Does sitting a lot increase my risk of cancer, even if I exercise?
Sitting a lot increases your risk of certain cancers, even if you exercise. In addition to moving regularly, try to reduce your sitting time itself, because the two only partially compensate for each other.
Sitting a lot increases your risk of certain cancers, even if you exercise regularly. This has now been confirmed in several large analyses. The extra risk is not enormous, but it is measurable: roughly 7 to 29% higher risk depending on the type of cancer, and approximately 13% higher risk of cancer in general. Your chance of dying from cancer is about 18% higher if you spend a lot of time sitting.
The cancer types for which this association is most clearly apparent are uterine, ovarian, colon, breast, prostate and rectal cancer. For most of these, the evidence is considered 'suggestive': the association has been found repeatedly, but definitive causal proof in humans does not yet exist for all types. A genetic study on breast cancer provides stronger indications that the relationship is genuinely causal, not merely coincidental.
Exercise helps, but does not fully solve the problem. People who exercise a lot and sit a lot have a lower risk than someone who sits and does not exercise. Yet the risk is still higher than for someone who sits little. In other words: an hour of cycling in the morning does not cancel out the eight hours at your desk that follow. Sitting less and moving more are therefore complementary, not interchangeable choices.
Exercise, incidentally, has a well-proven protective effect on six types of cancer: bladder, breast, colon, uterine, oesophageal and stomach cancer. But those who exercise outdoors should pay attention to the sun: outdoor exercise is associated with a higher risk of melanoma, a serious form of skin cancer. Good sun protection is therefore not a minor consideration.
Based on multiple systematic reviews and meta-analyses (PMID 32741068, 31626056, 35612669, 29589226, 25599350). All associations are observational; causal evidence in humans is limited to the Mendelian randomisation study for breast cancer. Risk estimates are adjusted for physical activity.
Does being overweight increase my risk of cancer, and if so, which types?
Excess weight increases your risk of at least 13 types of cancer, including uterine, colorectal, breast and liver cancer. Losing weight reduces that risk, although it remains unclear whether all methods of weight loss are equally effective for immune defence against cancer.
Does exercise lower my risk of cancer?
Regular physical activity is associated with a clearly lower risk of several cancers in large population studies. Alongside that, aim to reduce the number of hours you spend sitting during the day, and use sun protection if you do a lot of outdoor sport.
Does eating a lot of sugar increase my risk of cancer?
Drinking large amounts of sugar-sweetened beverages is associated with a noticeably higher risk of certain cancers, particularly early-onset colorectal cancer and liver cancer. The association is observational, but consistent enough to make reducing soft drinks and fruit juice a concrete point of attention.
Does poor sleep increase my risk of cancer?
Poor sleep, and certainly untreated sleep apnoea, is associated with an increased cancer risk, but it has not yet been proven that sleeping poorly causes cancer. Have sleep apnoea checked if you have symptoms, and try to maintain a regular sleep schedule.
Does working at night increase my risk of cancer?
Night work probably increases the risk of breast cancer, and possibly of other types of cancer. If you have been working night shifts for years, it is worthwhile to discuss this with your doctor and to stay alert to population screening programmes.
Does a large belly increase my risk of cancer more than being simply overweight?
A large belly increases the risk of several cancer types more than being simply overweight, especially in men. Having your waist circumference measured is therefore more meaningful than paying attention only to the scales.