Oprah backs Weight Watchers, but is it the best diet plan?

Oprah Winfrey added to her fortunes (reportedly about $45 million in a single day) with the announcement that she now owns 10 percent of Weight Watchers. In addition, the media mogul will serve on the board and will use the system to tackle her ongoing battle with her weight.

“Weight Watchers has given me the tools to begin to make the lasting shift that I and so many of us who are struggling with weight have longed for,” said Winfrey in a statement.

No doubt a little backing from Oprah will give the struggling brand a boost, but is it the best plan for weight loss?

Consumer Reports magazine offered some answers in a 2013 survey of thousands of dieters. They asked about both commercial and DIY diets, but for our purposes we'll just take a look at the big four commercial brands: Jenny Craig, Medifast, Nutrisystem and Weight Watchers.

Weight Watchers is most popular: Of the dieters surveyed, 43 percent signed up for Weight Watchers and it received a score of 74, one of the top scores for commercial diet plans (but middle of the road when compared to DIY methods). Nutrisystem was ranked lowest for commercial diets with a score of 56.

Medifast users lost the most. If weight loss is the sole goal, the Medifast program is the way to go. These users lost more weight, 20 to 43 pounds for men and 14 to 40 pounds for women, than those on any other diet program. And they spent a median six months on the program. Here's how the other plans compare:

  • Jenny Craig users lost 15 - 34 pounds (men) and 10 - 30 (women) over a median nine months.
  • Nutrisystem users lost 10 - 30 pounds (men) and 7 - 24 (women) over a median five months.
  • Weight Watchers users lost 12 - 35 pounds (men) 10 - 28 (women) and over a median nine months.

Of course, as CR reports, it is possible to lose weight on any eating plan. You just have to find the one that best fits your lifestyle and preferences and you must have realistic expectations. While many survey respondents said they wanted to lose 40 pounds, only 13 percent were able to get within 5 pounds of that goal. One of the best practices for any diet plan, is to track your calories and your level of activity, whether you do it with pen and paper or use an app like My Fitness Pal .

Jenny Craig, Medifast, and Nutrisystem all involve the use of branded, packaged, portion-controlled meals and foods which you then supplement with fresh produce. The users of these programs said they relied heavily on the packaged products while dieting. The problem is, those foods don't always taste so great. A full 38 percent of Nutrisystem users did not like the taste of the food compared to 23 percent of Medifast users and 17 percent on Jenny Craig. But if you don't cook, these plans may be the best choice.

Many dieters on these three plans also said they spent more than they expected to spend. For the first three months, Jenny Craig clients spent a median of $809, Medifast dieters $677, and Nutrisystem customers $582. Weight Watchers costs were not reported as they do not involve packaged foods and will vary by individual.

Weight Watchers, while less dependent on packaged foods, is really about having a support system. They now offer online only memberships and personal coaching, but the meetings are the foundation of the brand and the users who attended monthly meetings are the ones who lost the most weight.

So who knows?  Oprah has been making a lot of surprise appearances in Atlanta this week . Maybe she'll end up at a local Weight Watchers meeting.