To help ensure an unbiased review, we conducted a systematic search of PubMed using cross-sections of key words relating to paternity (‘paternal’, ‘father*’, ‘intergenerational’, ‘transgenerational’), and obesity (‘obes*’, ‘overweight’, ‘body weight’, ‘BMI’, ‘body mass index’, ‘fat’, ‘adiposity’, ‘adipose’) or type 2 diabetes (‘diabet*’, ‘T2D’, ‘metabol*’, ‘glucose’, ‘insulin’). This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.