On the face of it the cause of weight gain is simple: we eat too many kilojoules.
What's less simple is fixing the reasons that encourage overeating - a complex mix of factors like the need for comfort, the power of food marketing and inflated portion sizes, none of which have anything to do with hunger.
On top of this is a food supply loaded with amped up flavours that make it easy to overeat.
Traditional foods that used to be simple now come with extra layers of flavour and kilojoules - plain yoghurt has been almost kicked out of the chiller cabinet by sweetened yoghurt; scones and hot cross buns come flavoured with chocolate, there's pizza made, not just with cheese and ham, but ham and bacon and pepperoni and barbecue sauce - and we're embellishing a cup of coffee with caramel syrup.
It's what Dr David Katz, director of Yale University's Yale-Griffin Prevention Research Centre in the US, calls the hidden challenge to eating well in the modern world.
This over-flavouring of food can be hard on the waistline, says Katz, explaining that we're hardwired to crave sugar and salt, a hangover from our hunter gatherer days when sweet, salty or fatty foods were hard to find but important for survival in a time when the food supply was unpredictable.
But what was once a survival advantage in an age when the only sweet foods were breast milk, honey and fruit makes us easy targets for an industry flogging food with more-ish flavours.
"Manufacturers of processed foods are counting on this," Katz says. "Their goal is nothing short of wanting to profit from our inability to control ourselves when their irresistible food product is in our hands."
We're not entirely helpless though.
Reliance on very sweet and salty flavours is reversible and in Disease Proof, a new book that provides practical skills for preventing chronic disease, Katz devotes a chapter to retraining overstimulated taste buds so that we can appreciate the natural flavours of healthier foods, widen our food preferences and tame food cravings.
It starts with cutting down on added salt and sugar by reducing reliance on processed foods.
Making foods like pasta sauce or salad dressing at home rather than buying them off the shelf, for example, gives us more control over the ingredients and flavours we consume.
It also helps to get to know the different names that sugar hides under on the labels of packaged foods such as sucrose, fructose, maltose and lactose. (Katz also fires a shot at one sweetener with a health halo - agave syrup which he describes as a highly concentrated source of fructose with little, if any, health benefits even though it's promoted as a healthier option to sugar.)
"Your taste buds will adjust to lower thresholds of these flavours, feeling satisfied with lower amounts of sugar, salt and fat," he says.
"Over time, the sweet and salty flavours you used to eat by the handful may taste too sweet or salty."
As for food cravings, these are less likely if you eat healthy meals and snacks at regular intervals to keep hunger under control, says Katz who also points out that - like nicotine cravings - a food craving will often pass if you can wait it out for a few minutes.
"Research from the University of Exeter in the UK found that a 15 minute brisk walk reduced urges for chocolate among regular chocolate eaters. If you must give in to a craving, have a small portion, then wait.
"Researchers at Cornell University recently found that hedonic hunger (eating for pleasure) is satisfied by a handful of a tasty food and tends to disappear after 15 minutes so long as the memory of indulgence remains," he adds.
It's also possible to tame cravings with healthier foods - if you want something sweet, try something naturally high in sugar like fruit, or try turning the sweet craving off by eating something with a sour or palate cleansing flavour like citrus or mint.
Speaking of sour flavours, Katz also points out that some of the healthiest foods on the planet - like kale, grapefruit, spinach and plain yoghurt have a naturally bitter flavour and if we shun them we miss out on their benefits.
His tips for making them easier on the tastebuds: sweetening the flavour of Brussels sprouts or broccoli by roasting them with a little olive oil to bring out the natural sugars in these vegetables; serving sautéed kale with a little balsamic vinegar and mixing berries and a dash of vanilla extract into plain Greek yoghurt.
- Sydney Morning Herald