For women diagnosed with breast cancer, maintaining a satisfactory weight is one of the most important life goals. Most studies over the past decades have considered patient overweight or obesity at initial diagnosis as a poor prognostic factor, perhaps also associated with poor lymph node metastasis and various poor prognoses (e.g., contralateral lesions, recurrence, coexisting disease, and/or disease-specific or overall mortality, and treatment effects such as chronic lymphedema). Considering that overweight and obesity are well established risk factors for poor prognosis, and that many women are overweight at the time of breast cancer diagnosis, weight control is an important thing to consider for breast cancer patients. In addition to this, many women have been reported to gain weight after a breast cancer diagnosis, and an analysis of non-smoking breast cancer patients in the Nurses Health Study confirms these findings. Researchers found that women who gained 0.5 to 2 units of BMI had a 40 percent higher recurrence rate, and women who gained more than 2 units of BMI had a 53 percent higher recurrence rate compared to patients who gained no more than 0.5 units of BMI. This study showed that the prognosis of female patients with weight loss was not significantly worse. However, other recent studies have not found evidence of a prognostic impact of weight gain. Although unexplained weight loss is considered a sure sign of disease recurrence and should be closely monitored, there is a fundamental difference between intentional weight control or weight loss and unexplained or disease-induced weight loss. Indeed, a growing body of data shows that being overweight or obese affects not only tumor-specific regression, but also overall health status and quality of life, making weight control a priority standard of care for overweight women with early-stage breast cancer. Studies from the previous decade as well as recent studies have shown that weight gain in women with breast cancer after neoadjuvant chemotherapy or hormonal therapy appears to be due to an increase in adipose tissue, while there is no change in non-adipose tissue. This unpleasant change in body composition suggests that interventions should not be limited to weight control, but should also aim to preserve or rebuild the body’s muscle tissue. Moderate physical activity (especially resistance training) during or after treatment can help patients maintain muscle and avoid excessive fat accumulation. Even if the ideal weight is not achieved, a weight loss of 5% to 10% over 6 to 12 months in the general population is sufficient to reduce levels of factors associated with chronic disease risk, such as elevated blood lipid levels, fasting insulin levels, etc. At the same time, a recent review of the scientific literature shows that deliberate weight control can promote benign changes in breast cancer – related biomarkers such as estrogen, sex hormone-binding globulin, and inflammatory markers. There are substantial studies on physical activity in breast cancer patients and several systematic reviews that focus on exploring its individualized role. In a meta-analysis of 14 randomized controlled trials that included 717 breast cancer patients, physical activity was shown to cause significant improvements in quality of life, body function, and peak oxygen consumption, as well as reductions in fatigue symptoms. Another meta-analysis that included six prospective cohort studies of 12,000 breast cancer patients showed that post-diagnosis physical activity was associated with a 24% reduction in recurrence, a 34% reduction in mortality, and a 41% reduction in all-factor mortality. Although the results are encouraging, further randomized controlled studies are necessary to examine the benefit of exercise in stopping cancer recurrence and improving survival in women with breast cancer. Despite the increasing use of sentinel lymph node dissection, chronic lymphedema remains a major concern for breast cancer patients. However, aerobic exercise and resistance training appear to be safe and effective in reducing the incidence of chronic lymphedema in those at risk and may improve the condition in patients with pre-existing symptoms. Progressive resistance training needs to be performed under the guidance of a training therapist and appropriate tight-fitting clothing is recommended. In addition, because obesity is a major risk factor for chronic lymphedema, weight loss is still recommended for overweight or obese patients. Researchers have worked together to evaluate the effects of different recipe components on cancer-specific regression, as well as overall health status. An observational study found that dietary patterns had a significant impact on overall survival in breast cancer patients, with patients who ate a predominantly Western diet having poorer overall survival rates and those who ate a large amount of vegetables and fruits and whole grains daily having better overall survival rates. However, none of the diets were specifically associated with breast cancer recurrence. The biggest difference between the two diets mentioned above is the fat content; however, to date, there is no valid evidence to support the association of dietary fat intake with breast cancer recurrence risk and survival, especially since total energy intake values and obesity levels also influence these results. Two large clinical trials examined whether changes in dietary composition could reduce the risk of recurrence and increase overall survival in breast cancer patients. The researchers found a 24% reduction in recurrence rates in the WINS low-fat dietary intervention group, which showed continuous significance, and weight loss in this group, so the benefit may also be due to weight loss rather than a reduction in fat intake. In the WHEL study, the dietary intervention also included a reduction in fat intake among its goals, but the dietary intervention (which was not associated with weight loss) was not observed to have the desired effect. The association between increased vegetable consumption and reduced risk of breast cancer is not clear, and there is little evidence to support that increased fruit consumption reduces recurrence rates or prolongs survival. However, the strongest intervention was an increase in vegetable and fruit intake, which was very high in this group, with an average of more than 7 servings per day, and no difference in relapse-free survival was found between the two cohorts in this study. The WHEL study intervention did improve the prognosis of women without hot flashes, suggesting that there may be a survival benefit for women with higher circulating estrogen levels. On the other hand, the researchers found that longitudinal exposure to carotenoids (biomarkers of dark squash intake) was associated with longer recurrence-free survival, suggesting that prediagnostic intake of vegetables and fruits may help improve the prognosis of breast cancer patients. Vegetables dilute the total energy density of the diet, and they and fiber may improve satiety. Data from the Nurses Health Study of breast cancer patient subjects suggest that consumers who consume large amounts of fruits, vegetables, whole grains and less healthy diets containing sugar, refined grains, and meat may benefit from significantly lower recurrence or cancer-specific mortality rates, as well as lower mortality from other diseases, such as heart disease, compared to typical Western diet consumers. Soy foods and flaxseed foods are rich in phytoestrogens, bioactive substances called isoflavones that exhibit both anti-estrogenic and estrogen-like properties. High circulating estrogen levels are a recognized risk factor for breast cancer recurrence. Soy isoflavones have been shown to promote the growth of breast cancer cells in vitro and mammary tumor cells in experimental animals, so there is a concern that consuming soy may have a negative impact on the prognosis of women with breast cancer. However, large epidemiological studies in recent years have found no adverse effects on breast cancer recurrence or overall survival with soy foods alone or in combination with tamoxifen, and on the contrary, these foods may have synergistic anti-cancer effects with tamoxifen. Two of these studies focused on U.S. patient samples and included isoflavone factors in their data collection and analysis. The available evidence suggests that consumption of soy-based foods does not adversely affect the risk of recurrence or survival. Supplemental application of isoflavones is uncommon in the populations of recent cohort studies, so the evidence related to this supplemental effect is even more limited. Alcohol intake is thought to be associated with an increased risk of primary breast cancer; however, there is a mixed association in the cancer patient population, with one paper showing a protective effect of alcohol intake, another showing that alcohol consumption can cause ovarian cancer, another reporting that alcohol consumption is associated with contralateral disease, recurrence, and death, and yet another reporting that small or moderate amounts of alcohol neither have a protective nor an increasing effect on breast cancer risk There is also literature that says that small or moderate amounts of alcohol have neither a protective nor an increasing effect on breast cancer risk. The conflicting opinions on the association between alcohol and overall survival may be partly due to the fact that alcohol intake reduces the risk of cardiovascular disease, which is a common complication in breast cancer patients, contrary to the effect of obesity. Theoretically, alcohol intake affects the risk of second primary breast cancer, and indeed all breast cancer patients are at great risk of developing second primary cancer. Alcohol is not considered a common correlate because of the coexistence of risk and benefit. For the general population, the evidence is clear and consistent that moderate alcohol consumption (1-2 drinks per day) reduces the risk of cardiovascular disease. For breast cancer patients, the effects of moderate alcoholic beverage consumption are complex and require consideration of both the risk of recurrence and second primary breast cancer and the cardiovascular disease benefit. Recommendations regarding nutrition and physical activity are critical for breast cancer patients to reduce second primary breast cancer and heart disease. The diet needs to emphasize vegetables and fruits, be low in saturated fat, and include adequate dietary fiber. Most importantly, breast cancer patients should maintain a healthy weight through a balanced diet and increased exercise. In addition, regular physical activity should be maintained regardless of weight level.