Smaller feet may be caused by different shoe size standards, weight changes, and disuse atrophy. 1. Different shoe size standards: due to the irregularity of the shoe size of the shoes bought, or different brands and types of shoes can also cause certain differences, so it is not necessarily that the feet become smaller, but the shoe size standards are different. 2. Weight change: it may be due to significant weight loss, which will lead to local muscle reduction, especially for obese weight loss people, there may be a foot smaller. 3. Wasting atrophy: Due to long-term bed rest and reduced activity, it may lead to wasting atrophy of the muscle tissues of the feet . Or the bones of the feet are decalcified, which affects the normal absorption of nutrients by the muscles of the feet, and therefore leads to smaller feet. If the smaller feet are not caused by shoes and weight changes, you should go to the hospital in time and ask the doctor for a clear examination and treatment.