Researchers in obesity are studying the effects of vitamins and even plate size on people's appetites.

Health experts have gathered in Winnipeg for the annual conference of dieticians. Many say obesity isn't just about food.

"We're simply not spending the same level of energy...the result is, we continue to store fat (and) obesity rises," says Dr. Arthur Quinney of the University of Alberta.

One-third of Canadians are overweight and 12 per cent are obese, defined as weighing 15 kg more than normal.

Canadian dieticians were told the rate of obesity in children in the country has doubled in the last few years. Obesity increases the risk of heart disease and diabetes.

"Vitamin supplementation might be helpful to facilitate appetite control," says Tremblay.

He's also looking at other factors.

"If you have a very large plate, it might promote a distortion in appetite control, you might be inclined to eat more," says Tremblay.