Previous systematic reviews on the relation between overweight or obesity and breakfast focused on the frequency of consumption and only partially accounted for breakfast nutritional profiles. Given the central role of these factors, we conducted a systematic review of the literature on this putative relation, with a specific focus on breakfast energy intake and/or breakfast composition. Among the 814 articles identified from the literature search in PubMed, 19, mostly cross-sectional, studies met the inclusion criteria (i.e., studies providing a quantitative estimate of the relation between any measure of weight, overweight, and obesity and breakfast energy intake or breakfast macronutrient composition). We excluded studies in subjects with acquired metabolic disorders, such as diabetes or impaired glucose tolerance. Of the 16 studies that evaluated the amount of energy intake at breakfast, 4 found that a lower energy intake at breakfast was significantly associated with obesity in children, adolescents, and adults, whereas 2 partially overlapping studies found that a higher energy intake was significantly associated with a higher body mass index in children. Of the 8 studies investigating breakfast composition, 3 suggested that a breakfast characterized by a higher amount of carbohydrates and a lower amount of fat is significantly related to normal weight in adults, whereas the others reported mixed results. In conclusion, there is some evidence that a lower energy intake at breakfast is related to obesity, although the studies are few and heterogeneous. Studies on the nutrient composition of breakfast have shown inconsistent results.