1. Weight loss due to gastrointestinal or digestive diseases and disorders

If you have a condition such as irritable bowel syndrome, celiac disease, Crohn's disease or colitis, you may have persistent diarrhea or other GI complications. These are likely symptoms of malabsorption and may lead to weight loss. A gastroenterologist can confirm or rule out the presence of these diseases. Viral and bacterial infections, hormonal changes and various digestive disorders can all make you nauseated.

2. Hyperthyroidism causing weight loss

When the thyroid gland overproduces certain hormones, unexplained weight loss may occur. The thyroid hormones regulate every aspect of your metabolism, from your heart rate to how quickly you burn calories. When your thyroid gland produces too much of the hormone thyroxin, you develop hyperthyroidism. This condition causes sudden weight loss, even when your appetite is bigger than normal.

3. Medication and a resulting weight loss

Certain types of medication, including some antidepressants, have been known to cause unexpected weight loss. Read the accompanying packaging on your prescription medications and talk to your pharmacist or doctor if you suspect this might be the cause of your weight loss.

4. Weight loss as a result of diabetes or cancer

In some cases, undiagnosed diabetes is often preceded by unexplainable weight loss. Diabetes affects the way your body uses blood sugar. Even when you eat as much as usual, you may lose weight if your muscle tissues don't get enough glucose to generate growth and energy. This is especially true with type 1 diabetes, in which very little sugar gets into your cells. With uncontrolled diabetes, sugar lost in the urine may also contribute to weight loss.

With certain types of cancer, both the disease and the treatments may contribute to weight loss. With either diabetes or cancer, you might not "feel sick," but losing weight could be an indication that you are sick. . Many types of cancer cause unintentional weight loss, including cancers of the pancreas, gallbladder and stomach. Cancer treatment may have the same effect.

5. Changes in diet or activity level.

Skipping meals, eating on the run, eating less fat or preparing food in new ways may contribute to unexpected weight loss. A particularly hectic schedule may cause you to drop a few pounds as well.

What should you do if you are losing weight unintentionally? Losing more than 10% of your weight over a period of six months is cause for concern. If this happens, you should talk to your doctor, regardless of how old you are.

You can also loose weight due to stress, anxiety and Poor diet