Malnutrition is a condition in which a body does not receive the proper or sufficient amount of nutrients. If not treated immediately, it can lead to death.
Kira Nerys was brought up believing her mother, Kira Meru, died of malnutrition at the Singha refugee camp on Bajor, when in reality, she lived with Gul Dukat on Terok Nor, a Cardassian space station in 2346. (DS9: "Second Skin", "Wrongs Darker Than Death or Night")
In 2370, Lieutenant Commander Data's memory was wiped and he was damaged after he tried to recover a downed Federation probe from the planet Barkon IV. Talur, a native of the planet, surmised that Data was an iceman suffering from malnutrition after he wandered into the Barkonian's village from the Vellorian Mountains. (TNG: "Thine Own Self")
In 2376, Lieutenant Commander Tuvok told the criminal Dala a false story about imprisonment by a species she had conned from, the Telsians and said that the inmates at their prisons often died of malnutrition. (VOY: "Live Fast and Prosper")