Is it healthy to lose 10 pounds in a week?

When it comes to weight loss and safety, the difference between safe and unsafe doesn't have to do with how much you lose but how you lose it. Losing 1-2 pounds per week is often cited as a safe amount, but little safety data exists to support that number. What makes 3-4 pounds unsafe? Only the way in which you lose it.

If you drink nothing but lemon juice and maple syrup with a dash of cayenne pepper for a week and lose 10 pounds, I would consider that unsafe weight loss. On the other hand, if you complete three intense,metabolic resistance-training sessions, another three interval-training sessions, and you are diligent about eating a low-calorie, carbohydrate diet and lose 10 pounds in one week; I wouldn't say that was unsafe. I would say you worked hard and lost the weight the right way. I should note that 11 pounds is the most weight I have ever had a client lose in one week (not counting athletes that were cutting weight). This client worked extremely hard to lose that weight, and he was relatively fit to begin with.

The question of losing 10 or 20 pounds in one week has become very popular, thanks to TV shows like The Biggest Loser. When losing "biggest loser" type numbers, there are three major factors that come into play: weight to lose, time, and experience/fitness level.