Body Mass Index and Body Fat Percentage

I felt inspired to write a little more and explain a bit about BMI, BMR, RMR, TDEE and all these other numbers that we like to talk about when we’re doing health and fitness and weight loss. These are all numbers that I use when I build a plan for myself or for a client.

As useful as all of these numbers are, you must remember that their value is as a REFERENCE POINT only, and it is important to apply human intellect in interpreting and assigning a meaning to them. There is a lot of power in numbers but at the same time, we can’t get too hung up on them. 

Body Mass Index


This is the usual intelligence level of your average BMI denier. This guy… I can’t even.

I’ve covered the BMI in a couple of articles already. Its validity is often contested of late, with the dubious logic that since people are heavier now than in the past, we need a new scale that more accurately reflects modern conditions. Which makes perfect sense really… we could solve the obesity crisis quite simply by coming up with a new index where for example I wouldn’t be obese until I hit 100kg, instead of 85kg on the current system. While we’re at it, we can solve poverty simply by printing more money, right?

Clearly that was sarcasm though. Of course people are heavier now. That’s the problem!

Anyway I digress. BMI is just a number, and as stated above its use is as a reference point to compare our current weight to what range of weights we might expect that we should fall into under normal circumstances. It is useful because our self perception is often flawed. Our perception of other people is often flawed too, because we’re so used to seeing overweight people that we begin to think that size is actually normal.

What this is means is that you might think you need to lose weight, and your friends tell you you’re nuts. Are they just being kind, or is your self perception a little off?

So, do you actually need to lose weight? 

Let’s check with the BMI, and I’ll give MY interpretations of the scores.

  • Less than BMI 18:
    You absolutely do NOT need to lose weight. In fact, I FORBID you to lose any more weight. If anything, you should be trying to gain some. If you’re not happy with the way your body looks, we will bump up the calories a bit and do more strength training to improve your body composition. That means you’ll be lean and firm.
  • BMI 18 – 23:
    Your weight is fine. You don’t need to lose any, but if you’re not satisfied with your body type right now, we can work on improving body composition by ensuring we are fuelled appropriately and doing some strategic training.
  • BMI 23 – 25:
    Your weight is fine, but if you do want to trim up a little we can dial in a calorie target expected to maintain a slightly lower weight within the healthy range, and then train to increase lean mass at the expense of fat stores.
  • BMI 25 – 30:
    Technically overweight. How do you feel though? If you’ve been training a while and are carrying some extra muscle and feel good about your body type, who gives a crap what the numbers are? However, if you’re inactive (or just not training effectively) and the extra weight is mostly from excess body fat, we should dial in a good plan to get down somewhere closer to the middle of the normal range.
  • BMI above 30:
    Obesity. In most cases, this means we need to dial in a safe and effective plan to achieve and maintain a weight somewhere in the normal range. There are always exceptions though, and this may be a desirable weight range for some athletes. Myself for example.

This stuff is important especially in regard to people who aren’t overweight and might otherwise attempt an unhealthy diet to an unhealthy low weight, where they still would not be happy with their body even if they were to successfully hit their goal weight. This is a dangerous and common practice that can be prevented by promoting a better understanding of the Body Mass Index. Oh and for the people who actually are overweight or obese, it lets them choose an appropriate and achievable goal.

I must reiterate though, there is no sense at all in being too caught up with what it says on the scales as long as you are somewhere within that normal, healthy range and training strategically towards your goal body type.

Body Fat Percentage

Here’s another one I don’t want people to bother too much with. I’ve had the conversation a couple of times now with people who are so happy with their progress that they decide to “treat themselves” to a proper scan to accurately measure their body fat percentage.

Bad move, in my opinion. What number would you need to see on that test score in order to still be happy?

Here are the possible outcomes as I see them:

  1. You go in with no “ideal” number in mind. No matter what number the test comes out with, you’re not happy any more.
  2. You go in with an “ideal” number in mind that will confirm that you’re in great shape and justifies being so happy and proud of yourself. The test gives a higher number, and you’re not happy any more.
  3. You go in with an “ideal” number in mind that will confirm that you’re in great shape and justifies being so happy and proud of yourself. The test confirms what you knew already.

Bottom line: it’s about how you feel about yourself, not about numbers.
We use the numbers as a tool that empowers us to make the right decisions and choose the correct course of action that will lead us to health and happiness. We do NOT let them tell us how we should feel about ourselves.

More tomorrow!

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Author: davehpt

I'm DaveHPT, Maybe you've heard of me? Musician, rock star and recording artist. Published author. Former security industry professional. Personal Trainer and Weight Management Architect Of Awesomeness. Problem Solver.

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