The benefit is quicker weight loss. But a downfall occurs only if you go too low (more than 20-40% of your calorie maintenance) for too long (2-6 weeks).

The ranges are based on how overweight you may be. In other words, if you are slightly overweight (~10-20 pounds), you would stay at the lower end of the ranges. The more over your healthy weight you are, the larger the deficit can be. But as you close in on your goal, you should begin to shrink deficit in order to help maintain results.

Additionally, deficits that are too large can also lead to loss of muscle as opposed to the use of smaller differences between calories consumed and burned. Always keep in mind that slow weight loss (approximately 1 pound per week) is the best method for long-term results.