So, it all comes down to calories. But not all calories are created equally!
At the end of the day, it all boils down to eating less calories. What goes in, must be less than what comes out. The amount of calories you consume must be lower than the amount of calories you use. Even high protein low carbohydrate diets that say "all you can eat meat" eventually lead to a loss of appetite and decreased total caloric intake. That's the only way you are going to lose weight. Eat way less than before.
Nearly every diet tries to reduce caloric intake, either directly or indirectly. High protein diets lead to anorexia (loss of appetite) and an eventual decrease in caloric intake, even though they say you can eat as much as you want. Other diets limit your caloric intake directly by having you count points or sending you prepared meals.
Studies have shown that most people severely underestimate the amount of calories that they consume on a daily basis. When questioned, most Americans think that they consume about 1200-1500 calories per day. However, when these same people were tracked, it turns out that many were consuming 3000-4000 calories per day. This is ok when you are 18 years old and playing high school sports, but not ok when you have a desk job and don't have time to run around.
Even simple, unscientific polls on various websites have shown that 68% of respondents answered that they consumed between 500-1200 calories per day. Another 9% felt that they consumed between 1200-1600 calories per day. That's unbelievable. We all know that Americans readily consume between 2800-4000 calories per day.
Most humans require far less calories than they consume. The average American male rarely needs more than 1600-1800 calories to maintain their current weight, and the average female rarely requires more than 1400-1700 calories. Of course, most Americans consume 2000 or more calories per day. Some consume as much as 5000 without even noticing it.
Of course, if you weigh 300 pounds, you will require more calories to maintain your metabolism. If you weigh only 150 pounds, you will require less calories for maintenance metabolism. As you lose weight, your overall caloric requirement goes down, and you should adjust your diet accordingly.
If you reduce caloric intake, you will lose weight. It takes discipline. But it works. Certain diets help you reduce your appetite by having you eat foods that don’t lead to hunger. Atkins and South Beach do this by reducing carbohydrate intake drastically.
Not all calories are created equal. One hundred calories of plain white sugar cause an instant spike in your blood sugar levels and start the fat storage process. While one hundred calories of asparagus don't affect your blood sugar levels at all. Keep that in mind when you are trying to decide how much of each food to eat.
The C3 Diet doesn't require you to count calories or eat drastically less. You just have to eat the correct foods. You can eat as much as you'd like, as long as it is of the right foods. Of course, if you eat loads and loads of high glycemic index fruits, you will still gain weight. So be reasonable and follow the diet closely.