Being overweight or obese during early adulthood – between the ages of 18 and 40 – could be linked with up to 18 cancers, according to researchers at the World Health Organization‘s (WHO) International Agency for Research on Cancer (IARC).
The WHO researchers noted their findings in a cohort study of 2.6 million adults published in the Nature Communications, adding that some of the cancers were not previously associated to weight as a risk factor. They looked at data from these individuals who were aged 40 and younger who were cancer-free in 2009. Using advanced methodologies, they examined the body mass index (BMI) scores throughout the lifetime of people involved with the study – instead of focusing on one BMI measurement.
The people in the study were tracked for nine years to see whether they developed cancer and after nine years of follow-up, 225,396 participants were diagnosed with cancer. They found that apart from BMI at baseline, other BMI-derived indicators, such as duration, degree and age of onset of overweight and obesity were associated with the risk of up to 18 types of cancers.
The results of the study indicated that the longer the length of time, the greater the degree, and the younger the age of overweight and obesity – the higher the associated risk of developing 18 different cancers.
“Our findings seem to indicate that longer exposures to overweight and obesity (with or without accounting for the degree of overweight and obesity), as well as developing overweight and obesity at younger ages in early adulthood might increase cancer risk,” the authors wrote.
Previous evidence links excess weight to at least 13 cancers
Previous evidence from the World Cancer Research Fund (WCRF) and others have linked overweight and obesity to at least 13 different cancers:
- Brain and other central nervous system (meningioma or cancer in the tissue covering the brain and spinal cord)
- Thyroid
- Esophagus (adenocarcinoma of the esophagus)
- Breast (post-menopausal women)
- Liver
- Stomach
- Kidney
- Gallbladder
- Pancreas
- Bowel
- Ovary
- Uterus
- Myeloma (cancer of blood cells)
Now, excess weight has also been linked to leukemia, non-Hodgkin lymphoma and among people who never smoked – head, neck and bladder cancers.
Dr. Heinz Freisling from the IARC, one of the study’s co-leaders, said these cancers have not previously been “considered as obesity-related cancers” and that the impact of obesity on cancer is “likely underestimated.”
“Our own evidence shows that maintaining a healthy weight throughout life is one of the most important things people can do to reduce their cancer risk, and early prevention in adulthood is key,” said Dr. Panagiota Mitrou, WCRF director of research, policy and innovation.
How can being overweight or obese cause cancer?
Being overweight is a precursor to obesity. Extra fat in the body doesn’t just sit there – it’s active, sending out signals to the rest of the body. It can affect growth, metabolism and reproductive cycles.
These signals can tell cells in the body to divide more often, which can lead to cancer, explains general practitioner Dr. Dawn Harper in Stroud, Gloucestershire.
The National Cancer Institute notes that cancer is a large group of diseases that can start in almost any organ or tissue of the body when abnormal cells grow uncontrollably and go beyond their usual boundaries to invade adjoining parts of the body and/or spread to other organs.
According to research from the American Cancer Society, excess body weight is thought to be responsible for about 11 percent of cancers in women and about five percent of cancers in men in the U.S., as well as about seven percent of all cancer deaths.
Natural ways to achieve healthy body weight
For those who are overweight or obese, here are some lifestyle changes to consider toward the goal of achieving a healthy weight.
