Coles Simply Less is a range of 90 products aimed at "health conscious" customers - its marketing claim is that it "won't hurt the hips, or the hip pocket". It joins established brands McCain Healthy Choice - which has more than 30 products -and Lean Cuisine, with its 35-plus meals. Weight Watchers – with a whopping 230 supermarket products – has teamed up with brands such as cheesemaker Bega to market products with "Approved by Weight Watchers" and the number of Weight Watchers 'Points' printed on the packaging.
Although these brands don't use the words "diet" or "weight loss", their packaging does display terms such as "guilt-free", "lean", "balanced", "healthy", "less" and "stay in shape", which are likely to pique the interest of dieters. There is an emphasis on fat content, kilojoule counts or, in the case of Weight Watchers, the Points value of foods.
Can diet foods aid weight loss?
The good news
Many diet products tend to be highly processed, salty, sugary treat foods with little nutritional value. From jams and biscuits to salad dressings, they're foods you'd assume a dieter should avoid, even with reduced kilojoules. So do these products have a useful role as part of a balanced diet of fresh fruit and vegetables, wholegrains, lean meat and low-fat dairy?
"Diet foods can provide a less harmful alternative for people who are dedicated to losing weight, particularly if they're looking for a treat," argues Professor John Funder, executive chair of Obesity Australia. There's good data, he says, to show that if people know upfront how many kilojoules they're eating, they can end up eating about 200kJ fewer across a day.
The bad news
Nutritionist Dr Joanna McMillan agrees that diet foods can "hold your hand" while you're trying to lose weight – being able to swap your favourite rich foods with "diet" versions means you don't have to go cold turkey on treats - but she believes they can also lull dieters into a false sense of security.
"People may think, 'I've eaten something low kilojoule, so I've got some credits to eat something extra', and they end up overeating," she says. "Strict kilojoule counting is not always a practical, healthy option, and women in particular can be obsessive about it – and this can be in addition to a poor body image and the habit of swinging between loving and hating food."
Choosing foods purely based on their kilojoule content doesn't take into consideration the nutrients present in the food. A low-fat rice cracker may have fewer kilojoules than a handful of nuts, but the latter is a better choice nutritionally, and will help you feel fuller for longer.
McMillan prefers what she calls "kilojoule awareness". By all means check the nutrition panel of a product for the kilojoules and see how it fits into your daily intake, she advises, but focusing obsessively on a rigid kilojoule-controlled diet doesn't help people learn how to respond to hunger signals or make consistently healthy food choices.
How many kilojoules should you have?
"Dieters should eat no less than 5000kJ a day, otherwise you run the risk of missing out on the nutrients you need and end up starving and unhappy," says McMillan. "A main meal should be about 2000kJ and a snack 600kJ.
The Coles Simply Less website offers some sensible weight-loss tips, but its daily meal plans are high in Coles packaged products and low on fresh fruit and veggies. The main meals are very low-kilojoule (dinner 1477kJ), and on one day of the plan, almost a third of the kilojoules were made up of snacks or desserts such as chips, custard and brownies.
"Although you'll lose weight on a strict diet of low-kilojoule products in the short term, it's not sustainable," says McMillan. "To keep weight off, you're better off joining a program and/or working with a dietitian to learn how to eat to maintain weight in a healthy way."
"If you consistently shave 600kJ off your daily kilojoule intake and exercise, you'll lose weight over time," says Professor Funder. Eating smaller portions is one way to achieve this.
A study published in The Journal of the American Dietetic Association found the bigger the portion size on offer, the more people ate. And, although test subjects reported feeling fuller, they didn't eat less at the next meal to compensate, leading to significantly increased energy intakes.
On the flipside, a study of 300 obese and overweight adults found those who spent the most time controlling portion size during their weight-loss and maintenance efforts were more likely to lose weight compared with those who focused on increasing physical activity, reducing fat in their diet or eating more fruit and vegetables.
Serving size deception
While portion size is how much actually ends up on your plate, the "serving sizes" on nutritional panels are recommendations determined by food manufacturers. Serving sizes can swing between unrealistically small and obesity-inducing large serves, and some products may have more serves than you'd reasonably expect in a packet.
For example, Smith's Potato Chips Thinly Cut Sour Cream & Onion 175g packet has 3763kJ. The recommended serve size totals 581kJ – sounds OK for a snack, until you realise a serve is a laughable 27g (or about 18 chips). And there's an unwieldy 6.5 serves per packet. In contrast, Coles Simply Less Sweet Chilli & Sour Cream Potato Snacks come in a more realistic 40g pack with 760kJ, which compares favourably with a 45g packet of Smiths Thinly Cut, which has about 981kJ.
Always consider the size of the packet, how much of it you'll eat, and the kilojoules per 100g, rather than the serving size.
One method of having your cake and not eating too much of it is to buy your "sometimes foods" in pre-packaged portions – something diet food brands can do well.
"Along with knowing how many kilojoules are in a product, it's been shown that smaller, controlled portions can help shave kilojoules off your daily intake," says Funder.
As an example, a sensible portion of Cadbury Light Vanilla Ice Cream is 50g (one scoop) and has about 330kJ. But stopping yourself at one scoop is easier said than done when there's a tub of ice-cream on your kitchen table looking longingly up at you. This is where the controlled portions come in.
Cadbury Light Vanilla Ice Cream: 330kJ per 50g (one scoop), 19c
Skinny Cow Vanilla Chocolate Ice Cream Stick: 340kJ per 67g, $1.05
Weight Watchers Creamy Vanilla Ice Cream: 422kJ per 74g pack, $1.90
Diet foods 101
"Low fat!" is a favourite badge on branded diet food packaging, but this doesn't necessarily mean it's a healthier choice for weight loss. The low-fat trend started as a way of reducing kilojoule counts in foods, but sugar, salt and/or refined starches (white flour, white pasta, white rice) are often used to replace the flavour of fat.
"Fat in food slows down the rate of food leaving your stomach, and so can help keep you full for longer," says McMillan. "Fats also carry fat-soluble vitamins, and many antioxidants, including beta-carotene, need fat to be absorbed. But you do need to be careful about which fats you include in your diet.
"Think about what your ancestors ate before processed foods – they ate fat as part of natural foods such as avocado, nuts, seeds, olive oil, oily fish and animal foods. Many fats in the modern diet come from refined oils and fats used in processed food products, and these are the ones to limit."
It's common for diet products – in particular yoghurts and ice-creams – to reduce kilojoules by using artificial sweeteners. Products often boast they're "97% fat free" and have "no added sugar", but tend not to shout out that they're artificially sweetened. So if you don't like the idea of artificial sweeteners you'll need to check the ingredients list.
Weight Watchers has a novel way of reducing kilojoules in its "no added sugar" peaches. Instead of juice or syrup, the fruit comes in water sweetened with cyclamate (additive 952) and saccharin (954), an artificial sweetener used in Sweet'n Low. This reduces its kilojoule load to 109kJ per 100g compared with 261kJ for the Goulburn Valley Peaches in juice.
Coles Simply Less Dark Chocolate has 357kJ per 20g bar compared with 425kJ for a 20g bar of Coles Dark Chocolate. But its main ingredient is maltitol, a sugar substitute that can have a laxative effect if eaten in excess.
"Diet ready-meals are more nutritionally balanced than they used to be," says McMillan. "However, the serves are small in order to keep the kilojoule count down, so they may not fill you up enough or keep you full for long, and you may find yourself reaching for a snack soon after."
McMillan says it's preferable to eat food with a low energy density such as salads, vegetables or legumes, along with a small serve of lean protein, because you can eat lots of these foods for the same amount of kilojoules compared with highly processed ready-meals. They're also digested slowly, keeping you feeling full for longer, and provide a range of beneficial nutrients you won't find in those meals.
Although the diet lasagnes we looked at generally have less sodium than regular lasagne ready meals, the sodium levels are still very high. McCain Healthy Choice Beef Lasagne and Coles Simply Less Beef & Vegetable Lasagne contain 880mg and 900mg respectively per 400g serve. (The current advice in Australia is for adults to consume less than 1600mg per day.)
"A better choice than a takeaway, these diet ready-meals should be reserved for an emergency – when you come home starving or are in a hurry," says McMillan. "And bulk it up with a quick salad or side of mixed veggies from the freezer."
Counting kilojoules and dollars
Do diet products actually have fewer kilojoules than regular products? Well, yes and no. We found some products have significantly fewer kilojoules compared with regular items, while others have more. So before reaching for diet brand products purely for their kilojoule count, spend some time comparing the nutritional panels.
Weight Watchers Fruit & Fibre Tropical: 755kJ per 50g
Uncle Tobys Plus Fibre Apples & Sultanas: 715kJ per 50g
Coles Simply Less Thin Rice Cakes: 224kJ per 2 cakes
Sun Rice Thin Rice Cakes: 196kJ per 2 cakes
In our analysis, we found that you can end up paying extra for diet or "healthy" brands that are nutritionally almost identical to "regular" brands. For example:
Weight Watchers Cottage Cheese: $4.07 for 250g / 381kJ per 100g
Dairy Farmers Low Fat Cottage Cheese: $3.49 for 250g / 389kJ per 100g
Just like any other food that comes in a package, careful scrutiny of a diet food's nutritional panel is essential. Don't assume that just because a food is part of a range of branded diet products it has fewer kilojoules, less fat or sugar, or is a healthier choice – and you may end up paying more for it than a regular product.
Although they can be tempting for a quick weight-loss fix, McMillan doesn't recommend these highly processed supermarket diet foods as part of a weight-loss regimen. At best, says McMillan, they may be helpful for some people, but only as part of a sustainable, long-term food and exercise strategy.