Cancer risk and obesity – the numbers are increasing

The latest obesity report from the WHO’s Regional Office for Europe (European Regional Obesity Report 2022) shows that people in Europe are getting fatter and fatter. More than half of adults in Europe are overweight or severely obese, which is referred to as obesity or obesity. It is estimated that obesity is also responsible for around 200,000 new cancer cases per year in Europe.

In Germany, 57 percent of adults are overweight and obese – 65 percent of men and 49 percent of women; 22 percent of them are overweight – 24 percent men and 20 percent women.

Body weight: what is normal? what is too much

Normal weight – overweight – obesity: The formula for calculating BMI and a table of weight categories for adults based on BMI © Krebsinformationsdienst, DKFZ

It is natural: For people with a normal body weight, the probability of getting a disease caused by excess weight is lower than for obese people. But what is normal weight and when do we talk about overweight and obesity and what effects does this have on the risk of disease?

Weight categories: For this purpose, the so-called Body Mass Index (BMI) is used in a simplified form, which takes body weight in relation to height. BMI is used to estimate body fat percentage and to classify it into the different weight categories. People in Europe are considered overweight if their BMI is over 25 kg/m² and obese or obese if they are over 30 kg/m². The higher the BMI, the greater the risk of obesity-related sequelae.

The waist circumference factor: The visceral adipose tissue that surrounds the organs in the abdominal cavity also appears to be of particular health importance. Since BMI does not allow any statements about body fat distribution, waist circumference or waist-to-hip ratio can also be used to assess the risk of being overweight.

To put it simply, a waist circumference of more than 102 centimeters in men and more than 88 centimeters in women indicates too much belly fat – although body type, ethnic origin and age are not taken into account here. More precise measurement methods, such as computed tomography, are considerably more complex and not suitable for general use.

Obesity: what causes are known?

In addition to genetic predisposition, diet and lifestyle have a decisive influence on body weight. In everyday life, it is often not possible to break down enough calories due to predominantly sedentary activities and lack of exercise. Then it is enough to eat a little more over the years to gain significant weight. In adulthood, this together typically leads to persistent weight gain and obesity.

Epigenetic factors, the gut microbiome and psychosocial factors may also influence the development of obesity. This is still being researched.

Obesity and cancer: The connections are complex

Person with branded organs who have an increased risk of obesity-related cancer.

Cancer associated with obesity © Krebsinformationsdienst, DKFZ, created with BioRender.com

Severe overweight in the sense of obesity can be seen as a complex, multifactorial, chronic disease. This accumulation of fat, which exceeds the normal level, poses a risk in adults for cardiovascular disease, type 2 diabetes mellitus, liver disease and also cancer.

These cancers are affected: According to the International Agency for Research on Cancer (IARC), at least 13 types of cancer have been shown to be related to excess body fat (see figure opposite). The connection between severe obesity and the risk of cancer varies in strength and depends, among other things, on the type of cancer, gender and age. A connection is suspected for some other forms of cancer.

What leads to the development of cancer? The biological mechanisms underlying the development of cancer in overweight and obesity are intensively researched. There are still many questions about the link between obesity and cancer. One thing is already clear: the fat cells (adipocytes) receive messenger substances and release hormones themselves. Depending on the type and activity of these processes, metabolic disturbances, dysregulation of sex hormones, increased formation of insulin and insulin-like growth factors, inflammatory reactions and oxidative stress in the adipose tissue can occur.

Obesity in Europe: future prospects

It is likely that no European country will be able to stop the rise in adult obesity in the next few years. The proportion of overweight and obese children in Europe is already relatively high: 29 percent of children aged 5 to 9 are overweight, of which 11 percent are obese. 25 percent of 10 to 19-year-old children and young people are overweight, of which 8 percent are obese. It is possible that these numbers will continue to rise due to changes in food consumption and lack of physical activity during the corona pandemic.

Further research needed: The previous database on obesity-related diseases in adulthood was usually collected from adults who had a normal body weight during childhood. It is not yet known with certainty whether obese children have a higher risk of remaining obese in adulthood. Whether childhood obesity is a risk factor for cancer in adulthood is not sufficiently proven with the data available to date. Further studies on this question must follow.

Obesity Cancer Prevention: There is increasing evidence that, at least in some European countries, obesity may replace smoking as the main risk factor for cancer in the future. Effective prevention strategies and solutions for people at high risk are therefore more necessary than ever before:

  • Maintaining a normal body weight throughout life is an important step in reducing the risk of obesity-related diseases such as cancer.
  • Policies at the societal level must increasingly aim to discourage people from consuming high-calorie foods and encourage the consumption of fruit and vegetables.
  • In addition, more incentives for physical activity should be created.

The experts’ hope: Results from research into the link between obesity and cancer will help to establish further effective strategies for prevention and therapy in the future.

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