The key to making effective weight loss decisions is to find a weight loss plan that you can use to maintain that weight loss for the rest of your life. Any diet which restricts your calorie intake to less than the calories your body is burning will work, short term. The vast majority of diets are designed to do just that (work short term). To keep the weight off long-term, you have to exchange your unhealthy eating habits for healthy ones. These new eating habits have to be incorporated into your life to the extent that you do them automatically. To work long term, you also have to incorporate at least a minimal amount of regular exercise into your life.
Diets that promise that you'll lose a large amount of weight quickly without changing your eating or exercise habits usually do not work at all unless the weight loss is caused by some sort of supplement such as diet pills or foods that raise your metabolic rate. These types of diets usually claim that their pill or patch or fat blocker will give you miracle results. Some of these types of diets actually work but none of them work for the long term and most people start regaining the weight as soon as the stop taking the pill or eating the exact combination of foods, etc.
Low carb diets are very effective weight loss plans, especially for men, over the short term. Low carb (or high protein) diets work by restricting the amount of carbohydrates you are allowed to eat to under 10% (usually) and increasing the amount of protein and fat you consume (to 40% to 60%). When you restrict carbohydrates, your body goes into a metabolic state called ketosis, where the body burns fat instead of carbs for fuel. Short term, this works great. Long term, however, this type of diet is believed to cause medical problems such as kidney failure, high cholesterol, kidney stones, gout, heart disease and even osteoporosis. The Atkins Diet and the South Beach Diet are the two most well known low carb diets.
Meal provider diets also work short term and are especially good for those dieters who lack the discipline (or the time) to follow less regimented diet plans. A meal provider diet is one in which most, or all, of your calorie restricted meals and snacks are delivered to you by the weight loss company. Sometimes these meals are true meals and sometimes they are merely nutritional drinks/shakes or meal bars. Some of these types of diets are one-size-fits-all and some can be, at least somewhat, tailored to your likes and dislikes. The downsides to these types of diets over the long term are the costs involved, the restricted menus choices and the restrictions they place on your life. Jenny Craig and Nutrisystem are two of the best known meal providers.
Starvation diets are highly touted in some circles. These diets, however, are not designed to be used long term and should always be used at the direction (and under the guidance) of your medical doctor. Diets of less than 800 calories a day fall into this category. Since we define an effective weight loss program as one you can use forever, we do not recommend you ever choose this option unless medically necessary and directed by your physician.
The bottom line is: Don't fall for miracle no effort, no lifestyle change weight loss claims. For a permanent solution to your weight problem you have to select a plan that you can adopt and maintain for life. Successful weight loss diets encourage permanent healthy changes to your eating and exercise habits. Taking small baby steps and realizing this is a journey of a lifetime not a sprint will allow you make effective weight loss decisions and choose the right diet for you.