Consumer and health groups are putting the blame for growing waistlines on supersize portions at fast food outlets. Meanwhile, McDonald's has unveiled a new menu of healthier options.

A U.S. group called the National Alliance for Nutrition and Activity said Tuesday that the "value-sized" meals offered at fast food restaurants manipulate customers into eating far more calories than they need. It's one growing trend that has led to another -- growing obesity rates.

"We're supersizing our kids and supersizing ourselves," says Melanie Polk, a dietitian at the American Institute for Cancer Research.

People think they're getting a bargain when they order extra-value meals, but really, they're just getting extra calories. Upgrading to a large fries and drink, for example, will add about 500 extra calories to a meal -- about a quarter of the daily caloric requirement for most people.

The problem is, it will also save you some money.

Believe it or not, it costs more to purchase a McDonald's Quarter Pounder with Cheese, small fries and a small Coke separately than it does to buy the Quarter Pounder with Cheese as part of a large Extra Value Meal.

Health groups say that ordering smaller portions will send a message to the food industry that consumers are looking for value without the hefty calorie count.

"We can speak up. Say 'small,' say 'half,' say 'share,'" says Polk.

Toronto dietitian Rosie Schwartz says consumers should put their money where their mouth is. "Patronize places where you're not penalized for wanting lower fat food," she told CTVNEWS.com.

Some chains are already getting the message. Tuesday, McDonald's Canada unveiled a new line of lower fat offerings. The "Lighter Choices" menu includes choices like salads, veggie burgers and a grilled chicken sandwich.

The new McVeggie Burger rings in at 323 calories compared to a Big Mac with 574 calories. But the cost of items on the new menu remains higher than the other offerings -- for example, the roasted vegetable and chicken salad and a drink will set you back at least a couple more dollars than any full-fat sandwich combo.

It's not the first time fast food giant has tried a healthier menu. In the past offerings have included salads and the McLean Deluxe, a low fat burger. But poor sales and, many said, unappetizing products, prompted McDonald's to shelve the more nutritious eats.

"We tried salads seven years ago at McDonald's and consumers weren't really interested in them. There was very little demand," says Bill Johnson, president and CEO of McDonald's Canada. "With the change in consumers' eating habits over the last few years, now we know there is more of a demand."

Schwartz says with people eating out more often, the availability of lower fat options is a step in the right direction.

"People can get the higher fat food one day and get the lighter choice the other day," she says.

And if the lighter choices don't appeal, Schwartz says it's still possible to cap calorie counts.

She recommends opting for a single burger instead of a double patty and says to pick grilled chicken sandwiches over fried choices.