Main menu


which works best for weight loss? Science has the answer. But it's complicated.

featured image

Magda Szubanski knows she is overweight. She has tried to eat less and move more. Because that’s what society says to do, and because she is “not a stupid person”.

“It’s not that I lack willpower,” she tells the Green Guide. “And it’s not that I lacked shaming and nagging my whole life about it. None of those things have worked for me, and I doubt very much that they work for anyone.”

Magda Szubanski hopes Big National Health Check will lead to more open conversations about why people are overweight.

Magda Szubanski hopes Big National Health Check will lead to more open conversations about why people are overweight.

Her new TV series, Magda’s Big National Health Check, explores the damage done by “diet culture” and the limits of individual responsibility for health problems.

It’s telling, then, that when she asked on Twitter why fat people were not protected from vilification, the response was sudden and savage.

“Lose some weight then,” wrote one account. “Because you choose to be fat,” yet another wrote. “Being fat is a choice,” wrote a third.

Many members of the public have come to believe that being fat is a choice, one made by eating badly and not exercising enough. But scientists hold a radically different view. Over the past decade, the science – and the blame – has dramatically shifted focus.

“The obesity epidemic’s root cause isn’t individuals going, ‘I’m going to lie on the couch and eat delicious food’,” says Jane Martin, president of the Australia New Zealand Obesity Society. “What’s happened is people are being shaped and nudged every step of the day.”

Rather than individual choice or a collective collapse in willpower, modern science points to the effect our environments have on warping our food and exercise choices – away from health foods and towards highly processed, highly profitable junk. Some scientists are skeptical we are truly making “choices” at all.

And there’s growing recognition that treatments that focus on the individual, such as diets, are not the full answer.

Big corporations love to put it back on the individual.

Jane Martin

The “individual choice” narrative does follow one group in particular, says Martin: food companies, which have spent years pushing it. “Those big corporations love to put it back on the individual,” she says. “It suits them, because where are the solutions? Not with the individual, but with government.”

Melbourne-based artist Erin Cox has an upcoming exhibition called A(Di)pologyexploring society’s expectation that fat people should apologize for being fat.

“There are many facets of our society that place responsibilities only on individuals,” she says. “These agendas benefit not the individual nor the collective – but wallets.”

Fundamentally, obesity is caused by an energy imbalance. Too much energy in, not enough energy out. “You can’t escape that,” says Professor Stephen Simpson, academic director of the Charles Perkins Centre.

This equation seems to make the cause – and cure – of the obesity epidemic simple: make an individual choice to eat less and exercise more.

But over the past decade, science has discovered this equation is far more complex than it seems.

Careful studies with double-labeled water – water marked with elements scientists can track, allowing for precise measures of metabolism and energy expenditure – show that as we exercise more, our bodies compensate by increasing our hunger and cutting our resting energy expenditure.

One study spent 40 weeks training people who did not exercise to be able to run a half-marathon. To compensate, their bodies increased the amount they ate, and at the end of the study, their resting energy expenditure was lower than when they were sedentary.

Professor Stephen Simpson says it's hard to escape the fundamental role of exercise in weight loss.  But, he says, it isn't the route to losing vast amounts of weight.

Professor Stephen Simpson says it’s hard to escape the fundamental role of exercise in weight loss. But, he says, it isn’t the route to losing vast amounts of weight.

“Now that’s not to say physical activity and exercise isn’t profoundly important for your health. It is,” says Simpson. “But it isn’t the route to losing vast amounts of weight.”

These experiments also push back on the idea we’re more sedentary as a society. A careful study shows we are just as active as people living in the 1980s. If anything, we’re using more energy to move because we weigh more. People in the wealthy, fat West use as much energy as people living in the developing world – and people who are obese use just as much as people who are not.

Nor are our genes entirely to blame.

Over the past 20 years, a new technique called genome-wide association study has taken advantage of the ability to cheaply sequence someone’s entire DNA to study the genome as a whole.

Those studies have revealed more than 100 changes across the genome that can influence someone’s body mass index; they mostly cluster in parts of the DNA linked to our brain and nervous system. Genetic variation, scientists now believe, is one of the key reasons why some people get fat and others do not.

But – and it’s a big but – these genes have not changed in the past 100 years, while our waistlines have radically expanded. A scientific consensus has emerged that what we’re seeing is an interaction between our genes and our changing environment.

“The food industries are largely following profit motives.  Which is fine, it's just those profit motives are not working for the betterment of health - and rather quite the reverse,” says Simpson.

“The food industries are largely following profit motives. Which is fine, it’s just those profit motives are not working for the betterment of health – and rather quite the reverse,” says Simpson.Credit:iStock

“A lot of what has shaped the field is the use of genetics to actually show it’s a biological problem,” says Professor Zane Andrews, deputy head of the Metabolism, Diabetes and Obesity Program at Monash University. “A lot of that requires shifting the public perception from this idea that it’s a lack of willpower to the fact it’s a biological problem, in the same way that blood pressure or cancer is.”

The answer, scientists have concluded, is not exercise or genes but consumption. We eat too much of the wrong things.

But even here, assigning blame to bad individual choices remains tricky.

“I do not think it’s the result of individual choices,” says Washington University’s Dr. Alexxai Kravitz. “Once 65 per cent of the population is overweight, it becomes very hard to say this is an individual problem.”

In 1975, 10 per cent of Australians were obese. Now the figure is 30 percent; another 35 percent are overweight. These numbers keep rising, year-on-year.

This continued growth is key. As you put on weight, you need to eat more to maintain it. If obesity was simply the result of people choosing chocolate over chard, the growth in obesity should eventually plateau.

It hasn’t. So there must be some positive-feedback mechanism going on, argues Simpson, whereas we eat more, we want to eat even more. His theory: protein. “We have a powerful second appetite for protein,” he says. Our bodies need a certain amount. If our diet is protein-poor, we’re motivated to eat more food in general to get enough protein.

And it just so happens that ultra-processed foods – junk foods – tend to be very low in protein because protein is much more expensive to make than fat and carbohydrate. And we’re eating more and more of them.

One US study of 9042 people found as people added more ultra-processed foods to their diet, the total amount of protein they ate did not change but the amount of energy they consumed increased massively.

“The food industries are largely following profit motives. Which is fine, it’s just those profit motives are not working for the betterment of health – and rather quite the reverse,” says Simpson.

Consider the humble apple, an icon of good health and packed with fiber.

Consider the apple.

Consider the apple.Credit:

Now step it through the processed-food chain, from apple to apple paste to apple juice. At each step, it becomes faster to eat, less filling, less healthy and more profitable.

This is the equation that really explains the obesity epidemic, many scientists now say.

“We live in a world with junk food ads everywhere, it’s very easily accessible, it’s often very cheap. And that is the reason we’ve got such high obesity rates,” says Associate Professor Gary Sacks from Deakin University’s Global Center for Preventive Health and Nutrition.

Highly processed foods like chips and soda have much higher profit margins than unprocessed foods like apples and pears. Added sugar in breakfast cereals is usually cheaper than the grain it replaces. Highly processed foods are easier to make, easier to ship and last longer on the shelf, so there’s less waste, says the Global Obesity Center’s Associate Professor Kathryn Backholer, “so they are highly profitable”.

Because of this, the food industry is motivated to try to get us to eat more, and more poorly, says Martin. “These foods are just chemicals, you can’t make them in your own kitchen. They have been designed for you to want more of them. And they are very, very profitable for these companies.”

From a neuroscience perspective, “choice is a mirage, absolutely” says Tamas Horvath.  “The default wiring of the brain is to promote hunger.”

From a neuroscience perspective, “choice is a mirage, absolutely” says Tamas Horvath. “The default wiring of the brain is to promote hunger.”

The industry deploys several strategies that take advantage of our basic neuroscience.

When we see food, our brains produce dopamine, which makes us hungry. The food industry has responded by filling our world with images of food to keep us in a constant state of craving.

To dial up the dopamine, marketing associates food with emotions of fun or pleasure, such as Coca-Cola’s “Open Happiness” campaign.

We are hardwired to eat more when food is abundant (to prepare us for times of famine). So, the food industry has deliberately created an abundance, filling supermarket shelves with high-kilojoule foods.

One remarkable study showed simply increasing the number of different colors of jellybeans in a pack was enough to make people eat more of them. A wide variety of choice can also overwhelm our decision-making system, making us prone to seeking instant gratification.

Yale University hunger neuroscientist Professor Tamas Horvath was in Melbourne this week for a metabolic disorders summit, hosted by the Monash Biomedicine Discovery Institute.

From a neuroscience perspective, “choice is a mirage, absolutely”, he says. “The default wiring of the brain is to promote hunger.”

Coca-Cola Bottles, Andy Warhol, 1962.

Coca-Cola Bottles, Andy Warhol, 1962.Credit:Whitney Museum of American Art, New York

Much of the food industry’s response to criticism has been to focus on the role of individual choice in obesity. Internal Coca-Cola emails show it working with sponsored researchers to present studies that focused on the role of physical activity and individual choice. In the United States, its lobby group is the Center for Consumer Freedom (“devoted to promoting personal responsibility and protecting consumer choices”).

Locally, the industry claims it is working hard to give you healthy choices. Coca-Cola South Pacific announced in 2013 it would offer more low-kilojoule options as “we all need to make sensible choices to meet our individual nutrition and kilojoule needs”. It would also help supply bicycles to local communities.

“Different products are suited to different situations and attention to serving sizes and the frequency of consuming discretionary foods are important parts of ensuring a healthy diet,” the Australian Food and Grocery Council said in a statement.

“The food industry works with governments and public health authorities to support healthy eating through the Healthy Food Partnership, and is active in helping to reduce sugar, sodium and saturated fats in the national diet through programs such as the Partnership Reformulation Program.”

That’s not good enough for Jane Martin. “What you see from the industry is it’s all put back on the individual,” she says. “This is how industry has shaped the discussion because it works for them to put the individual in the frame.”

The Morning Edition newsletter is our guide to the day’s most important and interesting stories, analysis and insights. Sign up here.