Science has popped the bubble of soft-drink addicts whose new-year health resolution was to switch to diet beverages. You might as well chuck money pointlessly at a gym membership like the rest of us, say researchers (I’m paraphrasing).

A review this week by Imperial College London and two universities in Brazil found no evidence that artificially sweetened drinks help people lose weight.

The researchers suggest this is because people think that a halt to drinking sugar is a licence to eat more cake, in the same way that we might delude ourselves that if we take a multivitamin, we can get away with living on Kettle Chips. There is also evidence that sweeteners make us hungrier and crave more sugar. But this is far from the only red herring that might lead to disappointment in the weight-loss stakes.

Anything with artificial sweeteners

They may make food and drink taste nice, but they can’t trick the brain’s reward centre (or pleasure centre), which knows it didn’t get the full hit, leaving you unsatisfied and wanting to sniff out the real thing. The taste without the calories isn’t good enough for a sugar-indoctrinated brain.

Healthy treats

Some scientists refer to this as the “halo effect”. Slap an organic label on a chocolate chip cookie and people will think it’s healthier and more nutritious. It isn’t. And while the calories in an oaty raisin cookie may be less empty than those in a triple-choc, oat-free version, be under no illusion: it’s the sugar that keeps you coming back for more.

Sugar is, of course, the devil; the more we eat, the more we crave, the less energetic we feel and the larger we grow.

Low-fat diets

Thank goodness someone finally cottoned on that, when it comes to fat, things aren’t that simple. It may have a few extra calories, but we will all perish without it. (Let’s hear it for good fats in oily fish, nuts and seeds.)

What’s more, mass-produced low-fat products tend to compensate by adding more of the real devil: sugar. But health aside (many are more motivated by the aesthetics of a beach body than boring old health anyway), low-fat diets won’t make you as thin as low-carb or olive-oil-drenched Mediterranean diets.

Exercise

God, this one’s a bummer. You start hauling your ass around the park or a cardio and weights circuit, and feel really good about yourself for a while, only to discover after a few months that you look pretty much the same. There’s only so long you can dismiss your unchanging weight with the adage “muscle is heavier than fat”.

Studies have been struggling to link exercise alone and weight loss for a while now, and one hypothesis as to why, published last year, is that energy expenditure doesn’t necessarily correlate with activity levels. Seems weird, but now the scales have fallen from our eyes regarding fat being the devil, anything goes. Also, exercise makes you hungrier.

However, nothing works in isolation when it comes to health, and there’s no denying that exercise makes you fitter and stronger and happier and healthier, and these things could just spur one on to eat that elusive healthy, balanced, diet that sensible people seem to agree is necessary.

New Year resolutions

January just isn’t the right time start a punishing regime. Yes, an extra-healthy week to recover from Christmas excess feels good, but it’s just not feasible. It’s freezing, it’s dark, everyone’s hibernating to avoid alcoholic temptation, plus animals are hard-wired to lay down fat stores to get through winter. Even though we don’t need extra energy in winter any more, because we have clothes and transport and heating, our stupid genes haven’t caught up.

“All animals, including humans, should show seasonal effects on the urge to gain weight,” says Dr Andrew Higginson, a senior behavioural science lecturer at the University of Exeter. “Storing fat is an insurance against the risk of failing to find food, which for pre-industrial humans was most likely in winter. This suggests that New Year’s Day is the worst possible time to start a new diet.”

But don’t let all this put you off. Weight loss studies are always limited in that we’re all unique, and there are so many variables. And they’re always after population-wide effects, rather than things that work for a few people but don’t work for a few others. There are exceptions to every rule.

In this spirit, let us give the last word to a commenter who posted beneath the Guardian’s news report on the diet-drinks study. “Since switching from Full Sugar Pepsi (11%) to low sugar R Whites lemonade (2%) I have lost 3 stone.”