Weight gain as adult increases cancer risk by up to five times, research shows
(www.theguardian.com)
There is a mountain of evidence that shows 13 different cancers are directly caused by obesity. 8 more are suspected to be caused through excess weight.
When something is 500% more likely when a biological factor is introduced, it’s 100% correlation with strong possibility to be causation. So strong that there is no point asking that question unless you are asking it in bad faith.