Many ways exist that you can use to lose weight. Some are good, whereas many are downright bad. All may drop your weight in the beginning, but some are unsustainable and risk damage in exchange for losing some weight fast without having to put in a lot of effort. These quick gains can cost you in the long run though, as staying with crash diets is impossible over time.
For instance, diets very low in calories sound logical. Since you have to burn more calories than you take in to lose weight, you may attempt to restrict yourself to something minimal to cause your caloric deficit. The problem is that your body does require a mimimum amount of calories to sustain metabolism and core functions. If you go below this for more than a day or two, your body is going to start going into starvation mode, which is both harmful to many physical organs and kills your metabolism and chances of losing weight.
Single food diets are aptly named, because you eat only one single food, and that is it. These diets can seemingly work miracles the first few days because of the caloric restriction which causes your body to flush out a lot immediately. However, you are depriving yourself of every mineral, vitamin and nutrient found in that food. Eventually, the deficiencies will cause both problems and compensatory binging.
Some diets blame a particular macronutrient and have you avoid it entirely. While your body can go in the short term without it, you only have so many reserves of it inside your body. When these reserves are depleted, you are going to start showing symptoms of not getting enough, and you are going to strongly crave foods containing it. This seriously limits the effective lifespan of such a diet.
Liquid diets are tempting for their extreme nature. Advocates will sometimes argue that it gives your digestive tract some downtime after years of working every day. There is limited research indicating that there can be health benefits to such fasting, but only in short and regular intervals. Going on a liquid diet for more than one day should only be done with the consent and supervision of your personal physician. There are miracle stories of highly obese folks weighing four to eight hundred pounds dropping lots of weight using liquid diets, but unless you need to lose that much weight, you should not assume that those approaches are right for you.
Diet pills are a huge industry, and largely unregulated, with many of the offerings untested in peer reviewed scientific research. If one particular pill really worked in getting everyone thin, then there would not be any obese folks left. Avoid these entirely.
When you first want to start dropping some weight, a crash diet can seem really appealing. You do not have to do much work, and you get quick results on the scales in the morning. However, in the majority of cases, the crash diet provider is really just offering a gimmick that drops your water weight with no real science. Dropping your unwanted pounds can prove difficult, but it is worth it for its proven results and safety.