When health numbers don't add up: weight, BMI and body composition

Photo by Tyler Raye on Unsplash

This is what I did not expect to see when I started working with patients who are on GLP-1s: increasing and borderline anxious focus on the number on the scale --- as if an obsession with food transformed itself into an obsession with a number.

- "I was 181 yesterday, and today I am 183 lbs... I gained weight again!!!"
- "No, you didn't."

WEIGHT:
So, first, let's talk about number on the scale, shall we?
Fragment of post in my office hanging right above a scale states: "The scale can only give you a numerical reflection of your relationship with gravity". And - I may add - only at this very moment.
Your weight fluctuates, and in some cases a lot, and it is a good thing: that means you are alive!
You may wake up a bit dehydrated, and so your weight will register as "lower".
You may wake up with puffy ankles and bags under your eyes, and so the scale will show a higher number.
Logical.
You eat lunch - you are heavier.
You poop - you are lighter. 
Weight can fluctuate several pounds up and down thru the day, so if you step on a scale today at 6.00 pm, this is your weight at this very moment.

If my patient is 181 lbs, 183 lbs, 180 lbs, 179 lbs, 182 lbs, 183 lbs --- I would consider it a stable weight, not a "weight loss" between May and June or "weight gain" between June and July. But the story is more nuanced.

- "I am doing everything that I should, and my weight does not change..."
- "Do you clothes fit differently?" - I ask.
- "Oh yes, I can fit into the dress that I was not able to fit into last year!"

Then you are losing weight.
Or more precisely you are losing excessive fat tissue.
And if you are "doing everything that you should", including eating an adequate amount of protein, hydrating well and exercising on the regular basis, you may be building muscle at the same time.
You are effectively swapping one weight source (fat tissue) for another (muscle mass) and so the number on the scale doesn't budge, but your body composition changes dramatically. And this is a true secret of health. 
Higher muscle mass equals higher metabolism too, which means you can eat a bit more and still maintain healthy weight without difficulties.

So instead of looking at the number on the scale ask yourself:
- Am I seeing inches in my waist melting away?
- Am I on the market for smaller pants (even if my weight is "the same")?
- Am I seeing a hint of a muscle definition anywhere on my body? Or, if not (yet)
- Do I feel stronger?
- Are activities that were difficult (like carrying heavy grocery bags up the stairs) easier than they were?
- Do I have more energy?
- Do I find myself walking faster or being able to do certain exercises for longer, without feeling as tired as I felt in the past?
- Do I sleep better (that's often a result of increased activity thru the day)?
- Are my laboratory values (blood pressure, cholesterol, blood glucose) improving?
If you see changes in these areas, you are moving the needle in the right direction.
Even if the "weight" does not change.

BMI:
It is hard to talk about weight and body composition and not touch on BMI. 
BMI, originally, was never meant to be a health marker for individuals; it was designed to be a statistical population-wide tool, and (cringe warning!!!) it was designed using weights of only typical white males - no corrections for breasts, butts or hips, or just our unique and diverse body shapes. 

Further, BMI is nothing more than a calculation that takes your height and weight and spits the number on the other side of the equation symbol. That's it. It just calculates relation between two numbers without any insight into body composition.

A fit, muscular person with low body fat percentage may show up as overweight on the BMI scale, simply because of the amount of muscle.
Case scenario:  Arnold Schwarzenegger: his weight during his prime body/muscle building time was 235 lbs (107 kg). His height at the time was 6'2" (188 cm) (Thank you, Google! :) ). You plop these 2 numbers into a BMI calculator, and the number you get on the other side is 30.2 which puts him in... obese category.
What am I supposed to tell him, as a dietitian?!? - To exercise more?

A person with advanced osteoporosis (thinner, low density porous bones) and excessive fat tissue ("making up" the weight difference) may show up as "healthy weight" on BMI scale, when in fact they have serious health conditions.

So:
Eat well. Move. Sleep well. Take care of yourself.
Nourish your body. Get stronger. Get healthier. 
Understand what weight and BMI tell you, and more importantly understand them in context of your health.  

You can be skinny and sick.
You can healthy, muscular, strong and appear a bit overweight on that - whether we like it or not - very imperfect measurement tool.