You'll want to be a bit more careful in how you cite that to people. That's the CDC, not the American Health Organization.
Also, it doesn't say that 40% of cancer is due to diet. It says that 40% of cancer diagnoses are types of cancer that are associated with being overweight or obese. This does not mean that 40% of cancers are due to diet for several reasons.
Being overweight or obese is not always due to diet. You could become overweight for other reasons and still suffer many of the negative health consequences.
Correlation is not causation. Just because a cancer is associated with being overweight doesn't necessarily mean that being overweight causes the cancer. Perhaps some cancers cause you to become overweight. Perhaps there are some third factors that cause both. Maybe one of those factors is diet for some cancers but not others.
Having a cancer that is caused by with being overweight or obese doesn't mean that it was a cause or the cause of your particular cancer. Just as there are nonsmokers with lung cancer, there will be a lot of skinny people in that 40%.
Also, it doesn't say that 40% of cancer is due to diet. It says that 40% of cancer diagnoses are types of cancer that are associated with being overweight or obese. This does not mean that 40% of cancers are due to diet for several reasons.
Being overweight or obese is not always due to diet. You could become overweight for other reasons and still suffer many of the negative health consequences.
Correlation is not causation. Just because a cancer is associated with being overweight doesn't necessarily mean that being overweight causes the cancer. Perhaps some cancers cause you to become overweight. Perhaps there are some third factors that cause both. Maybe one of those factors is diet for some cancers but not others.
Having a cancer that is caused by with being overweight or obese doesn't mean that it was a cause or the cause of your particular cancer. Just as there are nonsmokers with lung cancer, there will be a lot of skinny people in that 40%.