I started taking Magnesium Citrate recently and have also noticed an increase in appetite and metabolism/digestion. I have also noticed more energy, mental clarity, and calmer nerves than before; along with a loss of water bloating in my face in the morning and slimmer abdominal region.
I am a physically and mentally active 22yr old male, and my body seems to be demanding more fuel to keep it going. I think this is a natural response, as I was on a somewhat calorie-restricted diet before. I've found that what IS important is WHAT you eat when the hunger kicks in.
I have been eating only natural foods; whole grains (brown rice, oats, quinoa), vegetables, fish (salmon, sardines), eggs, fruits, nuts, seeds, natural oils (olive, coconut); and it feels amazing! I would highly recommend a natural, wholesome diet to fuel your body's increasing demands rather than fast food and common snack food.
Avoid foods with added sugar, soft drinks, fried foods, potato chips, etc. A lot of these actually deplete your body of nutrients, while your body wants MORE nutrients. Your body will thank you for the natural food and reward you with clean, bursting energy! Hope this helps :)