Q: I am a 14-year-old girl and, at 1.68m, am taller than my mum. Yet, I weigh only 47kg. I feel weak all the time and can't even carry my baby sister for more than 60 seconds.

I find it hard to stand for an hour if I have to wait in line without leaning on something the whole time and taking occasional sitting breaks. I play softball but I never have enough energy to go on for more than one inning without feeling tired and weak.

My family is always picking on me because of how I eat. For instance, I don't like any veggies except beans and mashed potatoes or fries. As far as fruits go, I only like green apples; it makes me sick to eat anything else. I absolutely hate salads and I can't stand breakfast foods.

I also hate yogurt and I am not too fond of milk either. I hate being this skinny because my spine pokes out of my tee and when I wear a bikini, my ribs can be seen.

I used to have some flesh on my bones but then I grew taller without gaining much weight.

I am always feeling cold and I have been having a lot of headaches lately and a lot of cramps in my arms and legs.

What can I do to gain weight?

A: It seems that your dietary intake is quite poor and it can result in poor weight gain. From your account, you seem to be suffering from frequent muscle cramp, weakness and lethargy.

You may be suffering from hormonal imbalances such as thyroid disorders and diabetes mellitus. These hormonal conditions may also result in irregular menses. Another condition that could be a cause for concern is Marfan Syndrome, one that is associated with people of slim and tall stature.

You should consult a gynaecologist who sub-specialises in adolescent health. You will find such specialists at KK Women's and Children's Hospital or the National University Hospital. What you are experiencing is not uncommon, so do not be unduly worried about seeing a specialist.

In the meantime, do start taking some dietary supplements such as multi-vitamins that contain iron, folic acid, vitamin B12 and calcium. These vitamins are mentioned as they could be deficient in your diet and attributing to your symptoms. Iron-deficiency anaemia can result in lethargy and easy fatigability.

Your parents should accompany you to the initial consultation with the gynaecologist. The gynaecologist may want to explain his or her findings to them as well.

Your first consultation will likely include an assessment of your physical and psychological health and some blood tests for hormone analysis and exclusion of anaemia. You may also be referred to a dietitian who will advise you on how you should eat.

Dr Robin Tan

This article was first published in Mind Your Body, The Straits Times on Oct 23, 2008.