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Why would anyone make a conscious effort to match body text with AdSense ads unless it was to trick users and cheat advertisers?
The thread Jenstar pointed out can help you determine the font in your Google ads so that you can match your content font to the AdSense font. However, we ask that you do not alter the AdSense ad code beyond the options available on the Ad Code Layout section of your account pages as this is prohibited by the ToS.
Hope that helps, and as always, thanks for asking first.