Ignorance may be bliss, but if you have a cell phone, it may no longer be an excuse to indulge in unhealthy eating, at least not at chain restaurants.

Last week, Diet.com launched Nutrition on the Go, a text-messaging service that lets you check out the calories, carbs and fat of common items at 1,700 places. Send a text message to 34381 with the name of the restaurant and the item you plan to order. The results can be shocking: For example, tuna sandwich on honey wheat bread at Panera has 720 calories, 43 grams of fat and 50 grams of carbs. To test the service online, visit http://diet.com/mobile.