People unknowingly "booby-trap" their own homes in a way that can lead to overeating, according to an American nutritional expert who has conducted hundreds of food studies.

Brian Wansink told a joint meeting of the Canadian Diabetes Association and the Canadian Society of Endocrinology and Metabolism that some people blame obesity on fast food, the government and food companies, but the food fight really begins at home.

The solution isn't concentration and willpower, he told more than 3,000 delegates at the Metro Toronto Convention Centre on Thursday.

"One thing we can start doing is start re-engineering our environment so it mindlessly works for us, rather than against us," said Wansink, the director of the Cornell Food and Brand Lab at Cornell University.

Most people overeat because if food is put in front of them, they'll eat it, said Wansink, whose team has led companies to introduce smaller, 100-calorie portions.

Secret weighing

One study involved two groups of graduate students serving themselves Chex snacks from either large serving bowls in one room or smaller serving bowls in another room at a Super Bowl party. Their individual bowls were surreptitiously weighed, and it was found that those who served themselves from large bowls took portions that contained 53 per cent more calories, he said.

The bowls were coded, so that leftovers could also be tracked, and it turned out that the group that served themselves from large bowls also ate 59 per cent more food, in general, than the group that served themselves from smaller bowls, Wansink said.

Another study, conducted at a Chicago movie theatre, showed that people will even eat food that's not very good if it's in front of them.

Moviegoers at the Mel Gibson movie Payback were given buckets of popcorn — either freshly popped or five days old and rancid.

"When people ate it, it didn't even crunch, it sort of squeaked," he said as he described the old popcorn, eliciting groans and laughter from his audience.

Much of the fresh popcorn was quickly gobbled up before the credits finished running before the movie, he said. As for the recipients of the old popcorn, they would taste it, put it down, wait a few minutes, then try again.

Diet tips

Wansink also said his research has shown that people can reduce their intake by replacing wide, short drinking glasses with tall narrower ones, and using smaller serving spoons.

In addition, he said, plates should be filled before they're served at the table and serving bowls should be kept off the table to avoid mindless refilling.

Sharon Zeiler, senior manager of nutrition for the Canadian Diabetes Association, welcomed Wansink's research, and said dietitians have employed many of these techniques. "Anything with science now is becoming extremely evidence-based, and so it's wonderful to have good strong evidence," she said.

About 35 to 40 per cent of Canadian meals are eaten in restaurants, Zeiler noted, adding that the research can be applied by restaurant owners and people who eat at home.

Buffet-style restaurants could put salads out in smaller bowls — and that would encourage people to take smaller portions, she said.

And for at-home buffets on occasions such as Thanksgiving, Zeiler said the hosts could use two small bowls for mashed potatoes, rather than one huge bowl.

Food and nutrition are hot topics at the conference. Canada has more than two million diabetics, Zeiler said, and being overweight and not getting enough physical activity can be contributing factors for people with Type 2.

Many people have the disease but don't realize it until symptoms including blurry eyesight or hypertension lead to a diagnosis, she added.