Some of the universal characteristics of pre-agricultural hominin diets are strikingly different from the modern human diet. Hominin dietary choices were limited to wild plant and wild animal foods, while the modern diet includes more than 70 % of energy consumed from refined sugars, refined vegetable oils, and highly processed cereals and dairy products. The modern diet, with higher intake of fat has also resulted in a higher ratio of omega-6 (n-6) to omega-3 (n-3) polyunsaturated fatty acids (PUFA), contributing to low-grade chronic inflammation (LGCI) and thus promoting the development of many chronic diseases, including obesity and osteoporosis. In this review, we describe the changes in modern diet, focusing on the kind and amount of consumed fat; explain the shortcomings of the modern diet with regard to inflammatory processes; and delineate the reciprocity between adiposity and inflammatory processes, with inflammation being a common link between obesity and osteoporosis. We present the evidence that overconsumption of n-6 PUFA coupled with under-consumption of n-3 PUFA results in LGCI and, along with the increased presence of reactive oxygen species, leads to a shift in mesenchymal stem cells (precursors for both osteoblasts and adipocytes) lineage commitment toward increased adipogenesis and suppressed osteoblastogenesis. In turn, high n-6 to n-3 PUFA ratios in the modern diet, coupled with increased synthesis of pro-inflammatory cytokines due to adiposity, propagate obesity and osteoporosis by increasing or maintaining LGCI. Pojedina univerzalna svojstva prehrane hominina prije pojave poljodjelstva izrazito se razlikuju od suvremene prehrane. Prehrambene navike hominina vjerojatno su bile ograničene na plodove divljeg bilja i lovinu; više od 70 % moderne prehrane odnosi se na konzumaciju rafiniranih šećera, biljnih ulja, žitarica i mliječnih prerađevina. Moderna je prehrana s višim unosom masti također dovela do nepovoljnijeg omjera omega-6 i omega-3 višestruko nezasićenih masnih kiselina (engl. krat. PUFA), koji pridonosi održavanju kronične upale niskoga stupnja, a time i nastanku mnogih kroničnih bolesti, uključujući pretilost i osteoporozu. U ovom se preglednom članku opisuju promjene uslijed modernog načina prehrane, s posebnim osvrtom na vrste i količine konzumirane masti. Također se objašnjavaju nedostatci moderne prehrane s obzirom na upalne procese te međusobna povezanost između pretilosti i upalnih procesa, koji su usto i poveznica između pretilosti i osteoporoze. U članku se iznose saznanja o tome da pretjerana konzumacija omega-6 masnih kiselina uz nedostatnu konzumaciju omega-3 masnih kiselina dovodi do kronične upale niskoga stupnja i povišenih vrijednosti reaktivnih kisikovih čestica (ROS), a time i do pomaka u mezenhimskih matičnih stanica (prekursora osteoblasta i adipocita) prema povećanoj adipogenezi i smanjenoj osteoblastogenezi. Uz povećanu sintezu upalnih citokina zbog pretilosti, moderna prehrana s nepovoljnim omjerom omega-6 i omega-3 kiselina u korist prvih nastavlja poticati pretilost i osteoporozu jer održava i pogoršava kroničnu upalu.