There is a double burden of Malnutrition and Overnutrition in the world. Malnutrition includes hunger, Protein-Energy Malnutrition (PEM) and a variety of Micronutrient Deficiencies (MNDs), severe It is harmful to children's development, maternal health and the quality of life of the elderly. At the same time, excessive consumption of high-calorie and low-nutrition ultra-processed foods (UPFs) leads to chronic non-communicable diseases such as obesity, Type 2 Diabetes (T2D), cardiovascular diseases and some cancers (Non-Communicable Diseases, NCDs) are widely prevalent. In many developing countries, there is even a "double burden of malnutrition" (DBM) of malnutrition and obesity. Based on the conceptual framework of "Food as Medicine" (FAM), this paper systematically explores the core role of eating in the prevention of these two types of nutrition-related problems through comprehensive literature review. In response to malnutrition, the article analyzes how to intervene through fortified food and nutrition-intensive natural food. For overnutrition and related chronic diseases, Mediterranean Diet, Dietary Approaches to Stop Hypertension (DASH) were evaluated. The effectiveness of evidence-based diet models such as Plant-Based Diets (PBD). In addition, the paper clarifies the auxiliary position and use risks of Dietary Supplements in filling specific nutritional gaps, and discusses Portion Control and Mindful Eating and key behavioral strategies such as Cultural Adaptation. The core conclusion emphasizes that food is the fundamental "medicine" to meet global nutritional challenges. Establishing a balanced diet based on diversified Whole Foods is the core of health, and supplements should only serve as an aid to clear shortages. To promote "food is medicine" in the future, it is necessary to develop into Personalized Nutrition, deeply integrate nutrition intervention into the health care system, and focus on the accessibility and affordability of healthy food to ensure that all people, especially vulnerable groups, can get nutritious food to achieve the ultimate goal of improving the outcome of global health.