The best, and ultimately the simplest, way to lose weight and keep it off is to understand what works, what doesn't, and why, and then put that knowledge into practice. To put it simply, you need to educate yourself. Sadly, there are a lot of dangerous diets out there, and many others that simply don't work. This chapter is a consumer's guide to fad diets and other weight-loss schemes.What's wrong with this diet'If you spend ant time perusing the diet shelves of bookstores, or watching daytime television, or surfing the Internet, you are undoubtedly aware of an avalanche of diets: celebrity diets, low-carbohydrate diets, 3-day diets; diets designed to fit your blood type, astrological sign, age, gender, what have you. Most promise some sort of miracle, something quick and easy. And you may be tempted to give them a try.Yo-do dietingMost likely, you have dieted before. Maybe you lost a few pounds, maybe you lost many. But the reason you bought this book is that you gained them back again. This is the familiar diet yo-yo.Although some people say that yo-yo dieting messes up your metabolism and does lasting harm to your health, this is actually not true.Medical experts call it weight cycling, and this is what they have to say about it:Weight cycling does not increase the amount of your fat tissue.Weight cycling will not turn you into an "apple," causing you to regain lost weight as fat deposits in your abdominal area.The main thing wrong with yo-yo dieting is that it is discouraging.And the main cause of yo-yoing is diets that result in temporary weight loss rather than encouraging permanent changes in your eating and exercise habits.High-protein, high-fat dietsThe most popular diets today are based on the premise that being overweight is caused primarily by carbohydrates. These diets call for eating a lot of protein and little or no carbohydrates. Most of them also permit you to eat as much fat as you want. Their promoters claim this is a healthier way of eating.You undoubtedly know some people who have lost a great deal of weight, and quite quickly, on these diets. And it is hard to argue with success. But I'm going to do it anyway. High protein, low-carbohydrate diets are extremely unhealthy. The reasons for this are:They violate every known fact about nutritionally balanced eating.They ignore the established health risks of diets high in cholesterol and saturated fats.They overload you with protein, which results in loss of calcium from your bones, which may lead to osteoporosis. Protein overload also puts stress on your kidneys as they try to eliminate large amounts of urea, a by-product of protein metabolism.They forbid foods known to lower the risk of heart disease and many cancers.They deprive you of carbohydrates, the nutrient group most readily converted to energy. Even moderately active people will notice this lack during exercise.They deprive your brain of glucose, which it needs for normal functioning. The result is a slowdown in thinking and reaction time.They deprive you of the enormous benefits of fiber, which is found in carbohydrate-rich foods.They are deficient in essential vitamins.They cause potentially dangerous changes in your body chemistry.They deliver temporary weight loss. Weight gain is rapid once you go off the diet.Some "carbs are the enemy" diets are based on pseudo-scientific theories about insulin. Carbohydrates do not overstimulate insulin production in people whose insulin-secreting cells function normally. The best way to ensure that you do not have an "Insulin problem" is to have a blood glucose test as part of an annual preventive health examination. If your blood sugar level is abnormal, your doctor will investigate the cause and discuss dietary changes with you. If your blood sugar is normal, the healthiest thing you can do is to ensure that 55 to 60 percent of your daily calories come from carbohydrates, primarily complex carbohydrates.The rapid weight loss seen in people on low-carb diets is mostly due to water loss.Protein metabolism produces urea, a toxin eliminated in urine through the kidneys. Every gram of urea requires 50 ml of water to flush it from the body. That's a little more than an ounce of water, and remember: A fluid ounce of water weighs an ounce. In addition, fat metabolism produces ketone bodies, another toxin that increases water loss.