Eating less can cause constipation, because eating too little, resulting in poor gastrointestinal motility function, constipation will occur. Causes of constipation, in addition to eating less, include a variety of reasons, as follows: First, too little fiber intake, or often suppress the feeling of defecation. Second, drug factors: such as opioids, anticholinergics, anticonvulsants, can also cause constipation. Third, endocrine, metabolic diseases: such as hypothyroidism, hypercalcemia, etc. Fourth, neurological diseases: such as Parkinson’s disease, spinal cord injury, can lead to constipation. Fifth, psychological factors: such as depression, obesity-related psychological disorders, can cause slowed intestinal motility. Sixth, gastrointestinal diseases: such as pyloric obstruction, giant colon, psychogenic gastrointestinal disease, can lead to constipation due to slowed intestinal motility. When the symptoms of constipation appear, we should seek medical attention in time, under the guidance of a doctor, give a systematic examination, and give appropriate treatment according to different causes to prevent delays.