explain the importance of good nutrition to health.?

i need some help if you could please explain the importance of good nutrition to health please? GOOD NUTRITION means the RIGHT FOOD to eat….Good nutrition is very vital for good health,for example,if we eat less vegetables,fruits and more of junk foods,sweets,fatty foods…we tend to develop diseases that are related on what we eat,like TOO MUCH SWEETS=DIABETES MELLITUS, TOO MUCH OILY FOODS=GALL STONES, TOO MUCH SALTY FOODS=KIDNEY RELATED DISEASES..