Cancer represents a significant challenge for humankind, as early diagnosis and treatment are difficult to achieve. To systemically investigate the effect of sex, body mass index (BMI) and age on cancer incidence and prognosis, the data from 14,504 cases of cancer were downloaded from The Cancer Genome Atlas (TCGA). BMI was used to categorize each person as underweight, normal weight, overweight or obese. Two‑ and five‑year survival rates were applied to estimate the prognosis for each cancer type. All data were statistically analyzed. We identified that males were more susceptible to lung, liver and skin cancer when compared with females, whereas females were more susceptible to thyroid, breast and adrenal cortex cancer. High BMI (>25) was positively associated with the occurrence of cancer, although patients with high BMI at the time of initial diagnosis had higher two/five‑year survival rates. The survival rates for cancer were positively correlated with the age at initial pathologic diagnosis. Some types of cancer were associated with particularly young ages of onset, including adrenocortical carcinoma, cervical and endocervical cancers, brain lower grade glioma, pheochromocytoma and paraganglioma, testicular germ cell tumors and thyroid carcinoma. Hence, the early diagnosis and prognosis for these cancers need to be improved. In conclusion, sex, BMI and age are associated with the incidence and survival rates for cancers. These results could be used to supplement precision and personalized medicine.