Keep Your Weight Within the Healthy Range and Avoid Weight Gain in Adult Life

There is strong evidence that greater body fatness causes many cancers, and this evidence has strengthened over the last ten years. The risk is higher the more weight a person gains and the longer they are overweight for. Maintaining a healthy body weight throughout life is on the of the most important ways to protect against cancer.

There is now ‘convinving’ scientific evidence that being overweight or obese throughout adulthood increases the risk of: mouth, pharynx and larynx cancers, oesophageal cancer (adenocarcinoma), stomach cancer (cardia), pancreatic cancer, liver cancer, colorectal cancer, breast cancer (postmenopausal), ovarian cancer, endometrial cancer (cancer of the womb), prostate cancer (advanced) and kidney cancer. Greater weight gain in adulthood increases the risk of post-menopausal breast cancer.

Body fatness is difficult to measure directly without special equipment. Body Mass Index (BMI) is commonly used as a measure of weight in relation to your height. BMI is calculated as weight in kilograms divided by height in metres squared (kg/m 2 ). BMI charts and calculators are available online that can be easily used to classify your weight for height score. It is recommended that individuals keep their BMI within a healthy range. The World Health Organisation (WHO) have classified healthy or ‘normal’ weight adults as having a BMI of between 18.5-24.9kg/m 2 , underweight as <18.5kg/m 2 , overweight as >25kg/m 2 , and obese as >30kg/m 2 .

Where fat is stored in the body is also important. Storing fat around the abdomen (or belly) is commonly referred to as an ‘apple shape’. Excess abdominal/belly fat is a cause of a number of chronic diseases including type two diabetes, cardiovascular disease and many cancers.

Being overweight doesn’t mean that someone will definitely develop cancer. But if a person is overweight they are more likely to get cancer than if they are a healthy weight. Consistent results from decades of research involving millions of people show the strong link between obesity and cancer and means we can confidently rule out other reasons (such as chance or other lifestyle factors). The risk increases the more weight is gained.

There are many reasons why extra body fat is linked with cancer. For some cancers like oesophageal cancer, increased body fatness may promote acid reflux which may lead to damage or inflammation of the oesophagus, which over time can increase the risk of oesophageal cancer. For colorectal cancer, high body fatness is associated with changes in hormonal profiles, such as increased levels of insulin, which can promote the growth of colon cancer cells and prevent the body’s own natural way of killing off damaged cells. Higher levels of insulin and higher levels of inflammatory proteins in the blood as a result of obesity can also promote the development of many cancers including colorectal and postmenopausal breast cancer. In postmenopausal women with increased body fatness, higher levels of hormones like insulin and oestrogen (made in fat tissue) are in the blood. These are only a few examples of the role excess body weight can play in cancer development.


The best advice for maintaining a healthy weight is to be physically active, consuming a diet rich in wholegrains, fruit and vegetables, while limiting the consumption of sugar sweetened drinks and energydense foods (convenience foods) that are high fat, sugar and salt.

Plant foods are generally low in energy (with a few exceptions) and eating a large amount of plant food helps to control the amount of food and calories (energy) we consume. This in turn helps to prevent excess weight gain. Fruit and vegetables also form an important part of the diet to prevent against cancer development. It is best to choose whole, fresh fruit and vegetables, rather than processed or tinned foods that are high in sugar or salt. Red meat should be consumed in low to moderate amounts and processed meat should be avoided. Alcoholic drinks should also be consumed in small amounts, if not at all. Alcohol is very high in energy (calories) and has been shown to be linked to many cancers.

Being physically active daily helps to maintain a healthy weight, as well as improving cardiovascular fitness. It is recommended that individuals be physically active for at least 30 minutes every day. As fitness improves, this should be increased to 60 minutes or 30 minutes of vigorous activity, equating to approximately 150 minutes per week. Even standing up or getting up and about at work can help to increase the amount of time spent being active.