see that for me to be overweight, I would be around 190 pounds. 63 00:06:38,370 --> 00:06:43,852 190 pounds. So that's actually really, really good to know 64 00:06:43,852 --> 00:06:46,737 That's actually 30 pounds above what I am today. 65 00:06:46,737 --> 00:06:52,253 So that gives me a sense for how far away I am from being overweight 66 00:06:52,253 --> 00:06:57,610 and I can even do this for a BMI of 30. 67 00:06:57,610 --> 00:06:59,609 I can say, what about a BMI of 30? 68 00:06:59,609 --> 00:07:04,710 My current height, again, is 73 inches. That's not going to change. 69 00:07:04,710 --> 00:07:14,394 And I can do the math and find out that, in this case, my weight would be 227 pounds. 70 00:07:14,394 --> 00:07:18,394 So if I was 227 pounds, given my height, I would be considered obese.