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A Big Mac sandwich.

Earlier this week, New York City Mayor Michael Bloomberg unveiled his latest health initiative: encouraging workers to take stairs instead of elevators.

Since his election in 2001, Bloomberg has made it his mission to encourage healthier lifestyles.

A new study released this week by Carnegie Mellon University in New York takes aim at one of Bloomberg's biggest victories: forcing chain restaurants to post calorie information on their menus.

The study questions whether calorie postings have a real effect on what people consume, and found that even going one step further – providing customers with calorie recommendations – had no impact on the choices they ended up making.

The experiment:

Researchers camped out at two McDonald's restaurants in Manhattan and Brooklyn during lunchtime. As customers walked in, they were given a slip of paper containing one of the following: their recommended daily calorie intake, their recommended per-meal calorie intake, or no recommendation at all.

Afterward, the researchers collected receipts from the customers to see what they ended up ordering, and whether the recommendations had any effect on their ordering choices.

The consumer:

Of the 1,121 customers who participated, 44 per cent were men, and 53 per cent women. The recommended per-meal calorie intake for women is 640, but the average woman in the study consumed 766 calories. For men, the recommended per-meal intake is 800, but the average male who participated in the study consumed 756 calories.

The result:

The experiment showed that giving customers calorie benchmark information did not reduce the calories purchased.

In some cases, posting calorie benchmarks instead seemed to increase the number of calories consumed. If a Big Mac was 570 calories, for example, and the benchmark was set higher than that, researchers argued participants were prompted to order more.