Final answer:
The food guide before the 90's is outdated because it is based on outdated nutritional science and does not reflect our current understanding of nutrition and health. The 1990s fat-free trend led to the popularity of fat-free foods, which were often unhealthy and could lead to weight gain. The most recent food guide called 'My Plate' reflects the latest research on nutrition.
Step-by-step explanation:
The food guide before the 90's is outdated because it is based on outdated nutritional science and does not reflect our current understanding of nutrition and health. For example, the 1970s 'Four Food Groups' and the 1992 'Food Guide Pyramid' were criticized for putting too much emphasis on grains and not enough emphasis on fruits and vegetables.
In addition, the 1990s fat-free trend led to the popularity of fat-free foods, which were often highly processed and loaded with added sugars to compensate for the lack of flavor. This trend was later found to be unhealthy and could lead to weight gain instead of weight loss.
Today, the most recent food guide called 'My Plate,' emphasizes a more balanced approach to eating, with equal portions of fruits, vegetables, grains, protein, and dairy. It also encourages consuming less processed foods and added sugars. This new food guide reflects the latest research on nutrition and the effects of diet on health.