When you try to lose weight yourself eg by dieting and exercise, it is called Intentional weight loss.

When you lose weight even if you don't want to, it is called Unintentional weight loss.

You may have lost your appetite, so that you lose weight because you are eating less.

It can even so happen that you lose weight in spite of eating more! Don't be too happy about it because you may have an underlying health problem.

Causes of unintentional weight loss

Weight loss with reduced appetite

Anorexia nervosa

Depression

Drugs - metformin, amphetamine, cocaine, morphine

Alcohol

Hormone problems - eg underactive adrenal glands

Infections - TB, brucellosis, HIV, infective endocarditis

Cancer

Chronic heart failure

COPD

Weight loss with increased appetite

Increased physical activity.

Malabsorption - eg coeliac disease

Overactive thyroid

Type1 diabetes - untreated or inadequately treated

What to do

If you lose weight unintentionally, then get yourself checked out by your doctor.