I've been in a diet for almost three weeks by not eating breakfast and lunch but are there supposed to have any side effects? I managed to lose 3.4 kg from my usual weight of 49 kg. But why are my nails getting thin and chips off easily? Is it due to my diet or because of some weird nail infection?
But my nails don't have any thing that resembles infection, or so I think because it looks pretty much the same as it usually does except it's thinner andcracks easily. Please help!

You are not eating properly which is why your nails are doing that. One meal a day is not a safe way to lose weight.
The key to losing weight is to eat balanced meals and get exercise.

Why are you dieting? You're not overweight! Stop starving yourself, it's dangerous. You need to tell your parents what you're doing, so they can help you. Feeling the need to lose weight when you don't need to can be a mental illness, and a very scary one at that.

I know you're not overweight because you said what you're weight and height are in your other question.