I recently talked to a woman who weighs herself 2 to 3 times daily. She admittedly calls it an obsession. I know of many others who weigh themselves at least once a day. Weight loss, or weight gain for some, is a part of measuring progress in a fitness program, but I'm seeing it used as a daily self-evaluation tool, a way to figure out if someone should feel good about themselves or downright shameful. This saddens me. No one should feel terrible all day because they weigh one more pound than they did the day before. I know that I can't change the emotional responses linked to weight fluctuation, but perhaps I can draw people away from the scale obsession with a bit of education. This post is going to take a look at why weight taken alone does not evaluate health/fitness and why daily weighing-in can be psychologically hazardous, and quite frankly, nonsensical.BMI vs. Body Fat Percentage
Because the "obesity epidemic" gets so much attention in the media, most readers will have at least heard of the Body Mass Index (BMI) Scale. BMI is calculated by dividing your weight (lbs) by your height (in) squared and multiplying by 703. For example, I am 136 pounds and 67 inches tall so my BMI is 21. BMI readings indicate whether or not your weight is in a healthy range. Below is a breakdown of BMI categories:
Under 18.5 = Underweight
18.5 - 25 = Healthy weight
25 - 30 = Overweight
30+ = Obese
BMI is simple to calculate and accurate for the general population. However, it has limitations. Being only a relationship of height to weight, it does not take into account what percentage of that weight is fat and what percentage is muscle. Athletes who have higher percentages of muscle mass are often incorrectly categorized as "overweight" based on their BMI scores. In addition, individuals with low body weight but a high body fat percentage may be incorrectly labeled as being a healthy weight.
Body fat percentage, a more accurate indicator of health than BMI, can be measured quickly and conveniently using skinfold calipers or a hand-held device known as bioelectrical impedance. Body fat categories are listed below:
Men
Under 10% = athletic
10 - 15% = lean
15 - 18% = normal
18 - 20% = above average
20 - 25% = over-fat
25+% = obese
Women
Under 17% = athletic
17 - 22% = lean
22 - 25% = normal
25 - 29% = above average
29 - 35% = over-fat
35+% = obese
For example, consider two men, Bob and Fred. They are both 5'10", 180 pounds and have BMI scores of 26, overweight by BMI standards. The two men have a trainer measure their body fat percentages using skinfold calipers and find that Bob's is at 13% while Fred's is 30%. The body fat reading distinguishes Bob to be in a "lean" range, whereas Fred would be considered obese!
I often talk about the irrelevance of weight as a number by itself, stressing the importance of body fat percentage when dealing with weight-focused clients. However, there are two other reasons to ditch the daily weigh-in.
Natural Weight Fluctuation
No one weighs the same thing every day. You could weigh yourself every hour and get a different response from the scale. We eat, we drink, we consume salty foods that draw water, some of us have menstrual cycles that bloat us and hold even more water...these things make us weigh more. But then we perspire, we expire, we urinate, we defecate...these things make us weigh less. Our metric weight is constantly rising and falling in small increments.
Think of daily weight fluctuations like seasons. In summer, we expect the temperature to be between 80 and 95 (in Philly, anyway). But if it's 79 one day, we don't go screaming about how it's fall, because it will probably be back up the next day. But if we find that the temperature drops into the 70s for 10 or 11 days in a row, we might conclude that fall is coming. We should assume that as with ups and downs in seasonal temperatures, weight too will fluctuate. Weighing ourselves month-to-month will reflect a more accurate change over time as opposed to daily weigh-ins which will only reveal natural fluctuations.
Misguided Sense of Self-Esteem
Let's say a woman wants her weight to stay below 140. She wakes up one morning and weighs herself, finding that she is 139. She may evaluate herself positively for that day saying, "I'm great. I lost weight." The next day she wakes up and weighs herself, finding that she weighs 141, promptly degrading herself and feeling worthless for having gained weight. In either case, this woman is basing her self-image on misguided logic, be it for feeling like a success or a failure at her weight-loss efforts. As mentioned above, your weight will fluctuate - it's natural. So basing self-esteem off of day-to-day weight changes is a recipe for an emotional roller coaster.
My advice is to set goals related to body fat percentage reduction, not simply weight loss. Meet with a trainer or fitness professional to take your weight, calculate your body fat percentage, and develop time appropriate goals for improving your health. Remove the daily emotional impact of scale readings but make an appointment in 4-6 weeks to assess your overall progress.
7 comments:
A few years ago I used to swim two days a week at the Univ. of PA pool (the old pool built in the 1930s, not the new one). After my swim I would always weigh myself. Sometimes the weight would be higher in the same week and it certainly put a damper on my day.
About 6 months into this routine I decided to just stop weighing myself - for in fact, I was going to the pool, and I was enjoying my time - so why potentially have a downslide just because I had a weight fluctuation.
The BMI stuff is helpful as it just makes sense... I liked the analogy to temperature as well. Currently there is no scale in my home - I plan to keep it that way.
There are no scales in my house either.
For me the best indicator of weight gain is how my clothes fit. Some days an outfit I loved myself in last week will all of a sudden make me feel like a stuffed sausage. That's when I know to cut back some. The only time I get weighed is at infrequent doctor's office visits where the scales are so old there's a 5% margin of error. So that's worthless.
I see women at the gym get on the scale buck naked every day and I wonder what they're thinking. No-one ever looks happy. How sad to be at the mercy of a scale. I just can't go there.
I hate to dwell on the problems with metrics of weight/body composition, but, well, three things, which are questions/invitations for comment, as much as they are arguments.
First, I thought measuring your body fat percentage using bioeletrical impedance was pretty unreliable because having, say, sweaty skin at the point of contact can change your conductivity, which affects the body fat percentage you would come up with using this method. Is this not true?
Second, in terms of general health, don't different people have different appropriate body fat percentages, that are affected by factors like metabolism (which depends on genetics in addition to fitness), the "frame" of your body, etc?
Third, it seems like appropriate BMI would vary radically from individual to individual. If one person has a much larger frame (skeleton) than another person of equal height, then even if those two individuals are equally fit with equal body fat percentages, the larger-framed person would have a significantly higher BMI.
In answer to Abram's first question (I only have time to post one now!), yes, bioelectrical impedance is less accurate than other types of body fat analysis. This method operates by passing an electric current through the body - if it passes through a lot of muscle mass, the current will travel faster because muscle holds more water than fat tissue, and body fat will be calculated lower. Conversely, if the current is encountering more fat tissue, it will hit resistance (less water) and body fat will be calculated lower. The obvious flaw in this method is that if a person is well hydrated, his/her body fat percentage will be underestimated and if s/he is dehydrated it may be overestimated. I believe bioelectrical impedance has a percent error of +/-5-10%, compared to skinfold calipers at 3.5%. If using bioelectrical impedance, it is wise to minimize scenarios of over or underhydrating before the test and to take subsequent measurements at the same time of day when hydration is likely to be similar. And for all body fat measurements, they should be done BEFORE you workout.
Ok, now I can answer the rest. With regards to the second question, genetics definitely play a part in where we pocket fat, and certainly play into governing metabolism. In absolute terms (according to texts on exercise), the body fat categories I posted hold true, that a woman with 18% body fat is considered "lean." But another woman, who battles to keep her body fat in a healthy range might consider herself lean at 25%. Both women would fall into "healthy" body fat categories. One would be considered lean by the authorities on fitness, but both might consider themselves lean given their genetics and history. At the same time though, a man with body fat over 20% or a woman with body fat over 30% is in an unhealthy state, regardless of how they perceive their condition.
The third question is really a good one. You are absolutely right that BMI varies among individuals ...that's why the range of what is considered healthy varies from 18.5 - 25. That range doesn't mean that someone with a BMI of 21 is better than someone with a BMI of 24 (similar to your example). It just means that they both fall into a healthy range. As I mention in the post though, the BMI formula can still overestimate people with high musculature. So it does have its problems...
thanks for the responses, l'il schweig. that makes a lot of sense. the only thing i'm wondering about is regarding my second question. i wasn't so much asking about how people perceive themselves; instead, i was asking if it's possible for the same body fat percentage to have different health implications for different people (as in, 27% body fat poses a health risk for female A but does not pose much of one for female B). also, is body fat percentage just defined as weight of body fat as a percentage of total body weight, or is it something more complicated?
Ah, I see what you're asking now. Even if two people have the same body fat reading, someone who carries more of his/her body fat around the abdominal region will be at higher risk for heart disease than a person whose fat is distributed more evenly. You can use waist-to-hip ratio (WHR) to determine if someone is high risk. WHR is calculated by dividing: Waist/Hip. Health risks are high for men when this ratio is over .95 and for women when it is over .86.
And yes, body fat percentage is fat mass/total body mass x 100.
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