VANCOUVER -- New research out of a B.C. university found that people with obesity were more responsive to food marketing, but that responsiveness dropped when they lost a significant amount of weight.

The study, conducted at the University of British Columbia, suggests the findings are important because researchers assumed for years that food marketing is responsible to high rates of obesity in developed countries.

Dr. Yann Cornil, lead researcher on the study, told CTV News Vancouver there doesn't appear to be any evidence of that.

"People with obesity tend to be more responsive to marketing tricks, to marketing techniques and tend to underestimate calories more when a product is marketed as healthy," he said. "They tend to upsize their portions."

Researchers followed patients with severe obesity before and after they had weight-loss surgeries, people with obesity who did not undergo weight-loss surgery and people who were not obese.

The research team says it's not clear whether people become less responsive to marketing because of psychological changes following the surgery or because of a desire to change their lifestyle and habits.

"The results clearly suggest a bidirectional influence between people’s weight status, psychology and responsiveness to the environment — including marketing," Dr. Cornil said.

"So, it’s a complex relationship."