This is called purging. Purging is a situation when a person gets rid of ingested food voluntarily. This is in contrast to vomiting which is often involuntary. Purging is usually manifested by people with eating disorders such as buliumia nervosa and body dysmorphic syndromes.
Starvation is the lack of nutrients due to reduced intake of food and constipation is reduced frequency of defecation associated with difficulty in defecation.