The new rules of lasting weight loss in 2023, it’s pretty simple: eat less and move more. But first, figure out what your ideal weight should be – though don’t pick a random number on the scales or force your body to fit into an unrealistic ideal sold to you via Instagram. Instead, try (harder) to love and accept your body  (that’s body positivity).

Oh, and have you tried intuitive eating?

After decades of being told how, when and what we should eat, Australia still has a massive weight problem. Two in every three adults in this country are overweight or obese, and less than seven per cent of us eat a healthy diet. Is the confusing advice to blame? Absolutely, say a bunch of experts who are fed up with the out-of-date messages of toxic diet culture.

“We’re becoming more and more obsessed with being thin… as we get fatter and fatter,” says Glenn Mackintosh, a psychologist and author of Thinsanity. “The craziest part is most weight-loss ‘solutions’ are part of the problem.”

He’s part of a growing group of doctors, nutritionists and weight psychologists who have moved beyond some of the outdated ‘truths’ that persistently hang around, like that juice-fast-cleanse book you’ve never been able to bin. If you want to truly change the way you eat, they say it’s time to go back to weight-loss school and unlearn everything you’ve been told about having a healthy body. Ready?

New rule 1: There are no ‘bad’ foods

Putting any foods on the banned list is now passé. Yes, even foods like processed meats and those cheese fries that are more cheese than potato. A sure-fire sign you’re on a ‘diet-in-disguise’ is if you’re referring to food as ‘good’ or ‘bad’, says Lyndi Cohen, a dietitian and author of Your Weight Is Not the Problem.

“Sugar and saturated fat are not the enemy. You do not need to detox. One thing you can do starting today is updating your food language,” she says. “Remind yourself: ‘I don’t need to be perfect in order to be healthy.’”

As one of Australia’s most vocal anti-diet advocates, Cohen believes that dieting itself is outdated. “Diets increase cravings for the very foods you’re trying to avoid, slow down your metabolism and make you more obsessed with eating. If you want to eat healthier, practice ‘crowding’ where instead of creating a list of foods to avoid, focus on the foods you’d like to eat more of in your diet. Naturally, you’ll crowd out the less-healthy foods with more nutritious options, without feeling deprived.”

New rule 2: BMI is BS

The Body Mass Index (BMI) is a formula use by everyone from your GP to the World Health Organization to divide us all into some neat-sounding boxes. Calculate your weight in kilograms by your height in metres squared, and you’ll get a number. Below 18.5 means you’re underweight, between 18.5 and 24.9 is normal, 25 to 29.9 is overweight and above 30 is obese.

The problem with BMI is that it’s flawed, according to many experts. And also racist, say others. Invented in the 1830s by Belgian statistician Lambert Adolphe Jacques Quetelet, BMI ignores waist size (one indicator of health) and makes no allowance for the proportions of bone, muscle and fat in the body. It was also develope as a measure of ‘ideal weight’ for white European men, and many say it’s not always an accurate depiction of health for other demographics and races.

“BMI isn’t a useful measure of health,” says Cohen. “Old-school nutrition will tell you that you need to fall within the ‘normal’ weight range, but BMI doesn’t consider muscle mass, diet quality, mental wellness, sleep quality, fitness or any other metric.”

So how do you figure out if you could stand to lose a little weight or your body is fine as it is? “There are many [other] scientifically valid ways to measure health, such as checking in on your blood pressure, cholesterol, fitness or blood-sugar levels,” says Cohen.