Weight loss simply refers to reduction of body mass, whether it is by reducing fat or water content and whether it is intentional or not.Sometimes you want to lose weight, and sometimes a medical condition can cause weight loss. Unintentional weight loss is always a cause for concern and warrants a visit to your physician.When you lose weight, you can lose fat, muscle, or water - or a combination of these. If you are overweight, diet and exercise can help you to reduce your overall weight and body mass.Unintentional Weight-LossIf you find that you start losing weight without trying, there could be a number of different factors at work. Many medical conditions can cause this to occur.For example, if you have Type I diabetes and it is not managed well, you can begin to lose weight without trying. This is because your body begins burning fat and muscle for energy since it cannot access the glucose from the food you are eating. This is a serious condition that needs to be addressed by a physician.Other conditions that can cause unintentional loss of weight include altered metabolism due to HIV infection, hormonal imbalances like overactive thyroid gland, and even some forms of cancers.If you start to lose weight without trying, how do you know when to see a doctor? A good rule of thumb is to be concerned if you lose five percent of your body weight in a month or ten percent over six months.Intentional Weight LossOf course, the more familiar type of weight loss results from deliberately attempting to lose weight due to obesity or generally wanting to be healthier. This is sometimes referred to as therapeutic weight loss, and is usually used to improve the health or change the appearance.If you have any medical conditions that are adversely affected by being overweight, intentional weight loss is a good goal. These illnesses can include things like diabetes, heart disease, high blood pressure and cholesterol, and arthritis.Perhaps you just want to be able to move a little easier or have more energy. Intentional weight loss can help you to achieve these goals also. Eating a little less and moving a little more can take off those few excess pounds that are slowing you down. You may have an easier time participating in your "weekend athlete" activities if you lighten you load a bit.One important point to note is that crash dieting can be dangerous and should be avoided or only undertaken under the supervision of a physician. The body can have serious negative reactions to a severe restriction in calories, so be careful if you decide to follow an especially restrictive diet.