Is it normal for low calorie diet resulting rapid weight loss?

Not safe: Rapid weight loss has the following risks - gallstones, which occur in 12% to 25% of people losing large amounts of weight over several months. Dehydration, which can be avoided by drinking plenty of fluids. Malnutrition, usually from not eating enough protein for weeks at a time. Electrolyte imbalances, which rarely can be life threatening.

Yes it is normal but: You got to realize that there's a set-point for your weight in your brain that when weight is lost rapidly, your brain will try to get your weight back to the start weight after a few weeks. So it's is critical to follow the low calorie diet (800-1100 kcal) with a proper maintenance diet to ensure your weight loss is rather long term and not short term.