The British Medical Journal compared commercial diets to structural medical interventions, and the commercial diets won. From the LA Times:
After a year, statistically significant weight loss was recorded in all groups apart from the primary care programs, but Weight Watchers was the only program to achieve significantly greater weight loss than the control group.
Clinical weight-loss programs are ones carried out in a medical clinic and patients have regular contact with a licensed professional such as a nutritionist or dietician. Supposedly they have more “rigor” and the advice is better, but are more expensive.
I have not read this paper yet, but supposedly it’s very good. The knock on these studies have always been the inability to control for people who drop out of the program. The people who finish lose 15-20% of the body mass, but the programs are brutal and have high attrition rates.
The programs have suspect long-term benefits even for people who complete the program. From another paper:
One randomized trial and several case series of medically supervised very-low-calorie diet programs found that patients who completed treatment lost approximately 15% to 25% of initial weight. These programs were associated with high costs, high attrition rates, and a high probability of regaining 50% or more of lost weight in 1 to 2 years.
So even though Weight Watchers and similar programs lack scientific purity, they do better than you’d think because they’re easier to stick with.
On the surface this might contradict the post written yesterday, but I think it’s more of a comparison of sticking with one of these diets vs. nothing at all, which is probably an improvement for many people. And over the long run sticking with Weight Watchers or Jenny Craig starts to look like a Mediterranean Diet in some ways, even if it’s not exactly the same thing.