When Apple put the original iPad under the knife, it yielded a fetchingly slimmer iPad 2. IHS iSuppli shows how they did it.

"Thinner is better" is an Apple mantra. And the popularity of the MacBook Air, iPhone, and iPod proves that consumers agree. The iPad is no exception.

iPad 1, iPad 2 thickness comparison.

By shaving off a sizable 34 percent of the original iPad's body fat--to 8.8 millimeters from 13.4 millimeters--Apple got the weight down to 600 grams, down 15 percent from 700 grams for the iPad 1.

How did it do it The biggest reduction in thickness came in the iPad 2's battery subsystem, wrote Kevin Keller, a teardown analyst at IHS iSuppli, in a research note today. This part of the iPad 2 is 2.5 millimeters thick, a 59 percent reduction from the 6.1 millimeters of the original iPad, according to Keller.

"The iPad 2 battery design represents a major shift from the iPad 1," Keller said. "Apple moved from two thicker cells to three thinner ones, flattening out the entire battery structure. The new design also allowed Apple to eliminate an injection-molded plastic support frame from the battery subsystem, further cutting down its thickness."

This refinement yielded a 10 to 15 percent increase in the iPad 2's power density, a measure of battery life relative to the mass of the battery, according to Keller.

Other weight-loss factors include the elimination of a stamped sheet metal frame from the display--slashing the size of the display 17 percent from the iPad 1--and new glass technology that reduces thickness but maintains durability.

"Apple has particularly focused on thickness as a point of differentiation for the iPad 2. Other new tablets coming to market, all of which are about as thick as the iPad 1, now look fat in comparison to the iPad 2. This is likely to cause a scramble as competitors rush to slim down to match Apple," Keller wrote.