This study reviews the effects of low-protein diets supplemented with essential amino acids (LPS diets) on egg production performance, nitrogen excretion, and environmental gas emissions from layer-manure composting for laying hens across the entire laying period, focusing mainly on our previous studies. Compared to hens fed control diets (Cont diets), hens fed LPS diets showed no significant differences in egg-laying rates or egg weights across the laying period. Furthermore, LPS diets decreased the nitrogen intake and nitrogen excretion of laying hens as well as the emissions of greenhouse gases and ammonia from layer-manure composting compared to Cont diets throughout the laying period. Integrating the results of the studies and calculating the effects across the entire laying period based on the experimental conditions in the studies (White Leghorn hens and manure composting without forced aeration), we found that feeding LPS diets with a 2% lower crude protein content to laying hens decreased nitrogen influx to Japan and nitrogen load in Japan associated with egg production by 11.7% and 19.7%, respectively, and emissions of greenhouse gases and ammonia from layer manure composting by 23.8% and 29.2%, respectively, compared to feeding Cont diets. Therefore, feeding LPS diets to laying hens throughout the laying period was suggested to reduce the nitrogen load and environmental gas emissions from manure composting without affecting egg production performance.