There is scientific evidence that the endocannabinoid system (ECS) plays an important part in how the body regulates energy, carbohydrate and fat metabolism. Endocannbinoids and some naturally occurring phytocannbinoids in cannabis activate cannabinoid receptors CB1 and CB2 receptors. The CB1 receptor is believed to be responsible for the hunger centers of the brain that affects appetite and energy intake. CB1 receptors also exist in the peripheral tissues outside the brain which include the adipose (fat), liver, gut, pancreas and skeletal muscle.
CBD lowers insulin resistance, therefore it's less likely to gain weight for people who over eat. If your ECS is not regulating the body properly, CBD can bring the body into homeostasis, or balance.
Després JP. The endocannabinoid system: a new target for the regulation of energy balance and metabolism. Crit Pathw Cardiol. 2007 Jun;6(2):46-50.