Obese men had a twofold increased risk of colorectal cancer compared to men who are not obese (SRR = 2.09; 95% CI = 1.23-3.55, I2 = 33%). For women, there was no discernible rise in risk from obesity. For those with an MLH1 mutation, the probability of developing colorectal cancer due to obesity increased by 49% (SRR = 1.49; 95% CI = 1.11-1.99, I2 = 0%). Here, MLH1 is linked to obesity due to melanocortin 4 receptor deficiency.