40pc of young women too thin
The proportion of young Hong Kong woman who are underweight nearly doubled over the past 15 years, leaving more women at risk of developing the bone disease osteoporosis, according to a study by a Queen Mary Hospital doctor.
Dr Annie Kung Wai-chee found the percentage of 20- to 29-year-old women monitored from 2005 to 2010 who could be classified as having low body weight was nearly 40 per cent, up from 23 per cent in a 1995-2000 study conducted by the hospital's osteoporosis centre.
Kung used the World Health Organisation's classification of a body mass index (BMI) - calculated by dividing a patient's weight by their height squared - as the basis of her study. It says an index of 18.5 to 22.9 is normal.
In other words, four in 10 Hong Kong young women included in the study's most recent phase had a BMI that was lower than 18.5.
Kung said weight-conscious women were getting thinner and exposing themselves to an increased risk of osteoporosis, a decrease of bone tissue and loss of bone density over time.
'When a female is in puberty and she tries to control her body weight by eating less, she can't get enough calcium and vitamins to sustain bone growth,' she said.
Low body weight, smoking and too little calcium in the diet are all possible contributors to the disease. Apart from brittle bones, it also causes height loss and stooped posture.
Researchers monitored the BMI of women in various age groups in two phases, with 1,080 in the earlier group and 550 in the latter.
Similar increases were also seen among other age groups. About 30 per cent of those 80 or older were found to be underweight in the second phase, many more than the 6 per cent in the first phase.
Kung described the consequences as extremely serious and cited the experience of one of her patients as an example.
'Four years ago she weighed 36.3 kilograms and her BMI was 14. One day she slipped on a wet floor and broke her left leg,' Kung said. The patient was diagnosed with osteoporosis after surgery. 'A minor accident like this wouldn't cause such serious consequences to youngsters with normal bone density,' Kung said.
The then 19-year-old woman ate two meals a day but only dry food. After four years of treatment, she now weighs 41kg. Even though she was still underweight, Kung said, the disease was being managed.
'If a person has been underweight for more than a year, it's very difficult for body weight to resume to a normal level because of psychological factors and dieting habits,' Kung said.
To avoid developing osteoporosis, the doctor said women should maintain a healthy body weight through a balanced diet and regular exercise. She advised those whose BMI was less than 18.5 to have a bone-density check.
The Osteoporosis Society of Hong Kong says 300,000 women and 100,000 men suffer from the disease.
Portion of Hong Kong women aged 35 to 55 who never had a bone-density check, according to the Asian-Pacific Osteoporosis Foundation