KICK THE CAN

Your diet drink habit is harmless enough, right? Don’t be so sure

Picture the scene: lunch has come and gone and, in offices across the land, Tupperwares once home to prepped-ahead sweet potato, chickpeas and spinach lie empty. The temptation to attack the office tub of M&S mini brownies is oh-so real. But rather than blow a few hundred calories on a handful, women nationwide reach instead for ‘guilt-free’ cans of chemically sweetened carbonated liquid. Are they hypocritical self-saboteurs for following healthy, totally ’grammable meals with a diet fizzy drink? Perhaps – which makes it all the more tricky to admit I am one of them. A health writer who knows her nutrition – and should know better – but can’t get enough of the stuff. Another is journalist Georgia Scarr. Glance at her Instagram and you’ll see all the healthy-girl hallmarks. Bird’s-eye view of eggs atop kale and roasted veg? Check. One lithe, toned body contorted into impressive yoga positions? Check again. But one lifestyle ritual that doesn’t make the edit is her diet cola habit. ‘I have a sweet tooth, but I don’t make a habit of eating junk food,’ she says. ‘I monitor my calories, and I want them to be from nutritious food and drink, not sugar. But then the craving for something fizzy hits. I know diet drinks aren’t good for me. I can’t say I’m proud of my habit.’ The enduring appeal of calorie-free fizzy pop might jar with the current ‘it’s a lifestyle, not a diet’ healthy-eating zeitgeist, but Jane Ogden, professor of health psychology at the University of Surrey and author of The Psychology of Eating, isn’t surprised. ‘So-called “diet” drinks still appeal because, though people may package it as “eating

well” or “looking after yourself”, many of us are essentially still dieting.’ And while our goals may be more rippling abs than thigh gap, she is right in that the majority of us want to keep our body fat low. ‘The word “diet” carries powerful connotations of being lean, healthy and in control,’ Professor Ogden adds. ‘So while we continue to aspire to those things, “diet” labelling will draw us in – even if we’d rather not admit it.’ Put in those terms, our fondness for diet drinks doesn’t seem so incongruous. But is cracking open a can actually helpful when you’re trying to get – and stay – lean? Bosses at Slimming World appear to think so. The organisation (which has over 900,000 members in the UK) classifies diet colas as a ‘free’ food, meaning that its members don’t have to track how much they consume. Yet when you take a look at the evidence, this permissive attitude to drinks sweetened with chemicals such as sucralose and aspartame could be far from helpful. In one study, published in the American Journal of Clinical Nutrition, scientists found that participants who drank one litre of a diet fizzy drink daily gained 1.5kg after six months. The group who drank full-sugar soft drinks gained 10kg. So the diet option had less of an impact, sure. But why did the diet-drinkers gain any weight at all, given these drinks are calorie- and sugar-free?

MIXED MESSAGES

As it stands, there’s no evidence-based answer. But Robert Lustig, professor of endocrinology at the University of California and anti-sugar campaigner, has a possible explanation – essentially that consuming artificial sweeteners can significantly alter your biochemistry and predispose you to gaining fat. ‘The diet soft drink group gained weight not because they were increasing their calories, but because their insulin levels had risen,’ he says. Insulin is a hormone that allows your body to use sugar (or glucose) from carbohydrates, or store it for future use. ‘The more insulin you have in your blood, the more calories you’ll store as fat,’ adds Professor Lustig. ‘So anything that raises insulin will make you gain weight.’ Because they don’t contain any actual sugar, artificially sweetened drinks shouldn’t technically spike insulin. But, in one study in the journal Diabetes Care, researchers split their study participants into two groups and supplied half with a diet soft drink. They then tested their glucose and insulin levels afterwards and found 20% more insulin in the blood of those who’d drunk the fake

sugary drinks than those who hadn’t. Why? It’s all down to the fact that the body is primed to detect sweetness. So, when something sweet hits your tongue, specific receptors are triggered. ‘First, they send a message to the brain to say that sugar is incoming,’ explains Professor Lustig. ‘Then the brain sends a message to the pancreas telling it to expect the sugar, so it prepares to release insulin.’ But when you drink an artificially sweetened drink? The sugar never comes and the pancreas sends out the message that you need to seek out more glucose.

SUGAR: FIXED?

Yasmin, 25, consumes several cans of diet fizzy drinks a week to help her stick to a ‘no-sugar lifestyle’. ‘It means I can have the sweet taste without consuming any actual sugar,’ she says. Down 2st, wearing jeans for the first time in years, and hitting the gym for strength and cardio sessions four times a week, Yasmin is steadfast that she’ll maintain her methods. ‘If these drinks help me stick to a plan that works, I don’t see it as a problem.’ But Professor Lustig warns that Yasmin may be making life hard for herself. ‘Drinking artificially sweetened drinks when you’re not eating real sugar is self-defeating,’

‘IF DIET DRINKS HELP ME STICK TO A FITNESS PLAN, WHAT’S THE PROBLEM?’

he says. ‘The point of a “no-sugar lifestyle” is to desensitise yourself to sweet foods, but if you’re regularly consuming sugar-free fizzy drinks, then you’re re-sensitising yourself.’

THE BOTTOM LINE

So, the jury’s out on whether slimmers should sip so freely – and there is still much we don’t know about how artificial sweeteners are linked to disease risk, too. While a recent study did show that people who drank diet drinks had an increased chance of developing cancer or strokes, lead author Dr Matthew Pase cautions that this is early research – so it’s impossible to gauge cause and effect. As for claims that sweeteners such as aspartame could cause cancer? ‘The balance of evidence is that artificial sweeteners are safe for us to consume,’ says clinical dietitian Rick Miller. ‘Some experiments on mice demonstrated a link between aspartame and the growth of cancerous tumours – but it is not clear if we can directly relate these results to humans.’ Miller’s message for us habitual drinkers? Don’t freak out, but do cut down – on all fizzy drinks. ‘Regular and diet varieties contain phosphoric acid, which research suggests can reduce bone mineral density,’ he says. And let’s be clear – a stress fracture caused by weak bones is going to have a worse effect on your aesthetic and athletic goals than a few mini chocolate brownies. Still, I can’t promise that I won’t have had a sneaky sip of my old poison by the time you’ve read this. But if I do choose to crack open a can, it certainly won’t be done mindlessly. Because, while a part of me may still be sold on the zero-sugar, zero-calorie promise, there is a big chance that my body is not.