In a recent study reviewed by Dr. Briffa they maintain all diets are equal and that it is after all only calories that matter, no matter what the diet. I do think calories matter - absolutely and it is important to eat less on any reducing diet (there is some evidence to support more calories are allowed on a low-carb diet, but I'm not even going to go there) - however, I maintain all diets are not equal for everybody. People with insulin issues do best on a low-carbohydrate diet to do an end-run on the enormous insulin output in response to eating carbohydrates and subsequent hunger and cravings that leads to overeating or, when willpower is invoked, an almost impossible task to diet without gnawing hunger. That insulin produced in overabundance in a person who is insulin resistant (see it as the doors to the cells no longer as sensitive to the hormone, so more of it has to be produced to get the job done)is the hormone for storing fat - too much insulin, too much fat storage (instead of being an energy producing "machine", suddenly one becomes a fat storing "machine"). Too high blood sugar, too much insulin to correct that and too much fat storage as a result - this is seen in middle-aged people who have "bellies" (fat storage there) and, therefore, obvious insulin resistance to varying degrees.
Excellent, somewhat humorous and well thought-out article by Dana Carpender refuting the study: Refutation by Dana Dana figured out people were eating about 140 grams of carbohydrate on the supposed low-carb diet - a far cry from the 20 to 60 grams of carbohydrate per day that most people do on a true low-carb diet.
Incidentally, I myself have a tendency towards the "apple" shape. I am definitely not pear-shaped.