All of the popular weight loss programs will work, as long as you stick to it, finds a new study involving McMaster University.

The study found "minimal" differences in popular programs such as Jenny Craig and Weight Watchers.

"I think this is a really nice, important message. The good news is they work," said Bradley Johnston, the study's lead author. "The take-home message is people don't have to fret over the type of diet they choose."

The key, said Johnston, is support and the ability to stick with whichever diet program you choose.

Diets with support and exercise enhance the chances of weight loss, said Johnston, who is an assistant professor of clinical epidemiology of the Michael G. DeGroote School of Medicine at McMaster University and clinical epidemiologist and scientist at Toronto's Hospital for Sick Children.

"Adherence is the key factor," Johnston stressed. "The fundamentals of losing weight have not changed."

The study was published Tuesday in the Journal of the American Medical Association.

Diet programs studied were Atkins, Weight Watchers, Zone, Jenny Craig, LEARN, Nutrisystem, Ornish, Volumetrics, Rosemary Conley, Slimming World and South Beach.

It involved a major analysis of 48 trials of "branded diets" and included more than 7,200 overweight and obese adults.

The study found there was little difference in weight loss among programs that promote low-carb diets and those which stress a low-fat diet. After a six-month followup, people on low-carbohydrate diets lost 19 more pounds than those who were not on a diet, while those on low-fat diets lost 17 more pounds than those on no diet. After 12 months, about two to three pounds of that difference was gone and there was no difference between low-carbohydrate and low-fat diets.

The study was needed, adds Geoff Ball, associate professor and an obesity expert in the Faculty of Medicine & Dentistry at the University of Alberta who was involved in the study.

"Given the popularity of these diets around the world, there has been a real lack of research to examine their relative benefits. But, overall, the differences between the different diets regarding their impact on weight loss were relatively small."

Funding for the study came from the Canadian Institutes of Health Research and the Public Health Agency of Canada.