My BMI is 23.1.
There are no accurate indicators for body composition assessments. All methods for obtaining body fat have their inaccuracies with the most accurate still being 2-3% incorrect. The only true way to really gauge a person's body composition is to kill them and take apart their adipose tissues and weigh everything individually (this is not sarcasm).
BMI has a major flaw which doesn't include the fact that people have different compositions in terms of fat mass (FM) and fat-free mass (FFM) and only calculates a person's body weigh in comparison to their height. An example could be Shaquille O'Neal from the lakers who weighs a little over 300 pounds but has a body fat percentage of 4%. He is highly trained and fit yet would fall under a category in BMI that would make him grotesquely obese. BMI is a decent indicator for an overall assessment of someone's calculated risk for developing adverse health conditions. We see people that fall into the obese and under weight categories tend to have an increase health concerns such as diabetes, cardiac vascular disease, hypertension, anemia, bullemia, anorexia, and decrease in immune system functions.
The Fat-muscle ratio you mention is going to be correlated to the body composition test of hydrostatic weighing. It's a method where an individual's land weight is taken and then they are placed onto a weight scale submerged in water and another weight is taken. The idea is that the fat density is 0.9kg/l and fat free mass (skeletal muscle, bones and water) have a density of roughly 1.1kg/l. With some mathematical calculations the scaled under weight gives us a projected body composition number for an individual where we can calculate the body fat by taking the weight of the Fat Mass and dividing it by the entire Weight of the Body. This has the smallest room for error but the results can be skewed heavily depending on diet and hydration levels. If someone were to drink 2 liters of water and not urinate before being weighed, they would weigh 2 pounds more and those 2 pounds would be counted as fat free mass which would lower the body fat % result. If you include a heavy meal and drinking some water, one can fluctuate their weight by 4-5 pounds and throw the accurate results off.
My current belief is that studies have shown BMI to be an outdated system. It has it's purpose as I've stated above but it's merely a guideline. The most fascinating thing about the human body to me is that way we see adaptations through different stresses on the body. If you're working out and maintaining a healthy lifestyle you'll see the benefits and reap them. I wouldn't pay close attention to BMI except for the overall big picture related to health concerns. I'd be more concerned about body fat because there are close links to cardiovascular diseases based on higher percentages of fat. Most importantly, just do what it takes to feel great about yourself
My current level of fitness is pretty high. I run 5 times a day for cardio and lift weights 3-4 times a week depending on rotation.
Random facts about me:
I'm 6''0.5' and 170 pounds.
BMI is 23
Body fat from electrical impedance is 6.3%~7.1%. Hydrostatic weighing body fat result is 5.7%.
5K (3.1 mi) running time is 18:58
10K (6.2mi) running time is 51:15
12 mi running time is roughly 2 hours.
Bench press is 3 sets of 245 pounds at 5 reps
Leg press is 3 sets of 630 at 10 reps
Pull ups are at 5 sets of 12 reps with 45 pound plate hanging on me
Dips are at 4 sets of 30 reps with 45 pound plate hanging on me
