The most sensible thing any weight-loss guru ever said to me was this: "There's no point me telling you anything about dieting. You already know what constitutes healthy eating. We all do. The issue isn't wisdom, it's willpower."
And yet every time another news story appears, vilifying one ingredient or lionising another, we clamour for a quick fix. This week, we learn that it's not the presence of junk food but the absence of good food that is expanding our waistlines while curtailing our lifespans.
Actually, there's nothing new in that - I recall a dietitian telling me that selfsame thing in 2002, but deja vu is par for the course when it comes to the latest, greatest theories of how to eat ourselves fitter, not fatter.
I vaguely remember him saying that adding blueberries and spinach to an overweight person's diet would be far more beneficial that simply cutting calories. But don't quote me or indeed curse me when there's a run on the frozen food cabinets at Sainsbury's.
Not least because such hyperbolic health kicks don't generally last, and they'll be back in stock before you can peer past the bags of mixed veg and say, "Ooh, I didn't know they still made Viennetta!" quickly followed by, "But they've shrunk - better buy two."
For most of us, eating healthily at every meal, every day, is hard.
It's easier to respond reactively than to instigate change proactively - unless you see a pic of yourself on holiday in a vest and are so upset that your arms are three times the size of your head, you crash-diet your way into the tabloids.
But for the majority of the population, the sheer weight of evidence about the sheer weight of us is nothing short of overwhelming. Findings published in The Lancet reveal that bad diet now accounts for one in six deaths every year.
Almost 90,000 British people's lives are being cut short because of what they eat - or, more saliently, don't eat.
Low intake of fruit, veg, wholegrains and fibre is a marker for diet-related diseases such as type 2 diabetes. So, too, is excessive consumption of processed foods, fat, salt and sugar.
The shocking death toll is about the same as the figure for those killed by smoking. As a society, we feel able - indeed, obliged - to intervene when someone we care about continues to light up despite health warnings.
The world offers unconditional support when someone tries to kick the habit and wouldn't dream of trying to tempt them with a cigarette. Similarly, those who have stopped drinking alcohol due to addiction are largely treated with respect.
But making poor food choices remains a taboo subject, even though the consequences are every bit as appalling.
"I have lost track of the times when colleagues and family have actively undermined my attempts to diet," admits one of my girlfriends, who has struggled with her weight since the birth of her younger son, now aged six.
"They present me with cake or brownies as though it's a great big joke, and actually cheer when I 'break' and take a bite. On one level it's funny, but on another it's mean and thoughtless."
This sort of sabotage is not necessarily conscious. Exerting peer group pressure serves to give everyone "permission" to indulge; it's about them, not you. But it's hard to resist without causing offence. As a social species, eating and drinking constitute a form of bonding and those who decline - whatever the reason - are viewed as upsetting the norm and hence the group dynamic.
Rightly or wrongly (and I'm very much on the side of wrongly), the simple act of declining alcohol in the pub or a slice of Victoria sponge in the office really does have an impact on others, however illogical.
It accounts for the causal link that emerged in a landmark 2007 study carried out at Harvard - namely, that a person's chance of becoming obese increases by 57 per cent if he or she has a friend who becomes obese in the same time period.
It's similar for siblings. If your brother or sister becomes obese, you have a 40 per cent chance of following suit. And if your spouse becomes obese, you have a 37 per cent likelihood of joining them - not because they are force-feeding you, but because partners tend to mirror each other's behaviour.
I'm as weak-willed as the next person when it comes to deciding between a couple of caramel biscuits or a piece of fruit. Unless, of course, there are no biscuits, in which case I will eat the apple - but only once I've investigated to see whether there's a jar of Nutella in the cupboard and a clean teaspoon in the drawer.
For most of us, eating healthily at every meal, every day, is hard. Even managing five portions of fruit and veg daily can be a challenge.
In January, a review commissioned by the World Health Organisation found that people who get plenty of fibre cut their risk of early mortality by up to a third. They also reduce the risk of heart attack, stroke, type 2 diabetes or bowel cancer by up to a quarter.
Yet the vast majority of adults in Britain - about 91 per cent - eat less than the recommended daily amount of 30g of fibre a day. Women eat just 17g on average and men 21g.
So what's the answer? That's a rhetorical question, because we already know. Ditch processed foods. Embrace leafy green veg. Eat brown rice and pasta. Legumes. Unsalted nuts. Fruit. Drink more water.
Moderation doesn't make for the sexiest of menus, but frankly now that Death by Chocolate is less a pudding and more a premonition, our fate lies on our plate. Saboteurs bearing sponge cake can just fork right off.
The Telegraph, London