Some weight changes in life are expected. For example, people may lose weight if they change their exercise or eating habits.
But weight loss can happen for reasons that you would not usually expect. For example, medical problems can cause unplanned weight loss. These include problems with your thyroid gland, long-term infections, mouth or throat problems that make it hard to eat, and digestive problems. They also include depression and cancer. Some medicines also may cause you to lose weight.
Talk to your doctor if you have unplanned weight loss. Your doctor may suggest making changes in what you eat to help you gain back the weight you lost. The doctor may also refer you to a dietitian.