Childhood BMI linked with risk of anorexia nervosa, bulimia nervosa and breast cancer in later life

Findings published at the European Congress on Obesity (ECO) found major links between childhood body mass index (BMI) and the risk of developing eating disorders like anorexia and bulimia, as well as breast cancer in adulthood.

According to one presentation at the ECO, girls with a low body mass index (BMI) during childhood were found to be at higher risk of anorexia nervosa in adolescence and beyond, while those with a high BMI were linked to a higher risk of developing bulimia nervosa in later life.

The researchers examined data for 66,576 girls from the Copenhagen School Health Records Register born between 1960 and 1996, all of whom were regularly monitored for changes in their BMI.

The girls had their height and weight measured at annual school health examinations from ages 7 to 13 years. This data was then cross referenced against the Danish National Patient Register and the Danish Psychiatric Central Research Register. The women were then monitored intermittently from the age of 10 to 50. 

Some 514 women were diagnosed with anorexia, on average around age 20, while 315 women were diagnosed with bulimia nervosa, on average around 23 years of age. 

The findings uncovered “early warning profiles that could signal girls at risk for anorexia nervosa and bulimia nervosa" according to lead author Dr. Britt Wang Jensen from Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark.

This field of study has proven challenging, however, with studies suggesting different results, some reporting that high BMI precedes both anorexia and bulimia, while others suggesting low BMI precedes anorexia and high BMI precedes bulimia.

The researchers also found significant "inverse associations," wherein a girl with a higher BMI than an age and height-matched peer had a 14% lower risk of developing anorexia nervosa than her lower BMI contemporary.

The authors also compared two 7-year-old girls of average height, with a 2.4kg difference in weight, and found the heavier girl had an incredible 50% higher risk of developing bulimia nervosa in later life. 

When compared with girls within the 'normal' weight range at age seven, overweight girls had twice the risk of developing bulimia. 

The authors admit freely that they don't yet understand the mechanisms which guide these associations and that more study is urgently needed. 

Meanwhile, another study of more than 173,000 women in Denmark, also presented at the European Congress on Obesity, suggests that girls with a higher body mass index are less likely to develop breast cancer in adulthood, irrespective of whether they are pre- or post-menopause.

The authors in that study cautioned that while their findings suggest higher childhood BMI affords some degree of protection against breast cancer in later life, it also increases adverse impacts on general health. 

"Our results suggest that having a higher BMI during childhood may lower your risk of breast cancer both before and after the menopause. But we must be really clear that weight gain should not be considered as a way of preventing breast cancer," said lead author Dr. Dorthe Pedersen from Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark.

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