When was the last time you bought a half-gallon of ice cream or a pound of coffee.

The question arises because of the recent publicity about candy maker Mars preparing to make some of its candy bars, including Snickers and Mars smaller, in the name of reducing the number of calories to 250 apiece. That’s 4% less of a Mars candy bar and 11% less of a Snickers. The change will come in 2013.

Click on the Mars candy bar above to see some other products that have gotten smaller.

Mars has not said it will reduce the price.

Chances are, it won’t. Food companies have made their products smaller for years rather than increase price. It happens every time the economy struggles or commodity prices rise. Grocery store shelves carry per-unit prices of many products so savvy consumers can see the price rise but how many check?

When profits are pinched, a company has three options: raise the price, substitute lower-cost ingredients or make the product smaller, says Cal State Fullerton marketing professor Chiranjeev Kohli. While he argues that most consumers can’t remember exact pricing of most products they buy, they are more aware when the price goes up than when they get a little less for the same price.

For years most ice cream has been sold in 1.75 or 1.50 quarts instead of half-gallon (two quarts) containers. And most brands of coffee come in 13-ounce or even 10.5-ounce containers instead of the old 16-ounce (pound) can. (And coffee doesn’t come in cans anymore, but that’s another story.)

Companies have many ways of subtly reducing the amount of product customers: fewer saltine crackers per stack; an indented bottom on peanut butter jars so they hold less; cereal boxes that are the same height and width, so they look the same on the store shelf, but they’re thinner; fewer squares on toilet tissue rolls.

So is Mars merely being creative about a de facto price increase or does it really care about its’ customers’ waistlines? And does it matter?

Mars isn’t the first food company to shrink its product in the name of cutting calories. Notice that it didn’t choose to remove the sugar to cut calories. In 2004 Kraft introduced a 100-calorie pack of several of its brands include Oreo Thin Crisps. More than 250 100-calorie products were on the market in 2009, according to Tom Vierhile at Datamonitor.

However, Adweek reported that sales dropped dramatically during the recession because consumers looked for greater value. Most of these 100-calorie packets cost more per unit than their regular counterparts.

Companies are creative in explaining their smaller packages. Honeyville Grain’s website says its “small packaging is a result of thousands of customer requests for smaller, more management packages.”

A Kraft spokesman told the New York Times that putting 15% fewer Nabisco Premium saltines in a box makes them more portable and fresher.

“Portable. I don’t buy that and I don’t think consumers do,” said marketing professor Kohli. “Healthier I can buy because there is evidence that smaller portions are better for people. But will people actually eat less or buy two (candy bars).

“Some people think (shrinking product size) is sneaky,” he added. “I haven’t seen empirical research about the damage that does to consumer trust. But it’s a relatively old practice.”