reducing a double chin. When the human body is short of salt, it means the body really is short of water. The salivary glands sense the salt shortage and are obliged to produce more saliva to lubricate the act of chewing and swallowing and also to supply the stomach with water that it needs for breaking down foods. Circulation to salivary glands increases, and the blood vessels become "leaky" in order to supply the glands with more water to manufacture saliva. This "leakiness" spills to area beyond the glands themselves, causing increased bulk under the skin of the chin, the cheeks, and into the neck.
Now you know what is missing in your lifestyle which cause double-chin : water deficit. So increase water gradually to suit your weight.