"Check your payload Captain" | the pilot's guide to trimming down
- Dr. Rob Massera | DAME
- Jun 14
- 4 min read
As pilots, we manage sophisticated aircraft - as well as our own “bio-craft”. In both aviation & health, our weight directly impacts performance and long-term flight safety. Excess weight increases the risk of: high blood pressure, sleep apnoea and heart disease - which are direct threats to your medical certification. In aviation terms, being overweight is an "Undesired Aviator State". So, what corrective actions can we take to return to a healthy weight & balance envelope?
Understanding your bio-craft: Where Does the Extra “Fuel” Go?
Like an aircraft, your “bio-craft” stores fuel (or calories) in two main “tanks” for later use: the smaller (1) Glycogen Tank (short-term fuel) in your liver and muscles is a quick-access fuel for intense bursts of activity & the much larger (2) Fat Tank (long-term fuel): in fat (adipose tissue) - is the long-haul fuel reserve for “cruising”. When your smaller glycogen tank is constantly full, excess fuel is converted into fat - which unlike glycogen - is slow to burn and easy to overfill!
Fuel density & Tank Capacity: Glycogen vs Fat
Just as different aviation fuels have different energy densities, so too do our main fuel reserves of glycogen and fat. Fat has twice the energy density of glycogen (8 calories per gram vs. 4 calories per gram) - this means we must burn TWICE the energy to lose a kilogram of fat compared to glycogen.
Q: What’s the fuel capacity of each tank?
The Glycogen tank: has 400 to 500 grams or 2,000 Calories ~ 1 day of energy endurance
The Fat tank: for the average pilot with 5-10 kilograms of excess fat/fuel or 38,500 to 77,000 Calories ~ 20 to 40 days of energy endurance!
Did you know…Your bio-craft is incredibly fuel efficient? Consider this…
1 litre of AvGas contains 8,000 Calories - equivalent to 1 kilogram of fat - which is enough to power your “bio-craft” for 96 hours (4 days) & your Piper Warrior for just 1.7 minutes!
Q: So how does your bio-craft burn fuel & which tank does it draw from?
Daily Total Energy Expenditure (TEE) or fuel burn is mostly comprised of:
BMR (Basal Metabolic Rate): This is akin to your idling or cruising RPM - just keeping you alive & “airborne” - it accounts for 60% to 75% of your total burn rate.
PAL (Physical Activity Level): is equivalent to your throttle lever - intentionally increasing the rate of fuel burn for “take-of” or “climb” with walking, running or resistance training - it accounts for 20% to 30% of your total burn rate.
Your bio-craft burns a MIX of fuels from each tank - glycogen, fat (& a little protein) - most of the time - however the proportion of each fuel you burn depends on the intensity & duration of exercise:
Low to moderate intensity exercise - (like walking) your body primarily burns fat - glycogen is used but it’s not the main source.
Moderate to high intensity exercise - (like running or resistance training) your body primarily burns glycogen more so than fat - but overtime this increases your BMR.
Endurance training - (like hiking or slow running) for an hour or more initially burns glycogen - but overtime enhances the body’s ability to burn fat.
Bringing it all together | "Fuel planning" to burn off that excess fuel/fat
Like fuel-planning prior to take-off, you can use your excess fuel reserve, daily fuel intake & daily burn rate to "flight-plan" your destination back to a healthy weight envelope.
Excess fuel reserve burn table | Human Bio-craft
As you can see, because fat is so energy dense, an extra 5kg of fuel/fat can take up to 75 days to burn off. This means it takes commitment, persistence and endurance to burn off excess fuel stored as body fat - but it’s well worth it!
So here is a basic "fuel plan" to your “healthy weight” destination
Reduce daily fuel intake: cut your calorific intake by 400 to 500 Calories per day (this is sustainable) + prioritize: lean high-protein meat, high-fibre vegetables, low-GI carbohydrates AND exclude processed or sugary foods - such as: fruit juice, soft-drink, alcohol, cakes, sugary cereals etc. - this will help to reduce hunger.
Increase daily Fluid intake: at least 2.5 litres of water per day helps your liver convert fat to energy and reduce your appetite.
Boost daily fuel burn:
Black coffee - 30 mins prior to light-to-moderate morning exercise helps to switch tanks from the glycogen tank to the fat tank - burning more fat.
Walking - 5 to 7 km every day or 5,000 to 10,000 steps - helps to prioritise fat burning over glycogen - an activity tracking band or watch can really help.
Resistance training: 30 to 45 mins of high-repetition resistance training 2 to 3 x per week - helps to build muscle and increase your BMR - your “idle or cruise” fuel burn rate.
Q: What if my bio-craft isn’t burning off the excess fuel/fat?
Weight gain and weight loss is a multifactorial process & sometimes we need a little extra help to burn off our excess fuel/fat stores - medical options include:
Medications: Semaglutides (Ozempic or Wegovy) can help reduce appetite and support weight loss - particularly in higher BMI or insulin-resistant pilots - However you MUST notify your DAME prior to starting because a 4 week ground-trial & CASA approval is required.
Weight Loss Surgery: for pilots with a BMI >35 + two weight-related comorbidities or a BMI >40 - sleeve gastrectomy or gastric bypass surgery can dramatically reduce excess weight and obesity-linked disease - however you MUST discuss this with your DAME first as it will require grounding until your weight has stabilised & regular blood monitoring.
Q: Who Should You Talk to Next?
You're the “Captain”, but you also depend on a good crew - such as:
Your DAME: To provide AvMed advice and protect your medical certification
Accredited Dietitian & GP: To set up a safe, sustainable plan
Exercise Physiologist or PT: To build your flight plan for fitness
Obesity Medicine Specialist: For advice on medical or surgical options
The bottom line: You wouldn’t fly an aircraft over MTOW - so recognise that being over-weight is an UAS & then take action to correct it - to stay fit-to-fly for the long-haul.
References:
Comments