Many people have problems with body weight gain or loss leading to excess weight and obesity or underweight, which lead to higher mortality and morbidity and increased risk for many diseases. In addition, body weight abnormalities may coexist with malnutrition. Garden cress (Lepidium sativum Linn, LS) seeds are widely used in many countries in the Middle East and Asia for their nutritive value and the treatment of many diseases and ailments. This study aimed to determine whether 10% and 15% LS seeds (seeds weight/feed weight) mixed with the diet of rats increase or decrease body weight and weight gain so that users may be able to decide to use them or not according to their needs and weight status. This is the first study to use 15% LS seeds mixed with the diet of rats. The mean weekly body weights and weekly body weight gains were determined in rats consuming ground LS seeds for six weeks. Ground LS seeds mixed with the regular feed were administered to rats at a low dose (LD, 10% LS seeds, 12 rats) and high dose (HD, 15%, 10 rats) and the findings were compared to the control group rats (12 rats) that were not given the seeds. The findings showed that the addition of LS seeds to the diet of rats led to increased mean body weights and body weight gains for the first three weeks with the effects being higher for the HD group. Subsequently, the increases started to diminish becoming not different from the control. Thus, LS seeds may be ingested for weight gain for three weeks, while if they are taken for any medicinal purposes any gain in weight will diminish after around three weeks.