BMI Tests For Pilots: Avoiding The Issue

The proposed addition of neck circumference and BMI testing to the airman’s medical exam is inaccurate, misguided and of limited usefulness. The impetus behind this screening is the recent spate of tired pilots making mistakes and even falling asleep while on duty. In one such incident it was later revealed that the captain had sleep apnea which was viewed as a probable cause for his falling asleep enroute (since sleep apnea is not contagious, the reason for the first officer also falling asleep at the same time was chalked up to fatigue). While this change to the medical exam affects all pilots, including those who fly privately, this piece will focus on air carrier pilots.

Aviation is under a constant media microscope and these incidents while statistically miniscule, nevertheless raise the suspicion of the public. Falling asleep at a job as hazardous as those that exist in aviation should not be tolerated, but using a questionable screening process should not be accepted in an attempt to create a solution to a condition that may or may not exist and most likely is not the primary cause of exhausted pilots. For the record, each year there are over 100,000 motor vehicle accidents that are attributed to drowsy driving. Despite the loss of 1,500 lives, so far no public safety department has mandated obesity or sleep apnea tests for motor vehicle drivers, even commercial operators.

Body Mass Index Accuracy

It has been proven that people with extremely high body fat percentages are susceptible to obstructive sleep apnea. It has also been proven that sleep apnea causes both hypersomnia and insomnia, impairs cognitive function and can lead to cardiac arrest in extreme cases. These facts are also not in question. What is troubling is the method being used to determine this risk factor in pilots, namely, the BMI rating.

BMI, or body mass index is a handy method for calculating a person’s mass to height ratio. As such, it is useful as a quick evaluation concerning obesity. The problem with BMI is that it is a very “dumb” equation; it does not know what it is measuring. A “smart” doctor, trainer, or clinician has to interpret the number and take into account other physiological factors (even the CDC states that BMI is not a diagnostic tool). Unfortunately, because BMI requires no specialized equipment or tactile measurements on the patient, it is widely used by people who have limited knowledge about the human body, obesity, bone density or muscle mass. This results in gross misinterpretations and misdiagnosis for people of various body types.

Another problem with BMI is that it leaves out critical factors such as age, gender, and body fat percentage. As people age, they naturally lose muscle mass unless steps are taken to preserve it (such as lifting weights). The loss of muscle mass, while detrimental, will show up as a reduction in BMI, leading the patient to think that they are getting healthier. Women on average have less muscle mass than men, resulting in more women being classified as healthy and more men as obese, even if the opposite is true. And most tellingly, if a person is 5’8” and 190lbs with 8% body fat, they will score the same BMI as someone who is 5’8”, 190lbs and 30% body fat (it is the same logic as saying that a Ford F-150 and a Ford Mustang will perform exactly the same since they have the same horsepower). One would think that scenarios such as these would be easily noticed and accounted for, however that does not appear to be the case in several well publicized instances.

In recent months, stories have come out where middle schools with good intentions unwittingly labeled some student athletes as “at risk” or obese based on a BMI calculation. The fact that nobody in charge of the program even understood how to deal with off-scale errors caused by a student having more muscle mass than their peers is distressing. Part of this rampant misinterpretation stems from our nation’s obsession with weight as the be-all-end-all indicator of a person’s health. Weight alone is a useless metric. It merely tells us how much of an effect gravity has on a given person. It does not tell us the distribution of body fat or muscle mass, which are the critical values that directly affect a person’s well-being. And as previously mentioned, simply possessing the stats of being 5’8” and 190 lbs only means that you are 5’8” tall and 190 lbs. Any other inferences must be determined by checking body composition.

As angry as the students and parents were at this mislabeling, imagine if your job relied on BMI numbers that may not have any basis in reality. It has been shown that it is very easy to make sweeping generalizations based on spurious data and then pass off any errors as anomalies. Will an airline ignore high BMI numbers in a visibly fit pilot, or will they tell them to atrophy away some muscle mass in order to lose weight? Alarms should be going off in the head of every pilot in America. If it can happen to children in school, it can and is about to happen to them as well.

Flight Fatigue

The cockpit of a modern jetliner can be a very sleepy place physiologically speaking. Noise fatigue from the slipstream roaring past the windows (a very effective white noise generator), reduced oxygen levels even with a pressurized cabin, and the inability to simply stand up and walk around are just some of the fatigue inducing factors present. Any one of these factors by themselves are hazardous enough to have volumes written about their attendant risks. Somehow, they are not even mentioned as a possible factor in pilot fatigue in this new screening process.

In fact it is entirely possible that it is an attempt to divert attention away from the fact that the new rest rules enacted by the Federal Aviation Administration have not fully accomplished their goal of eliminating pilot fatigue. This is only because airlines are not required to fully implement these rules until the end of 2013. Federal regulations now allow air carrier pilots a maximum of 9 hours of flight time and at least 10 hours of rest per each 24 hour period. To those who don’t fly for a living, a 9 hour workday does not sound that difficult and 10 hours of rest seems like it should be adequate. In reality flight time only accounts for loggable time in the aircraft (in airliners, the parking brake serves as the aviation equivalent of a time clock).

The new rules do a much better job of eliminating fatigue due to deadhead commuting and excessive duty times. Preflighting, checking weather, waiting for ground stops to expire, briefing, and all other tasks directly associated with preparing to fly an aircraft are limited to no more than 14 hours per day. Unfortunately, traveling to the airport, leaving the airport and checking into hotels all accounts for time that is not yet definable by the FAA.

Confusion abounds in the general public as to how a pilot halfway through a 3 hour flight can fall asleep. While that one flight is only three hours, it may be the second flight that day on the third day of a four day trip away from home. Anyone who works 9 to 14 hours is going to be tired. Anyone who works 9 to 14 hours going back and forth between time zones, sleeping in unfamiliar beds, unable to establish a consistent exercise regimen and not having access to healthy, agreeable foods is going to be even more tired. Now ask that person to stay alert in an environment that is almost custom built to induce sleep for four days in a row. This is the real reason why pilots are tired, make mistakes and fall asleep. When two pilots fall asleep and overfly their destination, or when critical mistakes are made due to fatigue induced cognitive impairment, the last thing that should be looked at is sleep apnea. Is sleep apnea a risk? Absolutely, but in the long list of causal factors it is not anywhere near the top.

The combination of desire to generate profit, maintain public confidence in aviation and ensure pilots are not forced into unhealthy patterns is a difficult river to navigate. The FAA has tried to close a massive loophole in their prior regulations via their current definition of Flight Duty Period. Airlines have historically exploited this oversight and were against changes to the Flight Duty Period limits (see page 112). Currently the issue is that duty time ends once the aircraft is parked, not when the pilot arrives at the hotel (we are assuming the pilot is in the middle of a multiple-day trip and cannot simply go home). It can easily take an hour to go from the cockpit to a hotel room, sometimes more. Assuming the pilot eats immediately, that leaves roughly 30 minutes before they are supposed to be sound asleep in order to take advantage of the “8 hour uninterrupted sleep opportunity”. In the morning, the reverse is in effect as it takes a similar amount of time to get to the airport and check in at the crew room. It is easy to see how the 8 hours of sleep can quickly erode to 6 or less. As a good friend who flies for a major air carrier said, “The new rest rules need to address the fact that we can’t go to sleep while making the first turnoff, nor can we wake up at V1.”

Instead of neck circumference and BMI tests,  there should be demands for better scheduling practices for all air carriers. Require that pilots get up and walk around the cabin for a couple minutes every hour (security rules be damned). Mandate that pilots take a few breaths from their O2 masks whenever they feel tired. Implore the FAA to close the final loophole in the definition of Flight Duty Period. Consolidate preflight tasks or delegate them to a dedicated ground crew much like military does with its crew chiefs. Install better soundproofing insulation in cockpits to reduce noise fatigue and hearing loss. Encourage airlines to create dedicated “pilot apartments” at their bases to eliminate travel time for the crews. Any one of these potential solutions solves multiple major issues facing pilot workplace health, which is the most effective way of mitigating the fatigue issue.


Should obesity screening be conducted? Considering that airline pilots must possess a 1st class medical certificate which can only be obtained after a battery of tests including an EKG, it seems odd that severely obese pilots are just walking around by the thousands. Many aircraft are tough to fit into even for an average sized person, so there’s yet another barrier to the truly obese sitting in the cockpit. But for the sake of argument, let’s say that there is a sizable population of obese pilots. There are far more accurate methods of determining levels of adipose tissue distribution than a distorted height to weight ratio. Aerospace Medical Examiners are certainly intelligent enough to use methods such as caliper skinfold or bioelectric impedance to make the necessary measurements. Then that physician can make recommendations on what the pilot can do to reduce their body fat percentage. Focusing on body fat, not weight, will have a far more effective result on the pilot’s overall health than zeroing in on one potential condition.

Flying aircraft is mentally and physically taxing. Pilots are still just mere mortals who have the same body the rest of us have. It requires food, exercise and sleep or it will not function optimally. To expect them to operate like machines is not realistic. Airlines need to accept this, the FAA has to continue to support this and pilots themselves have to live with this. Until it is determined that fixing the underlying causes is worth the cost, we will continue to see more pilots making fatigue induced errors and overflying destinations while fast asleep.

Suggested Further Reading

Center For Disease Control: “About BMI For Adults
Sept 13, 2011
FAA: “New Obstructive Sleep Apnea Policy” ; Fred Tilton MD
November, 2013
Mayo Clinic: “Sleep Apnea
July 24, 2011
FAA: “Fact Sheet – Pilot Flight Time, Rest and Fatigue
January 27, 2010
FAA: “Flightcrew Member Duty and Rest Requirements
December 21, 2011
The Sleep Foundation: “Sleep Studies
National Institutes Of Health: “Neck Circumference And Other Clinical Features In The Diagnosis Of Obstructive Sleep Apnea Syndrome” ; Robert J.O. Davies, Nabeel J. Ali and John R. Stradling
October 24, 1991
NHTSA: “Drowsy Driving And Automobile Crashes” ; Kingman P. Strohl MD, et al
International Journal Of Obesity: “Accuracy Of Body Mass Index In Diagnosing Obesity In The Adult General Population”; A. Romero-Corral, et al
February 19, 2008 “Summary Of Pilot Medical Standards
February 26, 2007

Breaking The Chain

I have many alter-egos, one of which enjoys flying airplanes. One thing to know about pilots is that we are almost obsessed with accident reports. Not from a morbid point of view, but from a “you’ll never live long enough to make all the mistakes yourself so learn from someone else’s misfortune” standpoint. About 99% of the time, accidents are the last link in a chain of events that began usually before the plane ever left the ground. In some cases, things that happened days or weeks before the final flight play a role. Investigations therefore can take months and by that time, the 24 hour news cycle has moved on, leaving the public to assume that the immediate “OMG THE PILOT DIDN’T FILE A FLIGHT PLAN” speculation of what happened was the actual cause.

In the exercise world, things are much safer, but the long link of an “accident” chain can still affect you. Injuries are often the culmination of bad form over time, or a distraction combined with lack of sleep, or maybe rushing to finish by a certain time. Using aviation styled investigation methods, you can probably go back at least 12-24 hours to find a whole host of factors that conspired to result in you sitting on the floor in pain wondering what happened. Here is an example of how innocuous these factors can be.

Last week one of my clients wasn’t feeling well and cancelled our appointments. Today was the first time I had seen her in close to two weeks due to her work schedule. In that time the daily temperature had gone from mid 60s to high 80s and very dry. She showed up ready to work as she had 5 sets of squats to get through before doing some lighter lifts. After a couple warmup and reorientation sets (drive through the heels, feet a little wider, now it’s coming back, you’ve got it now), she went to her first working set. The weight for the working set was the same as it was the last time she worked out, however the number of reps was lower to compensate for her absence. After her second set, she leaned into me and said she didn’t feel right and was slightly dizzy. That and her arms felt very weird, like they didn’t belong to her. Knowing that out of body experiences during exercise is generally not a good thing, I immediately took her into the hallway where there was a breeze from the air conditioning unit and had her sit on a bench. Needless to say the rest of her training was cancelled and I made sure she sat for a long time and drank plenty of water before sending her home (with a mandated stop to get food on the way). What went wrong? A conversation with her revealed a lot of things that played a role:

1. A week before she had a stomach virus. That depleted energy reserves and also reduced the number of calories she ate for that week. So her body was still playing catch-up by the time she got to the gym this week (2 causes).

2. She did not sleep very much the night before our workout (1 cause).

3. Our training time was at 5pm. The last time she ate was breakfast at 6am (1 cause).

4. The gym was extra warm due to the 5pm rush of people. We forget how much heat a human body can generate, especially when it is expending energy (humans at rest generate roughly 70-100 watts, those working out can output anywhere from 500-3000 watts depending on intensity). Collect 50 people in a small space, add in big windows and Texas afternoon sunshine and the air conditioning system that worked fine at 1pm can quickly be overwhelmed (3 causes).

5. Her workout attire was heavy, which I should have noticed and made adjustments for. The last time we worked out, the outside temperature was at least 15 degrees cooler. She admits to buying her moisture-wicking pants during the winter so she could go on long runs without getting cold. This morning she just threw them in her bag without thinking about the weather. The same held true for her shirt, which was a thick 100% cotton t-shirt (technically 2 causes).

6. Her breathing was very shallow on her sets. This is something else I have to be more proactive in correcting with everyone since just saying “deep breath” doesn’t cut it (1 cause).

There you go. At least 10 separate causal factors led to her not feeling well. Just like an aircraft accident, the initial response of untrained observers would simplistic and incorrectly obvious like, “You pushed her too hard!” or “See? Squats are evil!”. The fact that her workload was lower and she felt the effects early in the workout show that it wasn’t the exercise alone that caused it. It took some Ed Bradley style investigation to backtrack and discover the true genesis. There is a good chance the situation could have been avoided if I had demanded more details when I asked how she felt before we started working out. I always ask my clients if they feel good, but the way I say it probably sounds more like a trainer greeting than an actual inquiry.

In aviation, we use checklists to make sure that important items pertaining to aircraft operation are not forgotten. The widespread use of checklists has prevented thousands of accidents over the years by reminding pilots of what needs to be done when memory alone would be unreliable. We also use checklists to verify that our own bodies and minds are ready to assume the responsibility of piloting an aircraft. Having a solid way to measure risk can be helpful when determination, ego, inexperience or scheduling issues are trying to force you to do something that your body is quietly protesting. The most popular one, IMSAFE can easily be applied to workouts.

Try using this checklist for yourself the next time you train. You may be surprised but I guarantee there will be at least one item on the list that you are deficient in. That’s not a problem, as long as you know ahead of time and make appropriate adjustments in your program. If you have a lot of items marked, that’s a sign that you may want to defer the workout to a later time (sometimes having a light meal and waiting a couple hours can make all the difference in the world).

As we head into summer it is critical to pay attention to our environment and our bodies to ensure that we are indeed ready to exert ourselves. Being diligent can stop the accident chain from progressing to an undesirable conclusion. I encourage my clients to cancel if they don’t feel right and you should too. Despite what many trainers will tell you, you don’t HAVE to workout…at least today…if you don’t feel right. Wars will not erupt, tsunamis will not inundate the eastern seaboard and comets will not bombard the earth if you skip your lifts. When you only got 3 hours of sleep before working a 10 hour day with no lunch, its better to go home, eat, sleep and do the lifts on a day when you’re fully alert and fuelled. Going in exhausted means that at best, you’re half-assing it and at worst it means the ambulance shows up.

Oh and if your trainer makes you keep working out after you get dizzy, nauseous or otherwise disoriented, fire them.