Coke and Pepsi are reporting 2014 earnings this week. In both cases, we are likely to see two versions of the same basic story—changing tastes at home, coupled with a strong dollar and weak economy abroad, are taking some of the pop out of profits.

But luring back calorie-conscious customers is not as simple are taking out the sugar. Shareholders and investors don’t like to see companies stray too far from their core product, which in the case of Coke and Pepsi, remains regular old sugar soda.

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