Up until now, the FDA has not set levels for products to be low carb or reduced carb. They have promised that they will do so in the next few months.
The issue is that some companies knock only a single carb off of a product - and vastly increase its price and calorie count - and still try to call it "reduced carb". Other companies label their products as "low carb" even at counts of 20g per serving or higher.
FDA Deputy Commissioner Lester Crawford has pledged to set down rules for companies to follow, so that consumers have a sense that a product actually delivers on what it offers.
Until the FDA makes its decision, it is warning all companies that the terms "low carb" and "reduced carb" are NOT allowed on any product labels.
For reduced carb, the FDA is looking into setting that the new product must have at least 1/4 less carbs than the original product formulation.
For low carb rating, the Grocery Manufacturers of America wants the limit set at 9g/serving. The CSPI, a consumer group, would rather have the limit set down at 6g/serving.
Lisa Shea's Library of Low Carb Books