North Americans spend $550 billion dollars per year on weight loss products and programs, according to the Canadian Medical Association Journal. (CBC)

Keep it simple: that's the new expert advice for people who are trying to shed a few pounds.

In Thursday's New England Journal of Medicine, researchers asked 811 overweight adults to follow one of four popular diets with varying amounts of protein, fat and carbohydrates.

'It's not so much whether that food is carbohydrate-rich or protein-rich. It really comes down to calories, a very simple message.'— Dr. Frank Sacks

Participants were also told to slash 750 calories a day from their diet, get 90 minutes of moderate intensity exercise a week (such as brisk walking), keep an online food diary and meet regularly with diet counsellors to track their progress.

"It's the amount of food you put in your mouth," said study author Dr. Frank Sacks of the Harvard School of Public Health in Boston. "It's not so much whether that food is carbohydrate-rich or protein-rich. It really comes down to calories, a very simple message."

The diets were similar to commercial plans, and all contained healthy fats, were high in whole grains, fruits and vegetables and low in cholesterol.

People lost 19 pounds on average after six months, and most of them saw the needle on their scales start to creep back up after a year.

Among the 80 per cent who completed the two-year program, the average weight loss was about nine pounds, and waistlines shrank an average of five centimetres, or two inches.

About 15 per cent of the dieters lost 10 per cent or more of their starting weight.

People who went for regular counselling shed about 22 pounds compared with an average of nine pounds for those who did not attend meetings.

Community approach advocated

"Even these highly motivated, intelligent participants who were coached by expert professionals could not achieve the weight losses needed to reverse the obesity epidemic," Martijn Katan of Amsterdam's Free University wrote in a journal editorial accompanying the study.

Instead, it may be better to adopt a community-based approach, Katan said. He pointed to a project in two small French towns that used a widespread effort to get school children to eat better and move more.

After five years, 8.8 per cent of the children were overweight compared to 17.8 per cent in neighbouring towns.

"Like cholera, obesity may be a problem that cannot be solved by individual persons but that requires community action," Katan wrote.

"It is an approach that deserves serious investigation because the only effective alternative that we have at present for halting the obesity epidemic is large-scale gastric [weight-loss] surgery."

Likewise, a report released Thursday by the American Institute for Cancer Research and the World Cancer Research Fund also recommended co-ordinated efforts by all sectors of society to help individuals eat well, get active and maintain a healthy weight to reduce the burden of cancer worldwide.

But time constraints are part of the reason experts say society is still overweight. Mixed messages on what's best to eat add to the confusion.

For Lynn Gillman of Ottawa, it took years to figure out how to shed her excess pounds. After years of dieting, she tracked calories until she dropped 70 pounds.

"It's a lot of work," said Gillman. "You have to commit, you have to plan, and you have to know it's going to take you a long time."