Why do you gain pounds in a day when you are on a diet and doing everything right?

i heard that some people before getting on to a diet stress their bodies by thinking that they wont be able to have the food they like, will stay hungry, and starve. by doing so they cause their brain to send false alarm signals to the rest of the body that it will starve, and as a result what will happen inside is the following: the body will automatically save calories to use it up as energy, and save the water fat, and in the end your still eating, even though healthily and still not loose weight

try not to stress out when begging a diet.