What the health ministry notification did was allow the use of synthetic sugar substitutes like aspartame and acesulfame under the Prevention of Food Adulteration Act. Aspartame and acesulfame are the critical chemicals in low-calorie soft drinks. Pepsi, which had waited for years for this permission and was in full readiness to launch Diet Pepsi, was all over television within hours of getting the clearance; the TV ads promised just one calorie in its 330-ml can.