Do what I say, not what I do

By what markers do you judge your trainer? Why do you trust them to tell you what to do in the gym, at home, in the kitchen, even on holiday? My best guess is that initially, it's going to be because they represent something that you either respect or would like to emulate. They're either fitter than you, leaner, stronger, more physically able or some other physical facet that encourages you to think, 'this person knows what they're talking about'. They're walking the talk. Or they're just good looking. Does this necessarily mean they're a good trainer?

In some ways, no. Their education may be sorely lacking. They may just be gifted with a high pain tolerance and good genes. They may simply be one dimensional morons with a basic knowledge of bodybuilding and an 'education' gleaned from the pages of tripe filling muscle and fitness magazines, their skills tempered and honed by 2 six week courses that rehash year 10 health science.
After all, do we rely on our true medical professionals, doctors and surgeons, to be paragons of perfect physical health? Far from it. These highly trained, highly educated individuals are in the same boat as your average corporate executive. Highly stressed, possibly enamoured of cigarettes, alcohol and the richer food that a financially rewarding position can bring, they often find themselves subject to the pharmaceutical and surgical skills they bring to bear on others.

Why then, are we not concerned if our heart surgeon is lean and muscular, but we scoff at trainers who look little better than average? Look at it this way: If your heart surgeon said, "I've read all about this heart surgery stuff, I've watched dozens of videos, it looks pretty straightforward", you'd probably be seeking a second opinion, possibly in another hospital. By the same token, if your trainer is overweight or unfit, or doesn't display any of the characteristics you'd like to achieve, then how would they know what it's like to strive for them? You can understand the physical principles of riding a motorbike, but until you've ridden one, you wouldn't instruct someone else on the necessary skills.

So in some ways, your trainer's appearance is definitely a marker of their quality. If they're not willing to put in the effort that they expect you to put in, how do they know if their prescription is actually effective? After all, the fitness industry is supported almost entirely by myth, hype and even outright lies, so if they can't demonstrate that it works, why bother listening to them?