Drinking a glass of water up to 30 minutes before a meal will also naturally aid portion control. Filling up on water will make you feel less hungry. Being well hydrated also helps you distinguish between hunger and thirst.
One study in middle-aged and older adults observed that drinking 17 ounces (500 ml) of water before each meal resulted in a 44% greater decline in weight over 12 weeks, most likely due to reduced food intake (Source). Similarly, when overweight and obese older adults drank 17 ounces (500 ml) of water 30 minutes before a meal, they consumed 13% fewer calories without trying to make any changes (Source).