High body weight seems protective of bone mass, specifically bone mineral content (BMC) and bone mineral density (BMD), thereby reducing the risk of osteoporosis. Cognitive eating restraint (CER), diet composition, and the satiety hormone, leptin, produced by adipocytes, are associated with body mass and may also influence bone mass. Few studies have examined these relationships. To investigate the relationship between leptin and CER score, 36 premenopausal, healthy weight women, as defined by body mass index (BMI) of 18-25 kg/m², aged 18-25 years were studied. Women were categorized by baseline Eating Inventory questionnaire scores into either the high CER group (score > 9, n = 20) or low CER group (score < 9, n = 16). Serum leptin concentration was significantly lower in the low CER group versus high CER group at baseline. A positive relationship between serum leptin concentration and body fat mass and body fat % in normal weight women despite differences in CER scores was observed. In a separate study, overweight and obese women, (BMI > 25 to < 43 kg/m²), aged 32-45 years, were randomly assigned to either a low-carbohydrate, high-protein (LCHP) or low-fat, high-carbohydrate (LFHC) diet for 12 weeks. Serum leptin concentration was significantly greater in the LCHP versus the LFHC diet group at 12 weeks (p < 0.05). Over time, significant decreases in serum leptin concentration, BMI, body weight, total lean mass, total fat mass, and body fat % were observed in both diet groups. Serum leptin concentration was positively associated with body weight, fat mass, and body fat % regardless of diet consumed. Both studies are novel in their respective populations and show no direct link between leptin and bone mass when considered in the context of CER or diet composition.