We bill insurance based on BMI. Unfortunately, the body mass index does not consider everything. The study done to create the BMI chart was attempting to prove correlation between weight and chronic disease risk. It was correlated, and the health industry took it as gold. Unfortunately, our recent research has not overcome this outdated pillar. In 2013 when obesity was diagnosed as a disease, it was finally time to address the elephant in the room. Yes, obesity increases risk of chronic disease. But obesity it not weight, it is excess fat tissue. So why do we continue to recommend weight ranges without reference to muscle mass? In our modern society we have a much larger focus on muscle growth. We eat more protein, exercise in more muscle promoting ways, play more intense recreational sports. Additionally, those suffering from obesity are carrying around hundreds of pounds. If you wore a 100lb weight vest all day, every stair case is a lunge, every time you sit up and down a squat, and walking is a form of moderate intensity cardio. If you did this for hours per day, you would build muscle. So do those suffer from obesity! So now it is time for them to lose weight. Why are we telling them to conform to a weight range from 60 years ago with limited muscle mass? It makes more sense to remove the tissue (fat) that we know causes the chronic disease. Preserving muscle becomes beneficial and practical. Enter body composition assessment.
We now know the body fat ranges that more precisely define obesity:
Body Fat Ranges:
8-12% extra lean
12-15% lean (Ideal)
15-18% normal (ideal for less active)
<20% goal for males over age 40
16-20% extra lean
20-24% lean (ideal)
25-30% is normal (Ideal for less active)
35% and below ideal for 50+ (shoot for 30% or lower)
These values allow us to see how much fat a person needs to lose to reduce the hormone cascade fats cells cause. This reduction in signaling means reductions in blood pressure, blood sugar, cholesterol, and as a result chronic disease progression. They also tend to excite patients, and help them feel like their goal is more personalized, logical and attainable.
Ex: 6’, 300lb man with 30% body fat
300lbs x 30% = 90lbs of fat mass, 210lbs fat free mass
So this man has 210lbs of muscle, bone, skin, organs, water etc. Why would we tell him to weigh 176lbs for the BMI chart?
I always assume large guys lose 10-15lbs of water weight. So if he has 195lbs fat free mass we want to keep (210ls-15lbs water), and we want him at 15% body fat, that is 195lbs/85% = 230lbs. That is this man’s IBW after accounting for his muscle mass. At that weight he has no excess fat, which means no adipocyte stimulated hormone flux, and no risk of chronic disease related to body composition. Are his muscles causing diabetes? No they stimulate GLUT 4 and use sugar. Are they affecting his cholesterol and blood pressure? Not likely, their function leads to HDL increase, use of fatty acids, and vasodilation…
Now we have a 6’ tall man with an encouraging and practical goal based on modern science.