Who should we take health advice from? Book excerpt from ‘Change: How To Make Big Things Happen’ by Damon Centola

In 2017, two social scientists from Stanford University, Lauren Howe and Benoit Monin, wanted to find out how to make health messages from physicians more effective. For decades, marketing firms have relied on the popular idea that medical experts are the most influential people for spreading health-and-lifestyle changes. If a physician wants you to try a new diet, they would be most convincing if they were to model that behaviour themselves.

But for an obese patient, a healthy physician who advertises the merits of exercise by discussing their personal routine is not in fact likely to be an effective source of influence. In fact, this role-model strategy can backfire: Howe and Monin found that less healthy patients feel judged — even devalued — by physicians who advertise their own healthy lifestyles. The unintended effect is to make patients less receptive to medical advice regarding changes to their diets and exercise habits.

When people need to be convinced that a new behaviour or technology will be useful for them, the most influential contacts are typically people who resemble them. In the diet-diary study, for example, obese participants were far more likely to adopt the innovation when they learned about it from similarly overweight peers. For them, less healthy people were more relevant sources of influence than highly fit ones.

I once attended a lecture by a world expert on the topic of obesity. He presented a chart of height-to-weight ratios and asked the audience to find themselves on that chart. He then proceeded to lecture them on the problem of obesity in the United States, and the changes that most Americans needed to make to their diets.

Afterward, my colleagues and I stood silently in the lobby. Finally, someone spoke. “I have never felt so defensive in my entire life,” he said. “All I could think about was how skinny that lecturer was.” We burst into a chorus of agreement.

My colleagues and I were all recent PhDs. All of us were young, athletic, and fit. In fact, my colleague who spoke up was a runner who had been a competitive athlete all through college and graduate school.

It didn’t matter. Nor did it matter that we were all working on health-policy research at the time; somehow the lecturer had made us all feel self-consciously different from him. None of us could even remember the main points of the lecture. All we could think about was how offensive it was. (And how much we suddenly felt a craving for junk food.)

So how can physicians more successfully influence their patients?

Their ability to persuade their patients to try something new may come not from their medical authority but from their perceived similarities with the patients. For instance, paediatricians are often more influential in giving advice to parents when they supplement medical information with anecdotes about their experiences with their own children. Their influence comes as much from being parents as from being doctors.

A particularly well-known example in the medical community is vaccination. For new parents trying to determine the credibility and safety of vaccines, the opinions of other parents are often seen as more relevant than the opinions of expert epidemiologists. It is not surprising that physicians’ advice about vaccination is often more influential when they share stories about vaccinating their own children.

The same principle powers the success of the online patient community Patients Like Me. People with rare illnesses are receptive to advice coming from others who have the same condition. For patients considering the use of a new medical device or weighing whether to join a randomized controlled trial, advice from peers who have faced similar challenges is often viewed as more credible than advice from medical professionals.

Excerpted with permission from Change: How To Make Big Things Happen by Damon Centola, published by John Murray/ Hachette India