Why does microwave oven heats up a food item containing water molecules most efficiently?

A microwave oven, heats food up by producing waves having frequency equal to the resonating frequency of water molecules. As all food items have water, the water molecules absorb energy from these waves and start vibrating. This vibration produces heat and the food gets heated. Thus, food items having excess water will be heated most efficiently as there would be more water molecules to vibrate and heat the food.