Do dogs lose weight when they are on heat or pregnant?

 It is possible for dogs to lose weight while they are in heat or pregnant, but it is not a universal phenomenon. The most important factor in a dog's weight is the balance between calorie intake and energy expenditure. If a dog's caloric intake remains constant but their energy expenditure increases due to hormonal changes or increased physical activity, they may lose weight. On the other hand, if a dog's appetite increases due to hormonal changes or the demands of pregnancy, they may gain weight. It is important to monitor your dog's weight and consult with a veterinarian if you have any concerns about changes in their weight.