After two to three days the body starts using the fat in the fat cells. Since the body wants to preserve its reserves, it first throttles its energy consumption. It adjusts metabolism, changes hormones and loses muscle mass when losing weight.
But even if the reserves are exhausted, the fat cells will not disappear completely. They just empty and shrink. If there is enough food again, they fill up in a flash to be prepared for times of need – the well-known yo-yo effect.
When the body metabolizes fat from fat cells, it produces molecules called ketones (also known as ketone bodies). Most cells in the body are able to turn ketones into energy. The body is in the ketogenic phase or in the so-called ketosis. This condition can be controlled very well in the first weeks via urine test tyres. This is particularly important for ketogenic (carbohydrate-limited) diets. These diets can, for example, have a positive effect on the course of some forms of epilepsy.
Ketones also reduce the pH. Acidification is the result. Especially with the popular Atkins diet, the risk of acidification is high. In the worst case, there can be a threatening ketoacidosis, an extreme acidification with ketone bodies. The body desperately tries to excrete the ketones via the kidney and retains uric acid. The result can be a gout attack.
In addition to balance, care should also be taken to the intake of basic minerals during a diet and especially during a fasting cure!
For people on diet, from the point of view of urinalysis, the examination of the ketone bodies (whether the ketogenic phase is present) and the pH value are particularly interesting. Both values should be monitored for a longer period of time.