There are many diets promising quick weight loss. How do i know which one will produce results?

While there is no set approach to identifying a ‘fad diet’, many have few or all of the following characteristics:

• Recommendations that promise quick weight loss. People are often willing to try anything that promises to help them lose weight. They would rather adopt a specific diet plan that will produce dramatic results rather than make the effort to lose weight through long-term, permanent changes in eating and physical activity. A diet that is successful long-term cannot work immediately; it takes time to gain unwanted weight, and therefore it takes time to lose it. Slow gradual weight loss increases the chances of successful weight loss and maintenance, long-term.
• Claims that sound too good to be true. Fad diets thrive on misleading weight loss claims, which often do not have the backing of scientific research. 
• Recommendations are based on a single study. It is not feasible to make generalised conclusions or recommendations based on the findings of one study. A number of studies are required to form the basis of any scientifically proven weight loss approach.
• Dramatic statements or conclusions that are refuted by reputable scientific organisations. Reputable scientific organisations tend to support weight loss approaches where there is sufficient scientific research to back up the weight loss claims or statements made. Often, such organisations will refute the statements or conclusions made by fad diets because they do not follow set criteria.
• Lists of ‘good’ and ‘bad’ foods. They overemphasise a particular food(s) or type of food(s) and eliminate others. However, there are no ‘good’ or ‘bad’ foods; eating in moderation will ensure you achieve good nutrition and food variety.
• Recommendations made to help sell a product. There is always a ‘money making’ side to fad diets. Often they tend to promote a product, supplement, equipment, etc which is portrayed as an essential requirement of the weight loss plan. These are not necessary, and most of the time they do not work or make no difference.
• Recommendations from other studies that ignore differences among individuals or groups. Everyone is different in how they respond to changes in eating patterns. A successful eating plan should accommodate people with diverse needs and food preferences.
• Eliminates one or more of the five food groups. Fad diets often don’t encourage you to eat a well balanced diet that includes a variety of foods. By eliminating one or more of the five food groups, and therefore limiting food choice, you miss out on those nutrients found in foods that make up the food group(s). Development of nutritional deficiencies is likely if the diet is followed long-term.
• Do not encourage physical activity, or imply that weight can be lost and maintained without exercise. Regular physical activity is an essential component of weight loss; weight loss and maintenance without physical activity will ultimately fail. In addition to weight control, there are other benefits associated with regular physical activity such as reducing the chance of developing heart disease, and improving health and overall wellbeing.