The present study used a sample of 167 women ranging from ages 24 to 66 years, attending the radiology department of the Thika level 5 hospital for breast cancer screening revealed that fat intake, fruits and vegetables, weight, physical activity, alcohol consumption, passive tobacco smoking, breastfeeding and hormonal contraceptive use were significant for breast cancer development. Multiple binary logistic regression indicated that women with BMI greater than 28 had a 53.43- fold risk of testing positive for breast cancer (13.2%, p-value 0.00) compared to those with BMI below 22 while those with BMI range from 22 to 27.9 showed 6.07 - fold risk (9.6%, p value < 0.05) of testing positive for breast cancer compared to those with BMI below 22. Those women in the study who had breastfed for between 2 to 4 years had a 0.17- fold risk (5.4%, p-value = 0.001) and women who had breastfed for more than 4 years had a 0.05 -fold risk (3.6%, p-value = 0.00) of testing positive for breast cancer compared to those who had breastfed for less than 2 years. This suggests a protection from breast cancer for those women who breast fed for 2 years and above. Equally, women who spent 3-5 hours engaging in any physical activity had 0.02 (95% CI:0.02 (0.004-0.153) lower odds of testing positive for breast cancer compared to those who spent 1-3 hours daily engaged in any physical activity. Women who passively smoked for more than 3 hours daily had a 15.66- fold risk (95% CI: (4.807-50.983) of testing positive for breast cancer compared to those who did not passively smoke. The results from this study strongly suggest that lifestyle behavior is one of the main predisposing factors to developing aggressive forms of breast cancer.