A system includes the Internet network; a digital weighing scale device, coupled to the Internet network, for weighing a current user body to detect a current weight value and outputting diet information; and a server computer, coupled to the Internet network, for providing the diet information corresponding to the current weight value to the digital weighing scale device. The digital weighing scale device has a liquid crystal display (LCD) and a printer. The system further includes a client computer. The server computer has a World-Wide Web (Web) site, which is made up of at least one Web page, A user at the digital weighing scale device can input user-input information into the server computer, wherein the user-input information includes a user identity, a user sex, a user height value, user waist and hip circumference values, a target time period and a target weight value. Alternatively, the user at the client computer can input the user-input information into the Web page.