Amy is right! Shows like Biggest Loser and Overhaul do have a lot to answer for. The people in these shows are:
a) very obese - most of them morbidly, so therefore have a lot of weight to lose, and will lose more quite quickly than Mr or Mrs Joe average that only needs to lose say, 25kg or less.
B) In a situation where they quite literally concentrate on losing weight 24 hours a day. There are no outside distractions like Mr and Mrs Joe Average deal with every day - finances, running the house, running the family, work etc.
Unfortunately, people watching these shows do not take these factors into consideration, and then think that losing 8 - 10 kilos in the first week and then 4-6 kilos a week thereafter is normal.
Reach for the moon, at least you'll land among the stars.