different folks, different diets

This should surprise no one:

David Ludwig and his colleagues at Children's Hospital Boston put 73 obese young adults on either a low-fat or a low-glycaemic load (GL) diet, which limits intake of quickly digested carbohydrates, such as white bread and refined breakfast cereals, that rapidly raise blood sugar and insulin levels. Participants were encouraged to eat until satisfied without counting calories.

They found that people who naturally produce high levels of insulin - a hormone that encourages fat and liver cells to store energy - fared better on low-GL diets, where blood sugar levels rise more slowly than on low-fat diets. They lost an average of 5.8 kilograms over 18 months, compared to just 1.2 kg for people on the low-fat diet. They also lost significantly more of their body fat (The Journal of the American Medical Association, vol 297, p 92).

Everyone's dietary needs are different, and anyone who tells you differently is trying to sell you something. Probably a fad diet.