AbstractBackgroundThis study measures the burden of chronic diseases associated with being underweight.MethodsUnderweight prevalence in the community was obtained from national survey data, together with hospital use rates for malnourished and non‐malnourished persons for diagnoses associated with underweight. Meta‐analyses of published literature calculated the following disease‐specific relative risks: incidence of underweight‐associated disease (UAD), mortality from UAD, and all‐cause and disease‐specific mortality after hospitalization in underweight persons. This enabled the calculation of hospital days, deaths, and disability‐adjusted life years (DALYs) attributable to underweight deconstructed into UAD and disease‐associated underweight (DAU). Cost estimates were based on general hospitalization costs adjusted by estimates of pharmaceutical and other direct care costs.ResultsWe found 60,401 (95% confidence interval [CI]: 58,257–63,095) general hospital days, 558 (95% CI: 219–879) deaths, 5258 (95% CI: 2174–8382) potential years of life lost, and 3390 lost DALYs (95% CI: 1511–5333) were attributable to underweight annually in Israeli adults aged ≥18 years. Annually, direct health costs amounted to $145.6 million (95% CI: $141.9–$150.5 million), with general hospital days accounting for $53.4 million, pharmaceuticals $18.2 million, and other direct healthcare costs $73.9 million. Musculoskeletal disorders accounted for nearly half of these costs with coronary heart disease, chronic obstructive pulmonary disease, and stroke accounting for 15.4%, 10.3%, and 9.3%, respectively.ConclusionsUnderweight imposes a considerable health burden in terms of deaths, health service use, and resource costs in Israel. Identification of cost‐effective interventions to reduce this burden, not only among hospitalized patients, but also among persons living in the community, is essential.