Modifying the risk associated with obesity

Obesity is one of the few risk factors for breast cancer that can be modified throughout life. Positive lifestyle choices that control obesity, such as adhering to a healthy diet and regular physical activity, can have a significant positive impact on the incidence and prognosis of breast cancer ^[53]. It has been suggested that reducing obesity would decrease the incidence of breast cancer by one-tenth in Europe, with a consequent reduction in mortality rates ^[54]. The Cancer Prevention Study II concluded that up to 18 000 deaths in US women aged >50 years could be avoided if women maintained a BMI of <25 throughout their adult life ^[9].

In addition, some investigators have argued that increasing physical activity and decreasing body fat are reasonable interventions to decrease insulin and leptin levels, which may improve the prognosis of breast cancer ^[55]. Follow-up data from several long-term cohort studies support the hypothesis that lifestyle factors such as diet and physical activity may improve the prognosis of women diagnosed with breast cancer ^[56]. However, another factor to consider is that weight gain is also a common side effect in women receiving adjuvant chemotherapy, which may have negative long-term implications for survival ^[57,58].

Conclusion

A consistent, independent, and positive association has been found between obesity and the development of breast cancer in postmenopausal women, and a preponderance of the literature supports an association between obesity and a poor breast cancer prognosis in both pre- and postmenopausal women.

In the future, it is feared that the effect of the increasing prevalence of obesity (especially in the western world) will manifest as an increased incidence of breast cancer among postmenopausal women, and that this rising rate of obesity may limit the reduction in breast cancer-related mortality that may otherwise have resulted from improvements in the detection and treatment of breast cancer. Obesity, regardless of how it is assessed, adversely affects the development and prognosis of breast cancer.

There are ample data to suggest that obese and physically inactive breast cancer patients have a poorer survival rate compared with lighter weight and more active women.

Despite complex and at times controversial data, enough evidence is presently available to suggest that weight management should be a part of the strategy to prevent breast cancer development, recurrence, and death. Curbing the twin epidemics of obesity and breast cancer demands not only changes in diet and lifestyle at an individual level, but also changes in the political, physical, and social environment. Weight management, with diet and lifestyle advice or interventions, should be an integral part of the follow-up of breast cancer patients.