Ads take up just 9% of the space on a web page, but are accountable for 54% of the load time, the study found.
This results from the data tracking and cookies that come with ads.
The theory is that frustration at this slow load time is causing people to turn on ad blockers.
"We believe that the misuse and lack of control over advertising technologies is a major, if not the major, contributing factor to the increasing use and adoption of Ad blocking solutions," the report said.
"It is our hypothesis that advertising technologies are negatively impacting publisher websites," it added.
Here are the key findings of the study for US publishers:
Secret Media looked at the webpages of 25 top US media companies. The load time, bandwidth, and URL requests of pages with ad blockers switched on were compared with the results of the same pages with ad blockers switched off.
The data is anonymized, but for all publishers, ads significantly increased load times. The top 25 media companies included CBS, Vice, The Huffington Post, NBC, and Business Insider.
The effect of ads on load time is clear:
The study found similar results in Germany and France, where the adoption of ad blockers is also very high.