Your BMI is Not BS

It wasn’t the medical profession who first made the connection between obesity and ill health; it was the insurance industry. In the early 20th century, life insurance companies noticed an increased number of deaths in heavier people. This discovery resulted in policies based on the, rather antiquated, idea of a “desirable” weight.

It wasn’t until a short time after the Second World War that, solid, clinical discoveries were made about obesity and the increased risk of diabetes and cardiovascular disease. Like in insurance, years earlier, clinicians wanted the ability to group people to predict health risk. To do this they adopted a system invented by a Belgium astronomer in the 1830s. In 1972, they renamed his system the body mass index, and BMI was born.

Since then, the body mass index has gone in and out of favour as a clinical tool and is now perhaps more unpopular than ever. The question is, can a guide invented so long ago still be valid today? The answer is yes. Here’s why your BMI is not bullshit.

BMI is controversial in the health and wellness trade. In the more liberal corner of the fitness industry, having a number that boxes people into healthy-weight, overweight, or obese is a pointless label that has nothing to do with body composition or health status. Others rely on BMI as both a starting and ending point for goal-based programs. Both of these positions miss the point. BMI is neither nonsense nor absolute, it’s a screen.

The heavier you are for your height, the more your risk of all manner of nasty diseases goes up, but you can have a body mass index that says you’re obese but still not have any metabolic consequences. BMI doesn’t tell you if you are sick or not; it’s a tool to predict the likelihood of getting sick. On a population level, BMI teases this out quite well.

Some of the current issues with BMI come from people who are classed as overweight, or obese but exercise regularly or lift heavy weights. Their feeling is that even if they’re obese by the BMI standards, the amount of muscle they have is skewing the results. However, we need to be cautious with this approach. Many of us aren’t quite as fit as we think.

If you think the numbers don’t matter because you have more muscle than the average, it can help to compare yourself to others in a bid to be more objective.

Here’s a photo of personal training expert Gordon Greenhorn weighing 80kg. At the time of this photo, he could squat 215kg, bench press 155kg, and deadlift 247.5kg. Despite, clearly, having a solid amount of muscle, his BMI was 25, making him just 0.1 points over healthy and into “overweight” by body mass index standards.

If you want to see how colossal you need to be to get an obese BMI from pure muscle, check out Arnold in his prime below with a BMI of exactly 30.

While we might overestimate how well trained or muscular we really are, there are still plenty of us who can be “overweight” as per a BMI measurement and still be perfectly healthy. BMI can give us a heads up, but it makes some pretty lofty assumptions about your body composition. We have a better idea of our status when we involve other tools. Excess weight, and especially excess fat can lead to health problems, but it’s not just about how much fat you have; it’s where you carry it.

The fat around your middle is a greater risk than fat found on other parts of your body. This visceral fat, that coats your internal organs, is the stuff that is most dangerous but, luckily, your waist circumference can be measured quite easily with nothing but a tape.

Just as BMI predicts health risk, there is similar data in waist circumference.

As waist circumference goes up, so does the same risks of the same diseases that are predicted with a high BMI. So even with a normal BMI, if you have a large waist circumference you can be at a greater risk of obesity-related diseases. This is good news for us because it gives us an extra tool and a way to make a simple measurement like BMI much more nuanced.

According to the NHS, men with a waist size of 94cm or more and women with a waist size of 80cm or more are more likely to develop obesity-related health problems. Unlike with BMI, where you can be heavier and still healthy, if you have a larger wast size than these two examples, it’s much more likely that you have an excess of, unhealthy, visceral fat.

Now that we have all of the information we need, let’s take a little bit of time to get practical.

If you have a BMI of 30+

If you are not an athlete bodybuilder, I would really recommend weight loss to avoid any health complications down the line.

If you are a high-performance athlete who benefits from a higher weight such as a rugby player, American footballer, or heavy powerlifter, or Arnold Schwarzenegger, you might still be at risk of some of the negative health issues associated with obesity. Take these two steps:

  1. Check your waist circumference
  2. If it’s greater than 94cm for men, and 80cm for women than weight loss should be a practical consideration

If you have a BMI of 25+

If you have never lifted a weight in your life, your BMI is likely worth paying attention to. Weight-loss and/or structured exercise are good considerations.

If you hit the gym and are legitimately more jacked than most people, you might not be at an increased risk of any, potential, negatives. To be sure, take these two steps:

  1. Check your waist circumference
  2. If it’s greater than 94cm for men, and 80cm for women than weight loss should be a practical consideration

Health is much more than your height and weight, but your body mass index is a good starting point, and if you lift weights a few times a week it doesn’t make the number meaningless. Your BMI is not BS.

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