?As known, our diet affects our health. Also we all knowthat eating a healthy diet prevent all disease and healthproblems. (Harvard T.H. Chan School of Public Health) A healthy diet can also help you maintain a healthy weight andlead to better overall performance of the mind. Healthy eatingimproves our immune system and mental health. So it givesenergy and prevents all disease. ?A healthy diet, according to the Harvard Healthy EatingPyramid, means eating all types of healthy foods andnutrients. From the wider part of the pyramid to the narrowtop people have to eat whole grain food and plaint oils, vegetables, fruits, nuts and legumes, fish and poultry and eggs, dairy or calsium supplement, red meat and butter and refinedcarbohydrates. It shows us that people have to eat less at thetop group which includes red meat, butter and carbohydrate. Eating a healthy diet in every meal improves our immunesystem. With a strong immune system, all diseases can be prevented.?”Healthy diets and physical activity are key to goodnutrition and necessary for a long and healthy life.” (WHO Technical Report Series, No. 916) Recently researchs Show that healthy foods and nutrient intake and also physicalactivity can prevent obesity, diabetes, cardiovascular disease, several forms of cancer, osteoporosis and dental disease.Obesity is the biggest health problem of our century.Unhealthy foods and non-nutritious foods and processed foodscause overweight and obesity.?While overweight and obesity cause of chronic diseasesuch as coronary heart disease, diabetes, stroke and also death. Eating healthy foods and nutrient dense foods and balancingenergy intake with the necessary physical activity to maintaina healthy weight is essential at all stages of life. ?Unhealthy diet can lead to obesity, which is a risk factorfor certain cancers, heart disease, stroke and diabetes. But thegood news is that people can prevent or reduce almost alldiseases with eating a healthy diet.