Malnutrition refers to deficiencies, excesses, or imbalances in a person''s intake of energy and/or nutrients. Child malnutrition, in all its forms, includes undernutrition, which includes wasting (low weight-for-height), stunting (low height-for-age) and underweight (low weight-for-age), micronutrient-related malnutrition (a lack of important vitamins and minerals) or micronutrient excess, overweight, obesity, and resulting diet-related non-communicable diseases. Malnutrition is one of the most important factors for improper physical and mental development of children. One in every five children in the developing world is malnourished, and poor nutrition is associated with half of all child deaths worldwide. The problem of low or excessive body weight concerns countries with different levels of socio-economic development. This is a medical, social, and economic issue. Every country in the world is affected by one or more forms of malnutrition. Combating malnutrition in all its forms is one of the greatest global health challenges. Infants, children and adolescents are at particular risk of malnutrition. In children, malnutrition has particularly significant health consequences during both early development and adulthood. Malnutrition endangers children''s survival, health, growth and development, slows national progress towards the developmental goals and thus diminishes the strength and capacity of nation. Malnutrition in terms of undernutrition is substantially higher in rural than in urban areas and children from indigenous populations often have the poorest nutritional status. The developmental, economic, social, and medical impacts of the global burden of malnutrition are serious and lasting for all involved including individuals and their families, communities and countries. Poor nutrition during the early years of life can also have severe consequences for subsequent skeletal and immunological development. Studies have demonstrated that undernutrition is not caused by food insecurity alone. Other factors range from the length of the breastfeeding period and the availability of milk oligosaccharides, pathogen exposure, and enteric dysfunction marked by villus atrophy and loss of gut barrier function. Differences in the succession of microbial establishment and maturity might contribute to family discordances in nutritional status. Childhood obesity is one of the most serious public health challenges of the 21st century. The problem is global and is steadily affecting many low- and middle-income countries, particularly in urban settings. Its prevalence has increased at an alarming rate. Globally, in 2016, the number of overweight children under the age of five is estimated to be over 41 million. Almost half of all overweight children under 5 lived in Asia. Overweight and obesity have been linked to adverse psychological and physical outcomes during childhood and continuing into adolescence and adulthood. The association between overweight and obesity with psychosocial problems (anxiety, depression and negative self-image), health problems (diabetes and cardiovascular events) and impaired social, educational and economic productivity has been well documented. Moreover, the negative impact of being underweight, overweight, or obese on the health and development of children and adolescents can also extend into adulthood, increasing the risk of chronic non-communicable diseases and disability. Overweight and obesity, as well as their related diseases, are largely preventable. Therefore prevention of childhood obesity is a high priority. The mechanism of development of obesity is not fully understood and it is believed to be a disorder with multiple causes. Environmental factors, lifestyle preferences, and cultural environment play pivotal roles in the rising prevalence of obesity worldwide. In general, overweight and obesity are assumed to be the result of an increase in caloric and fat intake. On the other hand, there are supporting evidence that excessive sugar intake by soft drink, increased portion size, and steady decline in physical activity have been playing major roles in the rising rates of obesity all around the world. Nutritional assessmentis the interpretation of anthropometric, biochemical, clinical and dietary data to determine whether a person or groups of people are well nourished or malnourished (over-nourished or under-nourished). Research can be aimed at identifying the various social, cultural, political, and economic factors of nutrition in order to fully understand the underlying causes of malnutrition. The social determinants of malnutrition can be explored through both qualitative and quantitative research methods. Furthermore, exploring the issues of food security, dietary diversity, and infant-feeding practices can provide a comprehensive understanding of a population''s nutritional status.