A medical research concluded that rather than the reason of lack of exercise, a poor diet is the major cause of the Obesity. While the authors’ research shows that only about half of lay people claimed the reason of poor diet as a cause of obesity. Individuals succeeded to avoid overweight who agrees with the concept, on the other hand, it found a serious gain of weight in people who did not correctly believe the importance of a poor diet. The various food and beverage companies, in their campaigns of marketing, CSR, and public relations,exaggerate the lack of exercise as the primary reason of obesity, which called by the author as “leanwashing”.