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A group of corporate heavyweights including Hershey's, Kraft, Kellogg's and Coca-Cola announced last week that they had successfully made the U.S. marketplace healthier by reducing the number of calories on the shelf by 1.5 trillion.

While an expert applauded the move, she cautioned that there a lot of factors that come into play before it can be declared that Americans are getting healthier.

The Healthy Weight Commitment Foundation (HWCF), an organization led by 16 food and beverage companies, are continuing their campaign to reduce obesity in the U.S. and are attempting to do so by offering healthier, lower-calorie options at retailers across the country. This includes reducing the calorie content in some current products and reducing portion sizes of existing single-serving products.

“That number [1.5 trillion calories] thrown out there doesn’t necessarily mean something to me in terms of the individual, but it does show their commitment," said Katie Chapmon, a registered dietitian at Kaiser Permanente.

Culture, metabolism, and exercise are all part of weight management, said Chapmon, in addition to personal choice and preference. Just because Coca-Cola offers coconut water in addition to soda and Kellogg's releases a low-calorie cracker chip that shows up in the market snack aisle, doesn't mean people will necessarily choose these healthier options over others.

But Chapmon said that the brands included in the HWCF, such as PepsiCo, Campbell's Soup and General Mills, do have a certain advantage when it comes to connecting with the consumer.

“Many consumers grow up with these brands so they develop a sense of trust with their products," said the dietitian. She explained that people may be more likely to try a new, low-calorie product if it comes from a big name, reliable source.

Chapmon added that in order to choose these healthier products, they must be available to people in the first place. In South Los Angeles, where grocery stores are often sparse, many residents have to make a concerted effort to stock up on these goods.

“Offerings are limited to what’s close to your home,” Chapmon said.

But adding lower calorie foods to their roster of options isn't all for the public good; in addition to garnering them some publicity, it's also reaped financial benefits for many of the the companies. According to a study funded by the HWCF, lower calorie foods are driving sales for many of these corporations.

From 2007 to 2011, sales of lower calorie items by the HWCF companies studied increased by $1.25 billion — compared to less than $300 million for higher calorie products.

"Our industry has an important role to play in helping people lead healthy lives and our actions are having a positive impact," said Indra Nooyi, HWCF Chair and CEO of PepsiCo. "We see continued opportunities to give consumers the choices they're looking for and to work collaboratively with the public and non-profit sectors in initiatives that enable continued progress."

The Healthy Weight Commitment Foundation said they aim to reduce obesity in the U.S., especially among children, by 2015.