Patrick Johnston, president of the California Association of Health Plans, said insurers are supporting the implementation of health changes, but the report underscores a concern about cost increases.

"All these expansions add to the already increasing cost of care â¿¿ costs that have outpaced inflation as obesity, chronic conditions and many other factors have driven up medical expenditures," Johnston said in a statement.

The study also showed that younger adults will experience higher rate increases while older adults could see decreases. Exchange officials said increases could be offset by federal subsidies because younger people tend to earn less and people under 30 can select a catastrophic plan for less money.

Adults under 26 can also remain covered under their parent's health plans, which was one of the provisions that has already gone into effect.

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