You said "thinner". You can be 'thin' and still have all kinds of body fat. Losing 4 - 5 lbs a week will make you thin - it wont make you lean. It most certainly will not make you 'healthy'. Losing muscle mass makes you lighter and proportionally fatter. It lowers your metabolism. Being 'thin' shouldn't be a goal - not at the expense of being healthy.

Nat