The BMI Is BS: How The Weight Loss Industry Uses the Wrong Measuring Stick

Hi guys

this is another great article from Tom Venuto i thought i'd share. I must admit i thought this arguement had been well and truly put to bed by now but iy appears that there are still people in the health industry promoting BMI as a measure of body composition. Not only is it BS as Tom says but it leads people to engage in these crazy type of weight loss programs that promise results like '30 pounds in 30 days as they are misled into thinking weight loss equals fat loss.

The BMI Is BS: How The Weight Loss Industry Uses the Wrong Measuring Stick


Most people who are dieting and exercising judge their success on one number: body weight. If they lose body weight, they feel like they’re on track. If they gain body weight, they feel off track. However, making body weight the only number you measure or even your primary measure of progress is a big mistake.

The weight loss industry is using the wrong measuring stick.

Body mass index BMI

Bodybuilders, who need to be both lean and muscular, are one group of people who have always known about the right measuring stick. But the mainstream diet world is completely out of touch with this critical concept:

The most important success measurement is not body weight, it’s body composition: how much of your weight is muscle and how much is fat.

A perfect example of how the weight loss industry and even respected educational institutions are still failing us is the continued popularity of the body mass index or BMI.

The BMI is a math equation. It is calculated by dividing your weight in kilograms by the square of your height in meters. The resulting number is supposed to tell you if you’re overweight or obese, healthy or unhealthy, based purely on your height and weight.

Here is the BMI rating scale:

Underweight = <18.5
Normal weight = 18.5–24.9
Overweight = 25–29.9
Obesity = BMI of 30 or greater

The Center for Disease Control (CDC) and The Mayo Clinic have BMI calculators on their websites. The National Institutes of Health in Washington DC has a BMI app. This tells me that large, prestigious and influential heath organizations must think BMI is important.

I’m here to tell you that BMI is BS! The BMI tells you nothing about body composition or fitness.

Advocates of BMI say that it correlates with body composition and is a better gauge of health than your weight alone. The truth is, BMI might be an acceptable screening tool for the sedentary broad population. But for many people, BMI is just as misleading as those old insurance company height and weight charts.

For athletes or fitness enthusiasts, BMI is practically worthless for both men and women.

A bodybuilder or strength athlete could easily have a “dangerously high” BMI of 30, but a healthy, low level of body fat. According to the BMI, almost every player in the National Football League is overweight, and some contestants in the Mr. Olympia competition are “morbidly obese” with BMI’s of 40, even though there’s not an ounce of visible fat on their bodies.

If I plug my height (5’ 8”) and weight (195 pounds) into the BMI calculator, it says my BMI is 29.3. That classifies me as “borderline obese.” Anyone who has seen me knows, of course, that this is ridiculous.

As a bodybuilder, I simply have a higher than normal level of lean body mass, so I weigh more than the average guy my height. My body fat level is very low – usually around 10%, give or take a percent or two. That puts me in the “excellent” or “athlete” category for body composition.

Your BMI or your body weight alone can never tell you everything you need to know about your current health or body composition, or the progress you’re making toward your fat loss or muscle-building goals.

Suppose a girl jumps on one of those trendy “lose 30 pounds in 30 days” crash weight loss diets and she actually does drop from 160 to 130 pounds quickly. She weighs less and she’s wearing a smaller size. But was she really successful? We don’t know, because she was only focusing on the scale, which told her how much weight she lost, but not what kind of weight she lost.

If she measured her body composition, she might see that because of the unhealthy fad diet she used, and because she wasn’t doing the right training, she lost only 15 pounds of fat and the other 15 pounds came from lean body mass. When half of your weight loss comes from muscle, that’s not a success.

This also explains how she may fit in smaller clothes, but out of clothes she still looks flabby and un-athletic, like a smaller version of her previous body. She has become what we call, a “skinny fat” person.

If you’re not aware of body composition, the scale can fool you when it moves in the other direction as well. There are two sides to improving body composition: Less fat and more muscle.

Women don’t add muscular body weight or muscle size easily, but men often do. It’s entirely possible, especially for the guys and for beginners to weight training, to gain muscle while losing fat, and the increase in muscle offsets the loss of weight on the scale. If you build muscle, some people may see little or no drop on the scale at all. If you were scale-focused alone, you’d think you failed, but your body composition actually improved.

Body composition is the name of the game and that’s where you should put your focus.

I’m not saying you should ignore your body weight. Some trainers think you should toss your scale in the garbage can, but research says people who weigh themselves have a higher success rate.

What I’m saying is that body weight alone doesn’t tell you the whole story. If you take both measurements, body weight and body fat percentage, you can easily calculate those two critically important numbers: pounds of muscle and pounds of fat.

Here’s an example, using round numbers that make the math simple to do in your head:

Body weight:  200 pounds
Body fat:  10%
Fat mass:  20 pounds (10% of 200 pounds)
Lean mass:  180 pounds (200 pounds total weight minus 20 pounds of fat weight)

Now you’re using the right yardstick – the true measure of success – body composition. And now you know that the goal you’re after is not just a number on the scale.  If you’re moving in the direction of more muscle, less fat, or both, that’s how you know you’re making real progress.

In next Monday’s post, we’ll continue in this thread and answer the question, “Is it really mandatory to measure your body fat?” I think I’ve made a pretty great case for testing and tracking body fat levels, but believe it or not, some trainers are now saying we “shouldn’t bother.”

Until then, Train Hard and Expect Success!

- Tom Venuto

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