Assessing the evidence for health benefits of low-level weight loss: a systematic review.

Individuals with excess weight are at a higher risk for various physical and mental health conditions. Interventions targeting weight loss can improve health, with modest weight loss of five to ten percent of body weight often considered clinically meaningful for enhancing health outcomes. However, the benefits of achieving low-level weight loss ( < 5% body weight) are poorly understood. We aimed to systematically review relevant literature and synthesise the evidence that assessed the potential health benefits of losing less than five percent body weight. We searched seven academic databases and included studies in any language, from any country, with no time constraints. We included any intervention studies that assessed the impact of less than five percent weight loss on any measured physical or mental health markers or indices. 70 studies from 68 articles were included, with study participants ranging from 14 to 10,742. In total, 137 health markers were assessed, categorised into metabolic markers (n = 42), cardiovascular markers (n = 32), anthropometric measures (n = 19), quality of life indices (n = 10), inflammatory biomarkers (n = 10), renal and hepatic markers (n = 9), psychosocial and behavioural measures (n = 8), pulmonary function (n = 3), total mortality (n = 2), ovulatory function (n = 1), and muscle strength (n = 1). Overall, 60% of studies reported improvements, 37% found no change or mixed results, and 3% observed a worsening of health markers or indices. Based on the available data, 87% of participants (n = 15,839) in the studies reported improvements in health markers or indices as a result of low-level weight loss. Our findings suggest that low-level weight loss can lead to various health benefits and challenges the conventional threshold for effective weight loss.Preregistration The review protocol was pre-registered with PROSPERO (CRD42023406342).