NATIONWIDE — Weight loss isn't easy. And with countless programs and plans out there it's easy for your members and clients to get lost in the weight-loss world.

To help with the confusion, here are three new studies that shed some light on which diets are best and — surprise, surprise — dieting may not be all that it's cracked up to be.

Two recent studies on popular diet plans found that no plan is better than another, but no plan is really a standout winner either — unless of course you put in the hard work.

In a review of many weight loss studies, the Jan. 4 issue of the Annals of Internal Medicine looked at Weight Watchers, Jenny Craig, L.A. Weight Loss Centers, eDiets.com, Take Off Pounds Sensibly, Overeaters Anonymous, Optifast, Health Management Resources and Medifast/Take Shape for Life.

The article's authors found reviewing the research to be difficult because those who dropped out of diet programs weren't included in the research results of most of the studies, making those studies of little value, the authors said.

“With the exception of Weight Watchers, the evidence to support the effectiveness of major commercial weight-loss programs is limited,” authors of the study wrote in a summary statement. “Patients considering the use of commercial weight loss programs should realize that these programs have not been carefully studied and that they vary greatly in cost.”

Another study, this one in the Jan. 5 issue of the Journal of the American Medical Association, compared the Atkins, Ornish, Weight Watchers and Zone diets.

After assigning 160 participants to different plans, participants had to strictly follow their assigned diet for two months. For the remainder of the year, the participants could follow the plan as much as they wanted. And guess what? This time all of them were almost identical in weight loss and health benefits.

“Each popular diet modestly reduced body weight and several cardiac risk factors at one year,” authors of the study wrote in their conclusions. “Overall dietary adherence rates were low, although increased adherence was associated with greater weight loss and cardiac risk factor reductions for each diet group.”

And, finally, if you had any doubt in your head, it's official; fast food isn't good for you, your health or your waistline.

A study, published in the January issue of the Lancet, tracked the fast-food visits of more than 3,000 men and women ages 18 to 30 for 15 years. Researchers found that regardless of how much participants ate and exercised, those who ate fast food regularly (two or more times per week) gained about 36 pounds over the period of the study compared with 26 pounds for those who ate at McDonald's, Burger King, Wendy's, Arby's, Pizza Hut and Kentucky Fried Chicken less than two times per week.

Overall, the message is clear.

“If a fitness facility wants to promote research-based approaches to long-term weight management and disease prevention, it should offer educational programs, services and/or support groups that are in line with what the research tells us is beneficial for people long-term — not quick fixes that can't possibly be sustained one year or five years down the road,” Cynthia Sass, registered dietician and spokesperson for the American Dietetic Association, said.