Breast cancer studies outline what age women should lose weight to slash risk

Women who are overweight in early adulthood may be less likely to develop breast cancer after menopause , research suggests.

Scientists behind the study of 58,000 women in Greater Manchester say the relationship between body mass index (BMI) and breast cancer is "complex" but warn that being overweight generally increases women’s risk.

A separate study of 110,000 women in the Breast Cancer Now Generations Study showed that alcohol intake and piling on weight were a bigger risk factor during women’s 30s and 40s.

Researchers behind the Manchester study suspect lasting changes in the structure of their breast tissue in women who tended to carry more weight at a young age could have a protective effect.

The UK PROCAS study of women aged 46 to 73 showed those who had a higher BMI when they were aged 20 appeared to have a reduced risk of post-menopausal breast cancer. But those with a higher BMI in later adulthood and higher breast density had an increased risk.

Author Prof Andrew Renehan, of Manchester University, said: "These findings do not suggest that gaining weight is protective. What they offer is further insight into how breast tissue and consequent breast cancer risk may be shaped across a woman's lifetime.

"Maintaining a healthy weight remains important, because excess weight in later adulthood is linked to a higher risk of breast cancer and many other serious diseases. But this study adds to growing evidence that exposures during early life can have lasting effects on health decades later."

Experts already know that around a quarter of breast cancers could be prevented through healthy lifestyle changes, such as taking more exercise, maintaining a healthy weight and drinking less alcohol.

Experts say women in their 30s and 40s should be warned about the risks of alcohol and excess fat to help cut their risk of breast cancer.

The Generations Study found that lifestyle factors known to increase the chances of developing cancer actually differ depending on which life stage women are at.

Author Professor Marc Gunter, chairman in cancer epidemiology at Imperial College London, said: "Our study has shown that adolescence and early adulthood may be a particularly important time to encourage physical activity and help prevent rapid weight gain.

"Early to mid-adulthood, from around the 30s to 50s, could be a key period for tackling rising body mass index (BMI) and renewed increases in alcohol consumption."

The findings, published in Scientific Reports, showed how major breast cancer risk factors related to lifestyle, such as alcohol consumption, smoking, exercise and weight, change throughout the course of people's lives.

While alcohol consumption, smoking and physical activity peaked in late adolescence, body fat steadily increased throughout adulthood, peaking in the late 60s. Women born between 1960 and 2003 generally had higher BMI trajectories throughout life and their level of smoking and alcohol consumption peaked at younger ages, than women born between 1908 and 1959.