There are several common diseases that can lead to the inability to gain weight -- but there could also be a simpler explanation, such as not getting enough calories in your diet. Knowing what signs and symptoms to look for can help determine if your lack of weight gain is caused by your lifestyle, or is the result of an underlying disease. Contact a doctor if you are experiencing unexplained weight loss.
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Many people who can't gain weight don't realize they are not getting enough calories to gain weight. Skipping meals due to a busy schedule or simply not consuming enough of the right foods, such as fats or carbohydrates, can be factors. Exercising but not consuming enough calories to make up for the expenditure is another common reason you might not gain weight. Monitoring your daily caloric expenditure and intake can help determine if this is the case.
The thyroid gland affects your metabolism through the hormones it secretes. When it produces too much thyroxin, your metabolism will speed up and you will burn calories more rapidly -- a condition known as hyperthyroidism. Your appetite will often increase, and you may not gain weight despite eating more. Other symptoms can include a rapid or irregular heartbeat, nervousness, anxiety, tremors in the hands and fingers and an increase in bowel movements. Women may see a change in menstrual patterns. You may also feel an enlargement in your neck. Muscle weakness, weight loss and fatigue are also common symptoms. If you experience any of these symptoms, contact a doctor immediately.
There are two types of diabetes. Type 1 is usually diagnosed in childhood but can also be diagnosed later in life -- it is caused by a lack of insulin in the body. Type 2 diabetes is marked by resistance to insulin and usually occurs in adulthood. Insulin regulates the amount of glucose in the body, so weight and appetite are often the first things affected because glucose is our main source of fuel. Both types can lead to lack of weight gain, even with an increased appetite. Other symptoms of diabetes can include blurred vision, fatigue as well as increased appetite, thirst and urination. If you have any of these symptoms, contact a doctor.
Problems with the intestines can mean your body is not properly absorbing the food you are eating. Even if you are consuming a lot, you could have malnutrition and not be able to gain weight. These types of diseases are known as "malabsorption syndromes." Some common forms of this disease type are irritable bowel syndrome, Crohn's disease, ulcers and celiac disease, according to the Mayo Clinic. Symptoms can include blood in the stool, abnormal bowel movements -- too many or too few -- fatigue, pain in the abdomen, gas and possible weight loss. If you are experiencing these symptoms along with no weight gain, consult a doctor for proper diagnosis.
Hyperthyroidism, diabetes and gastrointestinal problems are the common diseases that can lead to losing weight or the inability to gain weight. But there are other, less-common, issues that could be at fault. Some prescription medications can increase your metabolism, which will burn more calories. Cancer, infection and neurological issues can all affect your weight, usually in the form of weight loss. Regardless, it's best to consult a doctor to get a proper diagnosis. Even if it ends up that you are one of those who simply has a hard time gaining weight, knowing what is at the root of the problem can offer relief and give you an indication of what your next step should be.