Aetna Inc.'s $5.7 billion purchase of Coventry Health Care Inc. will take the insurer from about the bottom to the top of leverage among its peers as it seeks to cut $400 million of costs.

Aetna's push to compete with WellPoint Inc. and Cigna Corp. as the U.S. government increases medical coverage will bring its debt to about 40 percent of capital from about 31 percent, according to Fitch Ratings. That would be the highest among the six firms in the Standard & Poor's 500 Managed Health Care Sub Industry index.

While Chief Executive Officer Mark Bertolini has pledged to trim leverage, the purchase's profitability depends on cuts to management and technology spending that may be difficult to achieve, according to CreditSights Inc. The three major credit- ratings firms lowered their outlooks for the Hartford, Connecticut-based insurer after it announced the deal Aug. 20 and said it would take on $2.5 billion of debt to finance it.