Sugar-free drinks have become popular because of their high calorie content, which can easily lead to obesity. After a period of investigation, Professor Li believes that just because sugar-free drinks are low in calories doesn't mean they won't lead to weight gain. Because sugar-free drinks may lead to a high preference for sweets, this means eating more sugary foods. Moreover, sugar-free drinks have little nutrition, and drinking too much limits the intake of other healthy drinks, such as tea and fruit juices.
Many fat people report to the doctor that they often drink sugar-free drinks can best support Professor Li's point of view.