wow... slow day?
That's what the breathless headline blared from the cover of the celebrity tabloid at the magazine stand. Now, I'm not much for gossip, so I didn't read the article. As a result, I am completely in the dark when it comes to what dietary strategy, supplements, exercise, or other tactics Kim employed to achieve this newsworthy outcome. I do know a few things about metabolism, however, and this gave me pause.
The implication of the headline is that the weight lost was fat, so naturally, we may ask what would one have to do in order to lose one pound of fat per day? By now, it is more or less generally accepted that one pound of fat is 3500 calories, so Kim would have had to create a daily caloric deficit in that amount. And how does one go about creating a caloric deficit? Well, everything boils down to a variation on two themes : eat less calories, or burn more of the calories that you are taking in.
Since I'm not really sure what Kim was eating, we'll explore a couple of options with respect to her diet. We're also going to need to be able to come to grips with Kim's calorie burning activities. In order to estimate what kind of activity Kim had to engage in while trying to achieve her weightloss target, we're going to use Metabolic Equivalent Units, or METs where one MET is equal to 1 calorie burned per kilogram per hour at rest ( 1 cal kg-1 h-1). Different activities have different METs levels, and they scale linearly, meaning that if you engage in a 10 MET activity, you are actually burning 10 calories per kilogram per hour, for a 13 METs activity, you will burn 13 calories per kilogram per hour and so on.
Kim is 5'3" and weighs in the vicinty of 130 lbs. or 60 kilos ( I assume ). Our interest in Kim's weight goes beyond salacious gossip, we only care about her overall mass because we want to compute her basal metabolic rate. As a bare minimum, assuming Kim is a creature of pure leisure and spends an entire day at rest ( 1 MET ) Kim burns 1 cal kg-1 h-1 x 60 kg x 24 h, or 1440 cal, well short of the 3500 calories she needed to dispose of daily in order to achieve her weight loss.
But of course, Kim hardly stays at rest the entire day. She presumably has other matters to attend to, so, we need to make some more assumptions about how Kim spends her day. Accordingly, assume that Kim sleeps for 8 hours, works for 8 hours, engages in leisure activities for 3 hours, household activities for 3 hours, and dilligently exercises for the remaining 2 hours. Armed with this, let's consider two incarnations of Kim, Extreme Kim and Reasonable Kim.
Extreme Kim (EK)
Extreme Kim is goal oriented, analytical and very focused. She knows exactly what she wants and how to get it. She is a career woman whose work day is filled with meetings and intense bouts of "getting things done!" Since she set her mind on losing that excess weight, EK has decided to forgo eating entirely for the duration. There is no better way to create a caloric deficit than by not eating!
Since EK sleeps for 8 hours a day, she consumes 1 MET per hour, per kilogram, or 1 cal kg-1h-1 x 8h x 60 kg , which is 480 calories. Now, the government has gone to the trouble of computing METs values for all the categories from the American Time Use Survey and from scanning through the "Working and Work Related" activities, it looks like those not involving heavy physical work ( i.e. management, business and financial, legal, computer and technological ) seem to range in METs from between 1.5 and 2.5 ( see the table below ). We'll split the difference and say that Kim expends 2 METs for every hour that she's working, which makes her work caloric expenditure double that of her sleeping rate, or 960 calories! Not bad, but we're 2/3 of the way through the day, and we've only gone through 1440 calories, or about 2/5 of what we need to do.
For her household activities, let's say that EK engages in rather vigorous ones, which boost her METs to 3.5! This gives her an additional calorie burn of 630, bringing the total to 2070. In terms of socializing and leisure activities, that's about 2 METs for 3 hours, or 360 calories more. The running total is now at 2430 calories, and EK is about to emabark on her 2 hour exercise regime, one which must consume the remaining 1070 calories, implying a requisite METs for that activity of at least 9 METs. The kinds of activities that Kim needs to engage in for two hours straight range from: vigorous bicycling between 14 - 15.9 mph, climbing hills at walking speed while carrying a 42+ lbs. load, or treading water at a fast vigorous pace.
Extreme Kim's problems are compounded by her choice to fast for the 10 days which is sure to impact on her ability to engage in 9 METs activities for a solid two hours, especially during the latter half of her diet and exercise program. Nevertheless, if we give her the benefit of the doubt, it is theoretically possible, albeit rather gruelling, that she pull it off. Did we mention that she is doing this daily while fasted? Extreme Kim has well and truly earned her nickname!
Reasonable Kim (RK)
RK would never go so far as to forgo eating. She has consulted with her trainer and nutritionist, and has been advised that she ought to restrict her calories to 1500 daily, maybe allocating 500 calories per breakfast, lunch, and dinner to keep things simple. In all other respects, however, her lifestyle and activities closely parallel Extreme Kim.
RK, however, whether she realizes it or not, has made a decision to trade in an extreme diet for extreme exercise. By eating 1500 calories daily, when it comes to the number of calories she needs to expend in her allotted two hours for exercise, it is the same as EK's 1070 but with the additional 1500 calories from her meals, for a whopping 2570 calories. As a result, RK needs to engage in a 21 METS activity, for two hours a day, for 10 days straight!
If you consult the compendium of physical activites tracking guide, you would find no activities listed with a 21 METs energy expenditure. The closest would be running at a 5.5 minute mile pace with a MET rating of 18. To put this in perspective, this is equivalent to running a marathon in 02:23:00. This means that Kim would be running at a pace that would have beaten all but 4 of the 45 Boston Marathon Women's Open winners since 1966. Of the 4 times that Kim would be off the race winning pace, she would never be more than 2.5 seconds behind the winner. Given that Kim would actually be running at a 21 METS pace, not 18, she would have decimated the field in any of the marathons she chose to enter. Oh yes, let's not forget, she would need to do this 10 days in succession ... that is, for 10 days straight, Kim would be running a 3/4 marathon at the race winning pace for the Boston Marathon in 2010.
Apparently, I am verbose, so I've exceeded the post 10000 character limit forcing me to yank my conclusion. You can find that on my blog, or merely wait for me to get around to posting it here.
Last edited by pklopp; 04-08-2012 at 11:10 AM. Reason: Adding a link
wow... slow day?
Did she, or didn't she?
Assuming that Kim was forthright and didn't embellish the degree of weight lost during her 10 days, and further, being familiar with the journalistic high standards to which celebrity gossip magazines are held, is it possible and likely that she lost 10 lbs.? Yes, it is. If all we're concerned with is weight, then the easiest thing to do is to manipulate the amount of water that the body is retaining. Adopt an extremely low carbohydrate diet, and you will quickly shed water weight since every gram of carbohydrate is stored in the body with an associated minimum of 2 grams of water. Some estimates put that figure as high as 4 grams of water. Incidentally, this is why your body stores energy as fat. Fat does not carry with it this extra water ballast, it is essentially a "carbohydrate concentrate!" As soon as you shed the carbohydrates, the water required to keep it soluble is shed as well ... voila ... instant weight loss. Additionally, if health is not your primary focus, diuretics and laxatives can greatly assist you in this process. This might make you look better in a bikini, but that will instantly reverse itself if you increase the relative amounts of carbs in your diet. Note that you need not change your caloric intake at all, rather merely by increasing the proportion of carbohydrates in your diet you would gain water weight.
On a personal note, about two weeks ago, I gained about 6 lbs. overnight. Given that I track my diet quite closely, and weigh myself upon waking every morning, I was quite certain that a) there had not been any dramatic change in my diet, and b) that I had indeed gone up in weight by about 6 pounds. If this were to be the result of fat accumulation due to overeating, this would represent a caloric surfeit of 21, 000 calories, or, the equivalent of eating 9 kg. of steak. Even if we were to allow for the possibility of eating while sleepwalking, there was not 9 kg. meat in the house to be eaten overnight! The only possible explanation was water weight. As it had been unseasonably warm where I live and knowing that I have seasonal allergies, I expect that I was experiencing a mild bout of edema from a histamine reaction. Not to worry, the following day, I had lost the weight!
All of this should point out the dubious value of the scale as a body recomposition tool. It is a very blunt instrument, and should not be considered the arbiter of anyone's progress. It is useful mostly because of the very low effort required to use it. However, it should be backed up with more reliable measures, such as skin fold measurements, or simply a tape measure.
Ultimately, if what interests you is fat loss, rather than an arbitrary number on a scale, then you need to realize that there is a practical limit on how much weight can be lost on any given day. Extremely rapid weight loss is not practical or sustainable over the long run. This is not a sprint, it is an endurance race. If anyone tries to tell you otherwise, they are probably selling something.