Been there, done that and have a t-shirt for it. It is easier to maintain weight that is loss in small amounts because it is more likely to be real fat loss. Most, if not all fad diets usually results in excess water loss first. Changing to healthy eating habits can result in initial large amounts of weight loss the first week or so, but it should slow down. The change may again result in ridding the body of excess retained water. Proper eating, diet and exercise should result in small amounts of weight loss. The target should be to eat a healthy diet and burn more calories than you take in. Once your at your goal increase calories intake, continue a healthy diet to include controlled intake of bad food and continue a healthy exercise routine to maintain the healthy weight. The faster the weight comes off, the easier it will be to pile back on. Slow and steady wins the race.
Firstly, people on the biggest loser are usually very overweight. They just have more lbs of fat to lose then most people, so its easier to take it off faster.Also, it is safe and possible to lose more then 1-2 lbs a week, but you do need to do it through exercise not just diet. If you expect to lose weight permanently, you need to be not starving yourself. You d need to be doing a very long/hard workout almost ever day to lose more then 1-2 and it can be difficult to keep on that kind of program, and many people just don t have that kind of time/energy.