Methods of weight treatment in animals are presented including: stimulating a retinal ganglia of the animal by an exposure to a narrow spectrum light. In some embodiments, the stimulating the retinal ganglia of the animal is associated with a stimulation of melanopsin. In some embodiments, the stimulation of melanopsin is associated with a inhibition of melatonin secretion. In some embodiments, inhibition of melatonin secretion is associated with a stimulation of leptin secretion. In some embodiments, the stimulation of leptin secretion is associated with a decrease in appetite in the animal. In some embodiments, the exposure to the narrow spectrum light is associated with a weight loss in the animal. In some embodiments, the narrow spectrum light is in a spectrum range of approximately 435 to 520 nanometers.
