We explore the potential causes, treatments, and, Medical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. Our team thoroughly researches and evaluates the recommendations we make on our site. These conditions are not permanent, and therefore you should not worry about them too much. For more information, please see our As we have gathered, one of the most common causes of a foul smelling urine is ketosis. However, if the unusual smell persists, it is worth seeing a doctor to determine the underlying cause. This can be an indication that the body is not absorbing all of the nutrients from the foods you eat. Fat cells release their stored energy in the form of triglycerides, which are then used by the body for fuel. Before weighing intermittent fasting side effects, it's important to know that there are several forms of intermittent fasting, and the evidence of their long-term effectiveness and safety is not yet known. Effect of fasting on the urinary excretion of water-soluble vitamins in "Fasting activates an evolutionary program in which our body diverts nutrients normally used for growth and reproduction toward mechanisms for repair and survival," says Whitney English, RDN, a Los Angeles-based nutritionist and founder of the practice Whitney E. RD. What Are the Different Stages of Fasting? The idea is that it's easier to sharply restrict calories a few days a week or to limit eating to a shortened "eating window" each day than it is to moderately cut calories at every meal, every day. Contact your doctor right away if you notice signs and symptoms of diabetes mellitus, including unwanted weight loss and sweet, fruity-smelling urine. It can cause bad or fruity-smelling breath for people on a keto diet. The byproducts of burning fat, called ketones, cause your urine to smell sweet or fruity. They typically occur during the first few days of a fasting protocol (5).