Diet and Weight LossWeight loss with dieting is a process. Generally there is an initial weight loss, followed by a plateau period followed by a slow and gradual gain in weight. The key to successful long term weight loss is minimizing the eventual weight gain. 
It is important that patients fully understand this concept otherwise they will become frustrated when their weight loss reaches a plateau. This is a dangerous time for dieters because they are doing all the right things, but they've stopped loosing weight. It can be very frustrating - so frustrating that patients start to increase their caloric intake and Zoom - the weight goes back on faster than it was lost because the patient's metabolic rate has slowed to compensate for the caloric reduction. All these new calories are stored as fat and the result is that chronic repetitive dieters generally have a net gain in weight over the years. Diet therapyThe first course of action for most patients trying to loose weight is dieting. The rational is simple, if you consume fewer calories than you need you'll lose weight. This is not rocket science, but you may have to be a rocket scientist to follow the arguments for all of the available diets. 3500 calories is equivalent to 1 pound of fat. Eat 3500 calories more than you need and you'll gain a pound, eat 3500 calories less than you need and you will lose 1 pound of fat. 
3500 calories is a lot of calories to cut out of a diet all at once. Patients should beware of diets that promise a five pound weight loss in the first week. They will have to eliminate 17500 calories to accomplish this goal - almost impossible unless their diet consists entirely of Pepsi and potato chips. Patients who are not gaining or losing weight are in a caloric balance - the calories that are consumed are used as energy. If a patient is gaining weight he/she is consuming more calories than necessary. The body doesn't distinguish where the calories come from - an apple or a chocolate bar. It just knows that if more calories come in than needed to "run the plant", those calories will be stored as fat for future use. (if a patient who is in caloric balance eats 1 apple a day more than needed, he will gain 10 pounds in a year! 100 calories per apple x 365 days = 36500 calories) The "big secret" then to weight loss is to eat fewer calories! This should be no great surprise. The way to keep it off is the bigger issue, but more on that later. Unfortunately patients don't often want to hear this information. What they really want is a quick and relatively (or completely, if possible) painless way to lose the extra pounds. Fortunately (or unfortunately) for these patients there are lots of enterprising people who are happy to sell them just want they want. For a few dollars (sometimes more than a few for as we all know, the more expensive something is the better it is.) they can buy the latest diet, or tonic or exercise machine to help them "melt the fat away". There are lots of diets available. In fact diet regimens are a "growth" industry. Examples include the Atkins diet, the GI Diet, the South Beach Diet, the Zone, and the old low fat diet, to name a few. Do they work? Is one better than another? 
Well, the studies aren't great. Bravata(1) did a metanalysis of articles looking at low carb diets. As one would expect most of the studies were conducted with small population samples (As many as half of the studies were very small, with fewer than 30 participants, and some studies had as few as two participants. The largest study had 162 participants), and were of short duration. (You have to stop the study before patients start to regain lost weight if you want to make an impression. Remember the process). Given that, any analysis could be little more than speculative. What emerged, though, was that among obese people, weight loss was associated with longer diet duration and restriction of calorie intake rather than carbohydrate content. There was no significant effect on serum lipids, fasting glucose or insulin levels, or blood pressure with low carb diets.
Foster (3) looked at subjects with a lower BMI (average 34) and without diabetes. 63 patients were randomized to either a low fat diet or the Aitkin's diet. The findings were: More people stayed on the low carbohydrate diet than on the conventional diet, though the difference was not significant. The average weight loss was greater in the low carbohydrate than in the conventional diet at three and six, but not 12 months. The low carbohydrate, but not the conventional diet, led to a 20% reduction in serum triglyceride, and about a 20% increase in HDL cholesterol, but not total or LDL cholesterol. There was no change in blood pressure in either group. So what do these studies tell us? Well, patients tolerate the low carb diet better and loose more weight with it (at least initially). Low carb diets may offer a modest advantage with respect to insulin resistance and trigylceride reduction. However, the key to success is in reducing caloric intake and persisting with this reduction. Ultimately it is probably best to tailor the diet to the patient, and complement the diet with an exercise program, as well as some behaviour modification techniques. Depending on the patient, pharmacotherapy may also play a role. How do people who are success at weight loss do it?How do they maintain weight loss? Weight loss is attained with a combination of diet and exercise (90%), restriction of foods (88%), monitoring of portion control (44%), counting of calories (44%), using a low fat diet (33%), or an exchange diet (22%). They maintain weight loss by being regular breakfast eaters (90%), weighing themselves weekly (75%), pursuing a high level of physical activity, eating regular meals and eating out less than once a week. References:
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