When dieting the amount of calories is reduced, the human body tends to consume the calories accumulated in the muscles since the ones brought by the food are not enough. The result is a loss of muscular mass and of water, but not of fat mass. Therefore the percentage of body fat in respect of the total mass will increase. When this happens, the doctor will correct the habits of the patient so that the loss of mass is in the same proportion for all kinds of tissues. On top of the correct diet, he will surely recommend the patient to increase their physical exercise to stimulate the muscles and also to control the level of hydration. A periodical measurement of the body fat will help to minimise this effect.

The human body takes some time to get used to a new diet, so it is advisable to take a 2-3 week control period before confirming if there is a loss of muscular mass and/or hydration, as well as whether the fat mass decreases or not, before making any changes in the programmed diet.