Link between overweight obesity and cancer
Many people believe that cancer is primarily an inherited disease, however this is not the case. In fact, the World Cancer Research Fund (WCRF) estimate that about 40% of cases of cancer could be prevented by improving diet, body weight, reducing alcohol and increasing physical activity.
Scientific research confirms that there is a strong link between increased body fatness several types of cancer including cancers of the breast (after menopause), gallbladder, oesophageus, pancreas, ovaries, endometrium, kidney, thyroid, colon and rectum. In fact, the WCRF estimate that 20% of these types of cancer could be prevented simply by maintaining a healthy weight alone. There are several potential ways in which body fatness increases the risk of cancer. For example, body fatness increases the level of certain cancer promoting hormones such as insulin, leptin and estrogen (in females) in the body. In addition, being overweight is associated with low-grade inflammation, which might also promote cancer development.
Maintaining a healthy weight after a cancer diagnosis is also associated with improved cancer survival. A recent review of eighty-two studies1, which included 213,075 pre and post menopausal breast cancer survivors, found that obese women had a 41% and overweight women a 7% increased risk of dying from breast cancer regardless of whether women were overweight at the time of their diagnosis or they gained weight afterwards. The authors conclude that randomised clinical trials are urgently needed to test the effect of different weight loss strategies on survival in cancer.
Research also shows that the best “cancer protective” diet is one that is based on plant foods. Vegetables and fruits are believed to be protective against a range of cancers, including mouth, pharynx, larynx, esophagus, stomach, lung, pancreas and prostate. Vegetables and fruits may protect against cancer for several reasons. In addition to containing vitamins and minerals, which help keep the body healthy and strengthen our immune system, vegetables and fruits are good sources of protective compounds like antioxidants and phytochemicals, which can help to protect cells in the body from damage that can lead to cancer.
Plant foods also contain fiber, which is linked to a reduced risk of cancer. Fiber is thought to have many benefits related to cancer prevention, such as helping us to maintain a healthy weight. This is because fiber makes us feel fuller after eating and because high fiber foods are generally lower in calories. Fiber also helps speed up the time it takes food to move through the digestive system and potentially absorbs other cancer causing compounds such as HCAs and PCAs which are produced when meat is cooked at high temperatures, and nitrates which are used as preservatives in some meats. Foods high in fiber include whole-grain bread and pasta, oats and vegetables and fruits.
Written by Dr Kellie Bilinski. Accredited Practising Dietitian. APD, PhD
1 Annals of Oncology 00: 1–14, 2014