The food industry has helped push the belief that people's sedentary lifestyles are solely to blame for widespread obesity, three researchers argue in a new editorial. 

And by doing so, the industry has deflected attention from the role that sugary drinks and junk food play in making people fat, said Dr. Aseem Malhotra and his colleagues. Malhotra is an honorary consultant cardiologist at Frimley Park Hospital in the United Kingdom and science director of the advocacy group Action on Sugar.

"The public health messaging around diet and exercise, and their relationship to the epidemics of type 2 diabetes and obesity, has been corrupted by vested interests," the researchers write in their editorial, published today (April 22) in the British Journal of Sports Medicine. They liken the food industry's tactics to those that "Big Tobacco" used to obscure the link between cigarettes and lung cancer.

But, more controversially, Malhotra and his colleagues also state, "Physical activity does not promote weight loss."

Other experts disagree.

There is a difference between "physical activity" and "exercise training," said Gordon Fisher, an assistant professor of nutrition at the University of Alabama at Birmingham. Both burn calories, but physical activity consists of nonstructured activities, such as gardening or walking the dog, whereas exercise means planned, structured and repeated activities, such as weight training or running.

"While this may seem like a minute point, it is critical" in discussions about whether physical activity or exercise are effective in helping people lose weight, Fisher said. [How Many Calories Am I Burning? (Infographic)]

Supervised exercise training can help people lose weight, but most people don't engage in enough physical activity to promote weight loss, he told Live Science.

So, although Fisher said he sees some truth in Malhotra's argument that the role of exercise in weight loss has been overblown, "there are many studies that demonstrate the benefits of physical activity on energy balance and the prevention of weight gain."

There is no doubt that poor diet has contributed greatly to the obesity epidemic, Fisher said. But "physical inactivity plays an even larger role" in aggravating the health conditions — such as insulin resistance, and hypertension — that can accompany being overweight, Fisher said.

James O. Hill, director of the Center for Human Nutrition at the University of Colorado in Aurora, said that the food industry certainly bears some responsibility for the current obesity epidemic, and should be involved in addressing it. But it's simply wrong to say that physical activity doesn't promote weight loss, he said.

"They're ignoring not just thousands, but tens of thousands of articles showing the importance of exercise for weight control," Hill said. "I think it's a disservice to the science of exercise physiology."

Hill said that what he calls the "inactivity industry" — companies that suck people into spending so much time on screens — is also to blame, and should take steps to help tackle obesity, too. "Bill Gates has probably caused as much obesity as junk food," Hill said.

"We've got to quit debating whether it's diet or physical activity. We have to do both."

Malhotra did not respond to emailed questions by press time.

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