Malnutrition can lead to chronic fatigue, which is one of the most common signs of malnutrition. When individuals don't consume enough calories and protein, their muscles and brain don't have the energy they need to function. It's common to feel physical fatigue and pain in the muscles. It's also common to sleep more than the average person, take naps, and constantly feel exhausted. Various micronutrient deficiencies can also lead individuals to tiredness and an inability to concentrate. They can experience impaired cognitive function and even potential brain damage if the nutrient deficiencies last for too long.
Fatigue can be caused by other underlying medical conditions as well, some of which can be potentially life-threatening if left untreated. Some of the most common nutritional deficiencies that lead to fatigue are lack of iron, vitamin B12, folic acid, potassium, and magnesium. Iron is the most common nutritional cause of fatigue. Individuals are more likely to suffer from an iron deficiency if they follow a vegetarian or vegan diet, so it's important to make sure they have some iron sources in their diet.