Is BMI Still a Useful Tool for Weight Loss?

Weight Loss

BMI has been used for years as a way to measure how healthy somebody is, but the validity of these results has started to be called into question.

bmi calculator

BMI stands for Body Mass Index and refers to a numerical value created from your weight compared with your height. This value is then separated into certain categories labelled after what it means for your health.

  • Under 18.5 – This value means that you’re underweight and possibly, malnourished.
  • 5 to 24.9 – This is the healthy range for adults to be in, meaning that your weight is at a good level for your height.
  • 25 to 29.9 – If you’re in this category, then you’re considered overweight, but not obese.
  • Over 30 – This refers to those who are clinically obese and therefore, their weight is a severe threat to their health.


These ranges differ depending on if you’re an elderly member of the population or a child, but for general people, these are the ranges to go by.

On the surface, this seems like a useful and worthwhile tool that can indicate facts about your health albeit not specific. Yet, the specificity is where the issues arise as it’s only comparing your weight to your height, and weight can mean anything. For instance, your weight can mean fat, but it also includes muscles, bones, organs, and water. If you’re particularly dehydrated on one day or don’t have as much food in your stomach, then your weight can be considerably lower.

Let’s look at an example of two 30-year-old males who both weigh 180lbs at 6ft. One man regularly goes to the gym, eats a balanced diet, and makes sure to remain active. The other man lives off junk food, rarely gets any activity, and is generally sedentary. Although both of these people might look the same in terms of height and weight, their body composition is entirely different. Therefore, their BMI will both be the same at 24.4 (at the upper end of healthy), but one man is clearly much healthier than the other.

The same can be said for two individuals who are underweight or overweight. Those who carry a large amount of muscle are frequently placed in the overweight category simply because their muscles weigh so much, but they are by no means unhealthy.

Though, does this mean that BMI is a completely useless tool? No, not quite. All it means is that you need other data alongside it. This other data can come from body fat measurements or pictures which you can them compare with the results from your BMI. For instance, if your BMI says that you’re overweight but your progress pictures clearly show that you’ve gained a large amount of muscle or your body fat percentage is in a good range, then you know that you’re healthy in terms of body composition. However, if your BMI says you’re overweight and either your pictures or body fat measurements also show you’re carrying a little extra weight, then you know that it’s time to start dropping fat. Equally, if you’re BMI says you’re in a healthy range, but your fat percentage is a little high, then you know your weight might be in a good range, but you still need to lose some fat.

BMi is also a good way to find out what weight category you’re in as by just looking at yourself in the mirror you may not know whether you’re slightly overweight or clinically obese and need to make a drastic change. Because of this, BMI can be useful in directing you towards the degree at which you need to make a change.

At the end of the day, BMI isn’t completely useless, but just like any tool, you need to know how to use it correctly. It’s a bit like using the handle of a hammer to hit a nail and thinking then throwing it away for not working. You’ll notice that many doctors and health professionals still use BMI or bmr calculator, and for good reason, too. Don’t place too much value in one tool as this will only give you a single perspective. Instead you need to use a variety of tools in order to see the whole picture and work out what you need to do from there.