Does diet and exercise really get you that far against cancer though? My sense is that it helps but only a fraction of the amount that it does against cardiovascular disease, is that right?
I doubt any disease will grant you more energy than what you've eaten nor conditions that substantially improve the bodies efficiency. It's important to remember that exercise alone won't burn off that many calories. It's diet that is primarily responsible for that
It’s an argument that is as old as the hills and relies on the assumption that the body functions like a simple furnace, which of course is false.
Metabolic rates vary significantly, and rates of absorption of nutrients and consumption of energy vary a lot as a result of factors such as inflammation and endocrine function.
Calories in/calories out may still ultimately be true when you boil it down far enough, but the factors influencing and intervening in those processes are vastly complex and strongly affected by diseases and dysfunctions that are very common.
Thyroid disorder (which can include cancer or a precursor condition) is probably the most common/known, but just one of many.
The short answer is yes, they can make a meaningful difference to risk, but as ever with cancer, the long answer is that there are a lot of risk factors and they aren't the same from one type of cancer to another. I'm not a medical expert, just someone who's supported cancer research for a long time and has a lay person's understanding of the issues, so I'll leave it to more knowledgeable people to comment any further.
>Nearly all of the evidence linking physical activity to cancer risk comes from observational studies, in which individuals report on their physical activity and are followed for years for diagnoses of cancer. Data from observational studies can give researchers clues about the relationship between physical activity and cancer risk, but such studies cannot definitively establish that being physically inactive causes cancer (or that being physically active protects against cancer). That is because people who are not physically active may differ from active people in ways other than their level of physical activity. These other differences, rather than the differences in physical activity, could explain their different cancer risk. For example, if someone does not feel well, they may not exercise much, and sometimes people do not feel well because they have undiagnosed cancer.
I would really like to see some proper studies done. Unfortunately, seeing friends and otherwise healthy, physically active people passing away from cancer at a relatively young age does not inspire hope at the moment.
Not that I'm disagreeing with the limitations of observational studies, but it's not quite that simple. Cancer Research UK describes being overweight or obese as the second biggest preventable cause of cancer (after smoking):
In particular, there appears to be a causal link between being fat and an increased risk of some cancers via several identified mechanisms, though of course this whole area is a subject of ongoing research.
Given the well-understood links between a healthy diet, getting enough exercise, and maintaining a healthy body composition, it's important to pay attention to both diet and exercise in order to minimise cancer risk, even taking into account the other effects.
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