People who are not significantly overweight will lose much more slowly, as do older people (particularly women). The article doesn't tell us the average age or weight of the participants.

Speaking for myself: I started Atkins about five years ago. At my age then (45ish, perimenopausal), most women gain weight. I've lost 35 pounds over the years, which doesn't seem like much averaged out, but considering I would have gained otherwise, it's more than it seems! My health has also improved over the time span many women's health deteriorates, so I am certainly not complaining.

Rachel