True or false: "Slashing carbs from your diet is a great way to accelerate your metabolism and lose weight"? If you followed the received wisdom of recent years and said true, you risk failing the "Metabolism IQ test" in the September issue of Shape: "Those self-proclaimed diet gurus can see you coming a mile away. Time to get savvy," it advised, "now!"

One particular weight-loss method has been in the news recently, and so Slimming (September) asked its readers to give their views on the high-protein, low-carbohydrate Atkins diet. Despite getting bad breath and constipation, one reader was delighted to lose almost four stone over six months - though he also admitted to taking up exercise and cutting out beer. Another, however, suffered severe headaches and shed only two pounds: "It was really difficult to go carb-free at a lot of restaurants," complained 25-year-old Emma Dixon. However, she said, she was sure it worked.

Slimming World (August/September) contented itself with a general sniff at fashionable diets. "It's not surprising that new theories about weight gain are seized on by the press. And when endorsed by celebrities, they become the latest slimming miracle." The magazine had its has own secret formula, the Food Optimising System, which is written in the arcane language familiar to frequent dieters: "You can eat foods in green on a Green day and foods in red on an Original day freely ... Each day, choose around 10 Sins' worth of food ... from the Sin selection list." Clear about that?

Every diet magazine tries to inspire its readers with tales of slimmers who found the thin self within. So Slimming World boasted that the Food Optimising System helped Anna down from a size 28 to 12 (she had worried she wouldn't fit on the plane taking her on her dream holiday). Loyally, she sent in her "weight report card" every week and went to Boots to be weighed. "I've still kept my weight slips because they're a reminder of what I've achieved," she said. And Slimmer (September) reported that "determination and a love for life helped Margaret Stone lose her namesake four times over."

If stories - and puns - like that don't get you on the treadmill, the magazines were full of helpful motivational psychology. "In your mind's eye imagine you're looking up at a blank cinema screen," suggested Slimming World. "Be your own film director and on the screen, see yourself in the future ... Have fun by choosing a soundtrack. Is it pop, classical, jazz or your favourite love song?"

Anyone who still finding it hard to keep their fingers out of the hors d'oeuvres should get themselves a manicure, said Weight Watchers magazine (August/September): "People always notice well-groomed hands, plus it's difficult to eat while your nails are wet!"

And if you simply must eat, you should visit the website Caloriecounting.co.uk, as recommended by Slimmer, where you can calculate your body mass index, a measure of how overweight or underweight you are. Shape was also exhorting its readers to log on to lose weight: "Spending just a few minutes or so a week reading emailed nutritional advice can help you change your eating habits," it said.

All the magazines also did their very best to make diet plans seem like gastroporn for the healthy, offering pages of sumptuously photographed dishes and the recipes for them. WeightWatchers even gave its readers pictures of the foods you can only eat in moderation, with a feature on the food purveyed by the big burger chains and their WeightWatcher scores. Did you know, for example, that you use fewer points eating a Wimpy's Classic Hamburger than its Quorn in a Bun? No?

Time now to retake the Shape test."You're totally revved! No chance anyone will be pulling the wool over your eyes when it comes to goofy metabolism or diet claims."