Hongkongers mistakenly believe poor diet is not the primary cause of obesity

Control of food intake is much more important than exercise when it comes to weight restriction, despite what food companies would have us believe, research shows

PUBLISHED : Saturday, 27 February, 2016, 12:00am
UPDATED : Tuesday, 01 March, 2016, 9:13am

What do you think is the main cause of obesity? If you said “lack of exercise”, you’re likely to eat more – and therefore be heavier – than someone who thinks a poor diet is the primary cause of obesity, according to a local consumer research expert.

Food companies know this misconception about obesity and capitalise on it, linking their food products to exercise, says Anirban Mukhopadhyay, a professor of marketing at the Hong Kong University of Science and Technology. He has termed this tactic “leanwashing”.

In a new paper to be published in the Journal of the Association for Consumer Research, Mukhopadhyay and co-author Brent McFerran, an assistant professor of marketing at the University of Michigan, call for government intervention to increase public awareness of the true causes of obesity, converting “exercise theorists” to “diet theorists” to help stem the global obesity crisis.

“Ordinary people should believe the right thing – poor diet is the most important factor contributing to weight gain and obesity,” says Mukhopadhyay. “The obesity crisis is worldwide and growing very fast. In 2014, a McKinsey report estimated the worldwide cost of obesity to be US$2 trillion – the same as the cost of smoking, or from all war and terrorism combined.

“In Hong Kong, in 2011, the government estimated that 39 per cent of the population is overweight, and this number has surely gone up. Obesity has great social and individual costs, and we need to believe the right thing because our beliefs guide our actions. Do not expect to lose weight through exercise. Exercise has great health benefits, but control of food intake is much more important when it comes to weight restriction.”

Mukhopadhyay says medical research points to “overnutrition” rather than lack of exercise as the dominant cause of obesity, and that it’s much more difficult to rely on exercise for weight control than diet.

Thirty minutes of hiking for a 70kg man burns off about 220 calories, for example – the same calorie reduction achieved by simply eliminating a Starbucks Grande Latte from one’s diet each day.

Further, people often reward themselves for their exercise with an indulgent treat and end up consuming more calories than they burned off, Mukhopadhyay says. People also generally overestimate how many calories they burn off in exercise and underestimate how many calories they eat.

Yet, about half the population – Hongkongers included – still believe poor diet is not the primary cause of obesity, he says. In a study published in August 2013 in the journal Psychological Science, Mukhopadhyay and McFerran conducted more than 10 separate surveys in five countries and territories.

In the first study, the researchers surveyed 254 South Koreans drawn from a nationally representative sample to indicate what they believed to be the primary cause of obesity: eating too much, not exercising enough, or genetics. Diet theorists accounted for 50 per cent of the respondents, exercise theorists for 41 per cent, and gene theorists for 8 per cent. The diet theorists had a mean BMI of 21.55 (calculated by taking weight in kilograms divided by the square of height in metres) versus 23.10 for exercise theorists, representing a difference of about 4.5kg for someone 1.6m tall.

Two of the studies were different with the survey question being open-ended. In one study, a research assistant, who did not know the researchers’ hypothesis, approached 548 people at various public places in Hong Kong. The research assistant asked respondents what they perceived to be the main cause of obesity, and recorded the first response. Diet theorists accounted for 66 per cent of respondents, followed by exercise theorists at 23 per cent, and gene/other theorists at 11 per cent.

The relationship between lay theories of obesity and actual BMI was found in all survey locations (US, Canada and France were the others), even controlling for other major factors known to affect weight, such as education, sleep deprivation, stress and medical conditions.

In two of the studies, the researchers went one step further by offering respondents chocolates to look at actual eating habits. Those who rated exercise as the main cause of obesity ate more chocolates.

However, Mukhopadhyay and McFerran also showed that this outcome could be manipulated. In the final study they had participants read a passage that either said exercise was the main factor in obesity, or diet was. Those who read the exercise passage ate more chocolates.

“This finding suggests that simply informing people that eating too much is the main cause of weight gain could impede the obesity epidemic. People’s beliefs can change in response to public health campaigns from trusted sources so public health communications should focus on getting people to reduce the amount they eat, especially of high-calorie foods,” Mukhopadhyay says.

The researchers built upon their studies with another paper published in 2014 in the California Management Review that analysed the communication and promotional activities of food businesses: packaged food (companies such as Kraft, General Foods, General Mills, Kellogg’s, Unilever, Nestle, Danone), drinks (companies such as Coca-Cola, PepsiCo), and fast food (companies such as McDonald’s, Burger King, Yum! Brands).

The researchers unveiled a multipronged effort by the food businesses to deflect attention from bad diet to exercise (and other factors) as the causes of obesity, because of a vested interest in discouraging their customers from becoming diet theorists.

“Major food companies spend a lot of effort and money trying to make people believe that obesity is not caused primarily by poor diet – we called this ‘leanwashing’,” says Mukhopadhyay.

In their forthcoming paper, the researchers look at the whole obesity crisis as a case of market failure, and analyse possible remedial actions.

“We conclude that strong government action is necessary for the worldwide obesity epidemic to be arrested,” Mukhopadhyay says.

“For this to happen in a democratic society, there needs to be a widespread understanding of the problem, its causes and potential solutions. This requires a broad public debate rooted in medical science, an understanding of the relevant evidence regarding consumer behaviour, and business logic, rather than ideological positions and vested interests.

“Our analysis shows that the actions likely to be most effective, such as steep taxes and outright bans, are also the most likely to be lobbied against and therefore least likely to be implemented. Therefore, there needs to be much greater public awareness of the scale and scope of the problem.”

Correcting lay beliefs about obesity would be a start.