When your BMI scale shows a number less than 18.5, then you are underweight. Obesity is known for the health complications associated. Unfortunately, no one cares to find what the complications are being underweight are. Being underweight is common in women and girls, especially who are after the skinny looks. Obesity and being underweight both can result in health complications and are risky. Infections, osteoporosis, and fertility issues are examples of the health complications caused if you are underweight. You need to gain adequate weight by eating healthy. Do you know what your diet should consist of for this? Find from this quiz.