How does being overweight or obese affect our cancer risk?

Research shows a direct link between being overweight and obese and 11 different types of cancer including bowel, breast (in postmenopausal women), gallbladder, kidney, liver, oesophagus (adenocarcinoma), ovary, pancreas, advanced prostate, stomach (cardia) and womb cancer. In England in 2015-2016, 62% of adults were overweight or obese. Even scarier, 28% of children from 2-15 years of age were overweight or obese. This alone is increasing their risk of developing cancer later in life before we even start talking about their dietary habits or physical activity levels.


There are a number of ways being overweight or obese can increase your risk of these cancers including:

  • Fat cells encourages the body to produce growth hormones which can promote the growth of cancer cells

  • The more overweight we are, the more fat cells our body stores. These fat cells produce hormones like oestrogen also which research shows increases the risk and promotes the growth of breast and womb cancer.

  • Fat cells can also stimulate the body to have an inflammatory response which may also increase the risk of several cancers.

So what should we do to reduce our cancer risk?

The World Cancer Research Fund International (WCRF) is the world's leading authority on the link between diet, weight, physical activity and cancer. The Continuous Update Project is an ongoing programme that the WCRF runs to continually analyse global research on these links and provide us with the most up-to-date guidance on what we can do on a daily basis within our normal lives to minimise the risk of cancer from lifestyle factors.  This is outlined in their 10 Cancer Prevention Recommendations. Their first recommendation is:

'Be as lean as possible without becoming underweight'

What is a healthy weight?

To determine if you are a healthy weight, we measure your weight and height to work out your Body Mass Index (BMI). You can do this using the BMI calculator below:


If your BMI is between 18.5-24.9kg/m² you are a healthy weight for your height. If it is less than this you are underweight and would benefit from gaining some weight to achieve a BMI in the healthy range. If your BMI is >25kg/m², you are carrying too much weight and can lower your cancer risk by losing weight. Checking your BMI is only an estimate and is not very accurate in older people, pregnant women, those with a high muscle mass like athletes, some ethnic groups and those less than 5 foot tall.

It is also important to understand the distribution of extra weight around your body as too much weight or fat around your stomach is associated with an increased risk of cancer, but also diabetes and heart disease. A healthy waist measurement for men is <94cm/37 inches and for women is <80cm/31.5 inches.

What can you do to be a healthy weight?

You can maintain your weight by balancing the amount of energy you take in through your diet and the amount of energy you expend through your body’s daily requirements and your daily physical activity. Think of it like a see-saw; if you consume more than you expend you will gain weight and vice versa. A typical man needs around 2500 calories per day and a woman needs around 2000 calories per day. If you take in more than this, you need to do more exercise to balance it out.

  • Losing just 5-10% of your weight has huge health benefits.

  • Small changes make a big difference in the long term

  • A weight loss of 0.5 to 2 lbs per week is a realistic goal

The following resources from the British Dietetic Association will provide you with practical ideas on how to be more active and eat more healthily to lose weight. However, you must first decide why you want to lose weight and change your lifestyle habits because it is important for success to choose a time that is right for you.



If you find it easier to stick to a structured meal plan to lose weight, most men will lose weight on a 1800 calorie per day meal plan most women will lose weight on 1500 calories per day. Ideally, you need to eat 500-600 calories fewer than your daily calorie needs in order to lose a healthy 0.5kg/1lb per week - you may lose more if you're more active too. A structured meal plan can be found below:


It is also important to track the changes to your diet and activity levels to help keep you motivated and to identify where you might be able to improve further.

Weight diary: https://www.wcrf-uk.org/sites/default/files/weight-diary.pdf

12 week planner: https://www.wcrf-uk.org/sites/default/files/healthy-new-you-planner.pdf

Exercise is an extremely important part of the weight loss process so don’t forget it! It not only helps you to burn more calories, but also helps to increase your muscle mass (especially resistance exercise) and improves your mood. When you incorporate it into your lifestyle regularly, it helps to keep the weight off which is the part that people often struggle with the most. Build up the amount of exercise you do slowly so that it is realistic for you to keep it up and choose something you enjoy. It is also good to incorporate more exercise into your usual daily routine such as getting off the bus earlier to walk or cycling instead of getting the train.

Everyone will slip up now and again and it is okay to have a little treat now again. Remember to reward yourself when you do reach your target and then make another one. If you do slip up, accept it and get back on track again. No one is perfect all of the time!