Starving a Hatchi will not make it lighter, but it will have a negative effect on its happiness. Continuing to neglect this stat will cause your Hatchi to die.
Hygiene is one of the two important Hatchi stats, with the other being Hunger. An empty Hygiene meter will cause your Hatchi to smell, and if the Hygiene stat is constantly neglected, your Hatchi will die. Hatchi poop also effects Hygiene, so if you see any, clean your Hatchi.
When this stat is low your Hatchi is in need of some intellectual stimulation. It will gradually decrease over time. Hatchis can learn from reading books and playing Hatchi Matchi, Roshambo, and Hatchi Squares. It also effects how your Hatchi looks when it becomes a child; a smart but lazy Hatchi will take on a more humanoid form rather than the appearance of a spiky blob.
When this stat is low on your Hatchi, it needs some physical stimulation. As with SMARTS, it will decrease gradually over time Hatchis become more active by participating in the games Hatchi Catchi, It's Raining Meds, and Whack-A-Hatchi. Physical activity, like intelligence, can effect a Hatchi's evolution from baby to child; an athletic yet uneducated Hatchi will become a spike ball instead of a humanoid.
When your Hatchi is awake, its ENERGY will go down and when it is asleep, its ENERGY will go up. Hatchi evolution is unaffected by its energy level, and a Hatchi will not become sick if its energy meter is neglected for long periods of time. However, if one wants to earn lots of coins, it is a good idea to maximize a Hatchi's energy meter so they can play games many times.
Happiness is an important stat in Hatchi. It is one of the stats that effects evolution, but only at the teen stage. Example: Lesser Demon (the overweight teenage evolution of the Active child) evolves into Devil with high Happiness instead of Demon. Also, if you inject your Hatchi with medicine, its happiness will decrease. However, repeatedly injecting your Hatchi will not kill it. This is helpful when you are trying to get your teen to evolve into a different Hatchi.