How Obesity Can Cause Cancer Obesity is the second-biggest preventable cause of cancer, after smoking cigarettes. A staggering 22,800 cancer cases in the UK are caused by excess body weight. New research from Trinity College, Dublin has now revealed a correlation between obesity and cancer. Cancer-fighting cells get clogged with fat and stop working. Researchers are hoping to find a treatment that could restore the cells' fighting abilities. This study reveals how fat molecules prevent immune cells from properly positioning their tumor-killing machinery, and provides new avenues to investigate treatments. To help prevent cancer, physicians suggest keeping a healthy body weight, avoiding smoking, minimizing alcohol and reducing risk of sunburn.