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The panel shows thumbnail images of the same woman, before and after weight loss. When the photo of the overweight woman was shown, participants perceived the same set of meals to be less healthy.

A blogger’s weight affects her or his credibility with readers seeking food advice, according to a Cornell study published online and in a forthcoming print issue of the journal Health Communication.

The findings are important because the Internet has fast become a leading source of health information, with more than half of smartphone users reporting they use their device to look up health-related information via health and nutrition websites and food blogs.

But two experiments by Cornell researchers reveal that when a blogger is overweight, as shown in the blogger’s photo, readers are far more skeptical of the information that blogger provides when compared with a thin blogger’s recommendations, even when the content is exactly the same.

The findings have important implications.

“When we search for health information online, there are a lot of related cues that can bias our perceptions in ways that we may not be consciously aware of,” said Jonathon Schuldt, assistant professor of communication and lead author of the study. Awareness of these biases could help us better navigate health information online, he said, and avoid being swayed by nutritional information simply because it is posted by someone who is thin rather than heavy.

But the study also suggests that “weight bias and prejudice – which are so rampant in our society – can spill over and affect not only the inferences we make about people, but also objects that are associated with them,” Schuldt said.

In one experiment, 230 subjects were randomly assigned to one of two groups. They were all shown photos that one might find on social media websites of the same 10 meals – including black bean and cheese quesadillas, chopped salad with croutons, sliced beef with vegetables and so on. With each photo was also a thumbnail photo depicting the supposed author of the blog post. Participants were then asked to judge how healthy the meal was overall on a scale of one to seven. The only thing that differed between the two groups was the thumbnail photo of the blogger, which was a real picture of the same person before and after weight loss.

The researchers found that when the photo of the overweight woman accompanied the meal, “our participants perceived those meals to be less healthy” than the same meal presented with a photo of a thin blogger, Schuldt said. “People appear to assume that if a heavier person is recommending food, it is probably richer and less healthy,” he said.

In a second experiment, the researchers also included calorie and fat content information next to the image of the food and above the thumbnail of the blogger. “What we found is that even when we provided nutrient information that is much more relevant to the food’s health quality, people are still strongly influenced by the body weight of the recommender,” Schuldt said.

The researchers even went so far as to vary the fat and calorie content, so that some subjects saw a healthy nutritional label and others saw a label with approximately double the calorie content and triple the fat. They found that this increase in fat and calories influenced impressions of the meals’ healthfulness to a similar extent as the heavy vs. thin blogger, all else being equal.

“When we dramatically increased the fat and calorie content, it had just as much impact as when we said the food was posted by a heavy person,” Schuldt said.

Co-authors include Jamie Guillory Ph.D. ‘12, now a researcher at RTI International, and Geri Gay, the Kenneth J. Bissett Professor of Communication at Cornell and a Stephen H. Weiss Presidential Fellow.