Media release
From: European Congress on ObesityBody mass index during childhood linked with risk of anorexia nervosa and bulimia nervosa in later life
Danish study of more than 66,000 girls finds low body mass index in girls as young as 7 years may be a risk factor for developing anorexia nervosa as adults, while high childhood BMI may be a risk factor for bulimia nervosa
New research being presented at The European Congress on Obesity (ECO) held online this year, suggests that among girls a low body mass index (BMI) during childhood indicates a higher risk of developing anorexia nervosa as young adults, whereas a high BMI or overweight in childhood indicates a higher risk of bulimia nervosa.
"By examining the records of thousands of girls over their lifetime in national health registers, we have discovered early warning profiles that could signal girls at risk for anorexia nervosa and bulimia nervosa", says lead author Dr Britt Wang Jensen from Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark. "The difference in childhood BMI of girls who later developed eating disorders started to emerge at an early age. These results highlight the importance of regularly monitoring weight and height during childhood to identify these patterns as early as possible."
In the UK, the annual number of new cases of anorexia nervosa among 8 to 12-year-olds doubled from 1.5/100,000 in 2006 to 2019 to 3.2/100,000 [1]. Whether premorbid (pre-illness) BMI is associated with anorexia nervosa and bulimia nervosa is unclear. So far, studies have reported conflicting findings, with some suggesting that a high BMI precedes both diseases, whereas others suggest that a low BMI precedes anorexia nervosa and a high BMI precedes bulimia nervosa.
To explore this further in a population-based cohort, Danish researchers analysed data for 66,576 girls from the Copenhagen School Health Records Register born between 1960 and 1996 who had information on height and weight measured at annual school health examinations from ages 7 to 13 years. Cases of anorexia nervosa and bulimia nervosa were identified by linking with the Danish National Patient Register and the Danish Psychiatric Central Research Register. The girls were followed from ages 10 to 50 years.
During the study, 514 women were diagnosed with anorexia nervosa at an average age of 20 years, and 315 women were diagnosed with bulimia nervosa at an average age of 23 years.
The analyses suggest significant "inverse associations" between childhood BMI and the risk of anorexia nervosa in later life, which means that the risk of anorexia nervosa fell as BMI increased. For example, when comparing two 7-year-old girls with an average height and one z-score difference in BMI (equivalent to 2.4 kg), the girl with the higher BMI had a 14% lower risk of developing anorexia nervosa than the girl with the lower BMI; at age 13 years the risk was 28% lower.
In contrast, significant and positive associations were observed between childhood BMI and the risk of bulimia nervosa. For example, when comparing two 7-year-old girls with an average height and one z-score difference in BMI (equivalent to 2.4 kg), the heaviest girl had a 50% higher risk of bulimia nervosa than the leaner child in later life; at age 13 years the risk was 33% higher.
In addition, compared to girls with normal weight at age 7 years, girls with overweight had twice the risk of developing bulimia nervosa in later life; at age 13 years the risk remained but was lower. The associations did not vary by age at diagnosis.
The authors say that further studies are needed to uncover the mechanisms underlying these associations. They acknowledge that the findings are associations only, and point to several limitations, including that diagnoses in this study may be more severe cases as they are based on hospital admissions and contacts, which may limit the generalisability of these findings to less severe forms of these eating disorders. Moreover, the analyses were restricted to girls as there were too few cases to analyse among boys.
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Higher BMI in childhood may help protect women against breast cancer in later life, both before and after the menopause
A study of more than 173,000 women in Denmark, presented at The European Congress on Obesity (ECO) held online this year, suggests that girls with a higher body mass index (BMI) during childhood are less likely than their peers with a lower BMI to develop breast cancer as adults, both before and after the menopause.
The findings contrast with those for adult BMI, which indicate that women who gain weight after menopause have an increased risk of postmenopausal breast cancer. While the authors are unsure why children with a higher BMI appear to be protected against breast cancer, they caution that having overweight or obesity can have many 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", says lead author Dr Dorthe Pedersen from Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark. "There are so many health risks linked with having overweight or obesity, it is vital for women to maintain a healthy weight throughout their lives."
Breast cancer is the most common cancer in women, with around 55,000 women diagnosed every year in the UK alone, and almost 1 in 5 cases developing in those under the age of 50. Previous research has established a link between increased BMI in adult women and a lower risk of breast cancer before the menopause, but an increased risk after menopause. Although a high childhood BMI may be protective against the risk of overall breast cancer, past studies had not been large enough to investigate the link by type menopausal status.
To provide more evidence, Danish researchers analysed data for 173,373 women from the Copenhagen School Health Records Register born between 1930 and 1996 (aged 25 to 91 years now) who had information on height and weight measured at annual school health examinations from ages 7 to 13 years. Cases of breast cancer were identified by linking with the Danish Cancer Registry.
During an average of 33 years of follow-up, 4,051 women were diagnosed with breast cancer before the menopause (at 55 years of age or younger), and 5,942 women after the menopause (after age 55 years).
The analyses suggest "inverse associations" between childhood BMI and breast cancer risk before and after the menopause, which means that breast cancer risks decreased as BMI increased. For example, when comparing two 7 year-old girls with an average height and one z-score difference in BMI (equivalent to 2.4 kg), the girl with the highest BMI had a 7% lower risk of developing pre-menopausal breast cancer and a 10% lower risk of developing post-menopausal breast cancer than the girl with the lower BMI.
The authors say that further studies are needed to uncover the mechanisms underlying these associations. They acknowledge that the findings are associations only, so no conclusions can be drawn about cause and effect, and point to several limitations, including that the study used BMI as a marker of fat mass, but children with the same BMI can have different body fat distributions and overall levels of body fat.
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Higher BMI, body fat, and larger waist and hips pose similar risk for 10 common cancers in study of over 400,000 UK adults
New estimates also suggest substantial proportion of common cancers could be prevented by reducing obesity, including 44% of endometrial and 39% of uterine cancers in women, and 22%, 18% and 17% of kidney, stomach and liver cancer in both men and women, respectively
Obesity increases the risk of developing 10 of the most common cancers, regardless of how it is measured, according to a study of more than 400,000 adults in the UK, being presented at The European Congress on Obesity (ECO) held online this year. With central fatness (larger waist and hips) and general obesity (body mass index [BMI] and body fat percentage) associated with similar estimates of cancer risk.
The results suggest that BMI is an adequate measure of cancer risk from excess weight, and there is no advantage in using more complicated or expensive measures such as waist circumference or body fat percentage.
It is well known that being overweight or obese is linked to an elevated risk of some cancers and premature death. However, most of the evidence is based on BMI, and little is known about the association between cancer and other markers of adiposity (eg, central obesity and body fat).
Using data from the UK Biobank prospective cohort study, researchers from the University of Glasgow identified 437,393 adults (54% women; average age 56 years) who were cancer-free, to investigate the risk of developing and dying from 24 cancers according to six markers of obesity: BMI, body fat percentage, waist-to-hip ratio, waist-to-height ratio, and waist and hip circumferences.
The results were adjusted for age, sex, ethnicity, deprivation, education, smoking, alcohol consumption, intakes of fruit and vegetables, red and processed meat, oily fish, physical activity, and sedentary behaviours [1]. After an average of 9 years follow-up, there were 47,882 cases of cancer, and 11,265 cancer deaths.
The researchers found that all six obesity measures were positively and similarly associated with higher risk for 10 cancers. For example, each 4.2 kg/m2 (men) and 5.1 kg/m2 (women) increase in BMI above 25 kg/m2 (defined as being overweight) was linked with higher risk of cancers of the stomach (35% increase), gallbladder (33%), liver (27%), kidney (26%), pancreas (12%), bladder (9%), colorectal (10%), endometrial (73%), uterine (68%), postmenopausal breast (8%), and overall (3%) cancer.
Based on the results, the researchers estimate that if these associations were causal, being overweight or obese could be responsible for around 40% of endometrial and uterine cancers and 29% of gallbladder cancers; and could account for 64%, 46%, and 40% of deaths from these cancers respectively (figure 8).
"We observed a linear association - the more severe obesity is, the higher the risk of developing and dying from these cancers, except for postmenopausal breast cancer", says Dr Carlos Celis-Morales from the University of Glasgow, UK, who led the research. "But there was a lot of variation in the effects of obesity on different cancers. This tells us that obesity must affect cancer risk through a different number of processes, depending on the cancer type."
This is an observational study, so can't establish cause, and the researchers say they cannot rule out the possibility that other unmeasured factors (residual confounding) may have influenced the results. They also note that the study is not a representative sample of the UK adult population, so the results might not be generalisable to the general population.
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Combining BMI with body shape better predictor of cancer risk, suggests UK study in over 440,000 adults
But body shape may increase risk of liver, lung, and bowel cancer, regardless of BMI
New research being presented at The European Congress on Obesity (ECO) held online this year, suggests that a measure of body shape should be used alongside body mass index (BMI) to help determine the risk of obesity-related cancers.
BMI is a simple way of measuring body fat from the weight and height of a person. But its reliability is often criticised, because it does not distinguish fat from muscle, or take into account where body fat is stored or an individual's sex or age. Similarly, waist circumference takes into account belly fat, which is linked to several health risks including cardiovascular disease, type-2 diabetes and cancer, but fails to account for height.
A new metric to measure obesity, called 'A body shape index' (ABSI), takes into account an individual's age, sex, weight, height and waist circumference-and it may provide a more accurate estimate of cancer risk than BMI.
To explore this further, researchers from the University of Glasgow and the University of Newcastle, combined data from 442,614 participants (average age 56 years) from the UK Biobank prospective cohort who were followed for an average of 8 years, during which 36,961 individuals were diagnosed with cancer.
Participants were broken down into three groups (tertiles) according to their body shape to examine the associations with the risk of 24 different types of cancer; and to examine ABSI and BMI as predictors of cancer risk. Results were adjusted for age, sex, ethnicity, deprivation, education, income, smoking, alcohol consumption, dietary intake, physical activity, and sedentary time.
The analysis found that body shape and BMI predicted different obesity-related cancer risk in adults. Specifically, ABSI was linked with an increased risk for three cancers. Participants in the highest ABSI tertile were 38% more likely to develop liver cancer, 40% more likely to develop lung cancer, and had a 17% increased risk of bowel cancer, compared to those in the lowest ABSI tertile, regardless of BMI.
However, researchers found that high ABSI and high BMI combined were linked with an increased risk for seven different types of cancer-uterine, oesophageal, liver, stomach, kidney, bowel, breast cancer. For example, participants in the highest ABSI tertile who were also overweight or obese (BMI 25 kg/m2 or over) were at twice the risk of developing uterine cancer than those with the lowest ABSI and normal BMI.
"Our findings underscore the importance of measuring more than just BMI when predicting cancer risk, and suggest that people's body shape may increase their risk of certain cancers", says lead author Dr Carlos Celis-Morales from the University of Glasgow, UK. "Whatever method you use, being overweight or obese is the single biggest preventable cause of cancer after smoking. More urgent actions are needed to help people maintain a healthy bodyweight and shape throughout their lives, starting at an early age."
Having excess body fat can lead to biological changes that alter levels of sex hormones, such as oestrogen and testosterone, cause levels of insulin to rise, and lead to inflammation, all of which have been linked with increased risk of 13 different types of cancer.
This is an observational study, so cannot establish cause, and it is not a representative sample of the UK adult population, so the results cannot be generalised to the general population.
