What are causes of undernutrition?

The causes are many.

the person who is under nourished may not have the capacity to digest and absorb the necessary ingredients from his diet. by saying capacity i mean that his vitality may have been very low when he was born or has deteriorated with the modern lifestyles. it is quite possible that what he thinks as good nutritional base was probably grown with chemical fertilizers that hinder absorption. the modern day lifestyle of overeating sedentary lifestyle. the wrong kind of foods, in between munches and crunches.

heavy constipation can also hinder absorption of necessary nutrients by the body.

a complete overhaul of lifestyle eating habits, exercise, a positive bent of mind and a clear understanding of what is good as food, lifestyle etc .

laziness can also contribute to undernourishment...

the more you are active the body demands food..that is real hunger, and when you are really hungry the body will be able to get the last aota of nutrient that is due to the body from whatever you eat provided they are positive.

smoking , alcohol and drugs etc...with other habits bad can also be causes.

there are cases where it is a case of poverty...here again the lifestyle...living very near to garbage , poor sanitation eating old food, or just tea bunj and biscuits, are causes. smoking and alcohol is also common in poverty stricken cases..