A large analysis reported that gaining weight in adulthood is associated with a higher risk of developing cancer, with no “safe” period identified for weight gain. The findings come from researchers who examined data on more than 600,000 men and women. Participants were weighed multiple times across decades, allowing scientists to track changes in body weight over time rather than relying on a single measurement. The study reports that cancer risk increases alongside adult weight gain, and that the magnitude of risk can be substantial for people who put on more weight. One account of the results states that the risk could rise up to fivefold, though the estimate depends on how weight change is categorized and compared against lower-gain groups. The study also emphasizes that body weight trajectories matter, not just baseline body size. The sources present the work as a warning that sustained or significant weight gain in middle age and later is linked to worse cancer outcomes, while not suggesting that weight gain at any specific adult age eliminates risk.