YOU CAN REDUCE YOUR RISK OF CANCER BY MAINTAINING A HEALTHY BODY WEIGHT

As a result of years of research into the topic, there is now general consensus among scientists, health professionals, and policy-makers that there is a close association between food, nutrition, physical activity, body composition, and the risk of cancer. It is now clear that cancer is, in large part, a preventable disease.

The World Cancer Research Fund (WCRF) expert report on: Food, Nutrition, Physical Activity and the Prevention of Cancer, released in November 2007, presents the evidence for this link and provides detailed recommendations for the prevention of cancers.
The maintenance of a healthy weight throughout life is one of the most important ways to protect against cancer.

In the NutriScene write up of September 14, I had summarised all the eight general recommendations and two special recommendations of the WCRF report.

In this instalment, I will look at the first recommendation: be as lean as possible within the normal range of body weight. The report discusses the evidence of being overweight or obese and increased risk to some cancers. Various specific recommendations were made in relation to reducing body fatness.

The report highlights that maintenance of a healthy weight throughout life is one of the most important ways to protect against cancer.

The evidence

You are aware that cancers can be caused by various toxic chemicals in foods and drinks. You have heard that consuming too much of certain foods increases the risk to certain cancers. It is less well known that overweight and obesity can increase the risk to cancers.

The evidence linking overweight, obesity and cancer is now even stronger than it was in the mid-1990s. There is now convincing evidence that excess body fat increases the risk of the following cancers: colorectal (bowel), oesophagus, pancreas, kidney, endometrium (womb) and breast (in postmenopausal women). Being overweight or obese probably also increases the risk of gallbladder cancer. There is limited evidence suggesting that greater body fatness is a cause of liver cancer.

It is not just the increase in body weight that increases risk to cancers. We also know that where we store extra weight affects cancer risk. Scientists have discovered that carrying excess fat around our waists can be particularly harmful. This is strongly linked to colorectal (bowel) cancer and probably to cancers of the pancreas and endometrium (womb), as well as breast cancer (in postmenopausal women).

There could be several reasons for this link between overweight, obesity and cancer. One example is the relationship between excess fat and the hormonal balance in the body. Research has shown that fat cells release hormones such as oestrogen, which increases the risk of cancers such as breast cancer.

While the exact mechanism for this cause of cancers is unclear, it is however certain that taking steps to avoid becoming overweight or obese is one of the most important things we can do to reduce our cancer risk.

WCRF recommendations

The recommendation of WCRF is therefore to be as lean as possible within the normal range of body weight.

The public health goals, which are for populations and are therefore principally for health professionals, are:

a)Median adult body mass index (BMI) to be between 21 and 23, depending on the normal range for different populations.

b)The proportion of the population that is overweight or obese to be no more than the current level, or preferably lower, in 10 years.

The personal recommendations, for people as communities, families, and individuals are:

a)Ensure that body weight through childhood and adolescent growth projects towards the lower end of the normal BMI range at age 21.

b)Maintain body weight within the normal range from age 21.

c)Avoid weight gain and increases in waist circumference throughout adulthood.