Maintaining a healthy weight 

Maintaining the correct weight for your height is a key part of reducing your risk of breast cancer. There are many reasons why you might put on weight. Inherited genes, lifestyle, and what you eat can all play a part.

If you’re unsure whether you are a healthy weight you can find out by calculating your Body Mass Index. 

How is weight linked with breast cancer risk?  

Being overweight or obese can affect our bodies in many different ways. It can help to promote the growth of several cancers, including breast cancer. Obesity has complex effects on the body’s cells. It can affect their ability to grow and repair, your immune system, and, importantly for breast cancer risk, your hormone system.  

Fat (adipose) cells can generate the sex hormone oestrogen. This is especially relevant for postmenopausal women as fat becomes the main source of oestrogen after menopause. Having higher oestrogen levels postmenopause can increase breast cancer risk.

A large UK study identified around a 30% higher risk of breast cancer in postmenopausal women who were obese compared to those of a healthy weight. In addition to oestrogen, fat cells can release a hormone called leptin. Studies have shown that higher leptin levels can increase the risk of developing breast cancer.  

Weight gain and obesity can lead to long-term (chronic) inflammation within our bodies. This means that the immune system can be active when it shouldn’t be. Obesity-related inflammation can also encourage insulin resistance, which means that there may be too much sugar in the blood, leading to several health implications.    

Variety and portion sizes 

Keeping a healthy weight can sometimes be easier said than done but try only to eat as much as you need – so you don’t gain excess weight. The amount you eat is just as important as what you eat. 

Your age, sex, height, and activity levels all play a part in determining what portion size you should be eating.  Judging the portion size you should eat is key, and your hand can serve as a simple measuring aid. Here is our guide to portion sizing: 

Fruit and vegetables  

• 5 or more portions per day (at least three portions of vegetables, two portions of fruit) 
• One portion of fruit can be classed as one whole fruit, such as an apple, a banana, a pear, or an orange. 
• One portion of vegetables can be classed as two large broccoli spears (or eight small florets), or four heaped serving spoons of cooked kale, spinach, spring greens, or green beans. 

Starchy carbohydrates 

• 3-4 portions per day 
• One portion (lighter meals) can be classed as six small cooked new potatoes, about one and a half handfuls of porridge (dry weight); two slices of medium-sliced wholemeal bread. 
• One portion (main meals) can be classed as two handfuls of plain, dried wholemeal pasta; two handfuls of wholemeal, dried rice; one large wholemeal bread roll. 

Protein (beans, pulses, fish, eggs, meat, and others) 

• 2-3 portions per day 
• One portion (lighter meals) can be classed as two eggs, or 80g of tofu, or about six tablespoons of lentils, beans, or other pulses. 
• One portion (main meal) can be classed as about half the size of your hand of raw salmon fillet or raw mackerel fi­llet. 

Dairy and alternatives 

• 2-3 portions per day 
• One portion can be classed as one glass of milk (semi-skimmed) or unsweetened plant-based milk, or about 4 tablespoons of plain yoghurt (low fat), or about three tablespoons of cottage cheese. 

The British Nutrition Foundation’s portion guide is a useful guide.  

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