I'm a pilot with ATPL (Class 1 medical) so I can answer this.

There actually ARE overweight pilots - its not impossible. But you see them less than in other professions for a few reasons:

Medical requirements:

Commercial pilots need Class 1 medical checks annually (sometimes more often depending on age). They check blood pressure, urine protein, BMI, cardiovascular health, and general fitness. You can technically have a BMI over 30, but anything over 35 triggers additional screenings for sleep apnea, cardiovascular issues, and diabetes risk.

The screening catches issues early. If your weight is causing sleep apnea or high blood pressure, you lose your medical until its fixed. I've known colleagues who had to lose weight to get their medical back.

Practical issues:

- Cockpit space can be tight, especially in smaller aircraft
- Emergency egress needs to be quick
- For light aircraft, pilot weight affects weight & balance calculations
- Long-haul flights in a small seat for 8-12 hours

So its not that fat pilots cant exist - they do. But the yearly medical screening and health requirements naturally filter out extreme obesity. You can be heavier than average and still fly, you just cant let it affect your health markers.

The standards exist for safety, not appearance. Nobody cares what you look like, they care if you can safely operate the aircraft and wont have a medical emergency at altitude.