As stated above, fish oil offers various health benefits and this includes weight loss. So instead of gaining weight, it can help reduce hunger and appetite as well as boost the metabolism and the effects of exercise -- leading you to lose body fats. This is why many people include a fish oil supplement in their diet plans. However, this doesn't apply to everyone. The effects still vary depending on one's current health status and diet routine. So, it's important to consult with a dietician or health specialist before you make any decisions.