If you start a debate about obesity and weight loss, sooner or later you're going to get round to the thorny topic of 'willpower'.
And the conversation might go something like this - 'He's fat because he's lazy and lacks the willpower to stick to his diet'.
Or, 'She should stop moaning about being overweight - if she had any willpower at all she'd go to the gym three times a week.
The queen of catty comments, Katie Hopkins, famously put on, and then lost, three stone in order to somehow prove that people need to 'stop blaming everyone else for problems they can control' back in 2014.
But don't be fooled.
There are some compelling scientific reasons why the notion of 'willpower' is utterly flawed when it comes to shedding excess pounds.
And once you get your head around this fact, it could revolutionise your fitness plan.
Here's why.
By trying to use 'willpower' to stop you overeating, you're embarking on a vain attempt to overrule three millions years of evolution. It's a pointless exercise unless you REALLY know what you're doing.
You see, one of the biggest problems with traditional dieting is hunger.
And hunger is an incredibly powerful urge, coming a very close third to the urge for self preservation and to have sex.
Telling someone who's dieting and is ravenous simply 'use your willpower and don't eat!' is fundamentally useless and doomed to failure - like telling a child to stop her feet growing so you don't have to buy new shoes!
The truth is, only a very tiny percentage of people have the willpower to diet simply by eating less. And an even tinier percentage can keep it up for life.
Sure, we can do it for short periods, but we soon lose motivation.
Willpower is a complete focusing of your desire and intention to achieve a result - and just as you can't drive your car everywhere with the accelerator flat against the floor without quickly damaging it, or others, most of us can't apply our willpower effectively for long stretches without burning out.
When you go back to your 'normal' lifestyle and come off the restrictive diet, the cause of your weight woes are still there.
Worse still, sometimes because of how we've dieted, we've changed our body-composition such that we actually get fatter even if we're actually eating more moderately than we were before we dieted.
So, what's the answer?
I'd argue that the key is to fundamentally re-assess your entire relationship with food.
In in this instance, you might want to think about hypnotherapy sessions - a bit like the ones smokers have if they want to stub-out their addiction to cigarettes - or meditation.
Basically, anything that lets you subtly tweak your natural habits by tapping into your subconscious.
Think of this part of your brain as a dog that you can train - a big, lumbering, friendly but not terribly bright protector which will do anything you tell it to do... but is incapable of making critical judgements of its own.
It's the grey matter that takes care of all the things you don't have to think about - like walking or biting your nails.
Many of us driving a car have 'daydreamed' for several miles only to have absolutely no memory of the journey. You've been on 'autopilot'. That'll be your subconscious taking over.
We've evolved to survive in what was a dangerous environment and much of our low-level behaviour runs automatically to let us concentrate on the important stuff.
This is exactly the reason we develop 'habits' - things we do a few times and get a certain result and then we go on doing them without having to think about them ever again.
Trying to override all that with conscious willpower is, for most of us mere mortals, stressful, frustrating and ultimately disappointing.
Which is why, in short, we all need a little help with it.
Have a chat with a therapist, do a bit of research into something called 'Neuro-Linguistic Programming', a method of developing successful patterns of behaviour, or simply accept you'll eat when you're hungry and make it up for it with an extra long run.
But most of all, stop blaming yourself because, very often, you simply cannot help it!