Time Inc. says it plans to shake up its publication roster to focus on profitable brands.

The publishing arm of

Time Warner

(TWX)

says it is putting 18 magazines up for sale, including Popular Science, Field & Stream and Parenting.

The niche magazines are "no longer fit with our strategy for Time. Inc's future," Time Inc. CEO Ann Moore said in an internal memo obtained by

TheStreet.com

.

"Time Inc. is focusing its energy, resources and investment on our largest and most profitable brands," Moore said in the memo Tuesday.

Titles like Sports Illustrated, Fortune, Money, Discover, Time, Golf and This Old House will remain as part of the core focus for the company.

Time Warner shares have been largely flat for the past three years. This has attracted activist investors like Carl Icahn, who pressured the company into a huge stock buyback.

"This was not an easy decision," Moore said in the memo. "These are all vibrant and valuable brands."

Time Warner shares closed up 14 cents at $17.04 Tuesday.