Those calories consumed over the holidays are not just numbers. They are not just plain calories. Food calories are kilocalories, or 1,000 physics calories.

A calorie is the unit of heat that became standardized throughout the scientific community as the amount of heat needed to heat 1 gram of water by 1 degree Celsius. This was through the study of combustion and chemical reactions.

Physics judiciously defines mechanical work as force multiplied by the distance over which the force acts. The unit known as a joule is the work done by one Newton force acting over 1 meter.

In vertical lifting, one joule is the work required to lift 3.6 ounces (1 Newton) 3.3 feet (1 meter). That is about the work done lifting two golf balls from knees to ears.

It is obvious that doing work can produce heat, as evidenced by rubbing one’s hands together. But how much work produces how much heat?

The difficult task for our forebears was determining whether the heat produced by friction was the same kind of heat as that produced by combustion. Nineteenth-century scientists did not know enough about physical processes to be sure whether heat was a type of energy or something else.

Since the joule defined a unit of work/energy and the calorie a unit of heat, no one knew whether the two were equivalent. Heat produced by work was too difficult to measure because it took a lot of work to produce significant heat. In addition, too much heat escaped into the surroundings, and there was no way to capture it all.

The joule is also a unit of energy, as demonstrated by the work of James Joule, an English scientist. Joule provided the definitive data with 30 years of studies and ingenious experiments that used measurable mechanical work to heat water by capturing all of the heat.

Considering what a small amount of heat a calorie is, it is not surprising that the relationship between calories and joules took a long time to verify. In human- size terms, a joule is a very small unit, even smaller than the calorie: It takes 4.2 joules to make one calorie.

To put the above golf ball exercise into perspective, it would require lifting the two balls a little more than four times to produce 1 calorie, or 420 times to produce 100 calories.

But wait! These are physics calories. Food calories are kilocalories, 1,000 calories each. Formerly, food calories were written with a capital “C,” but that practice got lost in the depths of consumer packaging.

So to burn 100 kilocalories (100 food calories) would require lifting the two golf balls 400,000 times. Equivalently, one could lift a bowling ball only 5,625 times.

That 200-calorie holiday dessert does not seem so carefree now, does it?

One hundred food calories is also equivalent to the work done by a 150-pound person climbing 600 feet in height. That is 60 floors or just a little more than a hike up the Diamond Head trail.

Of course, there are more entertaining ways to work off those dietary calories, but it is unarguably easier to add them than to subtract them.

One good thing about work, energy and heat is that there is no time involved, so doing 100 kilocalories (428,000 joules) of work could occupy a few minutes or take months. To burn the calories faster requires greater power, which is energy divided by time.