The watchdog group Public Citizen on Tuesday released a research brief about the hundreds of millions of dollars Medicare Advantage companies have spent on lobbying ahead of a U.S. Senate confirmation hearing for Dr. Mehmet Oz.

Oz, a heart surgeon and former television host, is President Donald Trump’s nominee to run the Centers for Medicare and Medicaid (CMS)—an agency in the U.S. Department of Health and Human Services, which is led by conspiracy theorist Robert F. Kennedy Jr.

Health experts and others have sounded the alarm about Oz since Trump announceded his nomination in November, with many opponents highlighting the doctor’s investments in companies with direct CMS interests and his push to expand Medicare Advantage when he unsuccessfully ran as a Republican to represent Pennsylvania in the U.S. Senate in 2022.

Medicare Advantage is a type of CMS-approved health insurance plan from a private company that seniors can choose for medical coverage instead of government-administered Medicare. Critics often call it a “profit-seeking healthcare scam.”

Public Citizen’s brief points out that last year, “more than half of all seniors eligible for Medicare were enrolled” in these private plans that “cost taxpayers hundreds of billions of dollars and deliver inferior care compared to traditional Medicare.”

“Since their inception in 2003, Medicare Advantage plans are estimated to have cost taxpayers more than $600 billion in overpayments,” the document notes. “These overpayments are expected to grow to $1 trillion over the next decade.”

“Just seven companies account for 84% of all Medicare Advantage enrollment,” the brief continues. “While lobbying disclosures do not reveal how much is spent on a single issue, disclosures reveal that these seven companies spent more than $330 million combined lobbying on all issues over the last five years, according to data from OpenSecrets.”

Those companies are UnitedHealthcare, Humana, Blue Cross Blue Shield, CVS Health, Kaiser, Centene, and Cigna.

Public Citizen found that in 2024, they collectively had 328 lobbyists targeting the federal government, with nearly 70% of them specifically working on Medicare Advantage. Blue Cross had the most lobbyists focused on such plans (99), followed by Humana (33) and UnitedHealth Group (27).

“If Oz is confirmed as the CMS administrator, attacks on traditional Medicare are likely to move into overdrive,” Eagan Kemp, a healthcare policy advocate at Public Citizen, warned in a Tuesday statement. “We should strengthen Medicare by improving it and expanding access to it, not weaken it through further privatization.”

The Senate Committee on Finance is set to consider Oz on Friday morning. Since Trump returned to the White House in January, the GOP-controlled chamber hasn’t blocked any of his nominees.