A naturally lean, light-framed mover sitting right in the healthy zone for body fat, but with total weight and BMI below the typical healthy range — and what fat he does carry sits mostly around the midsection. His body's natural advantage is staying lean (it resists fat gain, but sheds mass just as easily), so his single highest-impact move is building healthy lean mass — the low BMI and the high waist-to-hip ratio are the key health flags — through progressive strength training, a slightly higher energy intake, and protein- and fibre-forward whole foods, all while keeping everyday activity steady to protect the balance he already has.