His shoulders are slouched. His eyes vacant. His words distant, yet somehow matter-of-fact.

He says, “Normal? I don’t know. I don’t know what normal is. I thought I did once. I don’t anymore.”

That’s Dr. Bill Stockton’s response to a friend suggesting a block party as a way of getting back to “normal.” This occurs at the conclusion of an especially chilling Twilight Zone episode, “The Shelter,” after another friend assures the doctor that those who attended his birthday party will pay for the damage done to his house.

The partygoers do not get out of hand during the party, however. They do so after. After they hear a nuclear bomb could be headed their way ...

And the doctor refuses them entry into his family’s filled-to-the-brim bomb shelter.

Not too long ago, I felt a little bit like the doc, but I wasn’t assessing house damage done by my three best friends. I simply looked at the number of calories per serving listed on the brand of green beans I’ve been using for years.

I didn’t see the number I had always seen before: 20. I saw 15. Fifteen? Fifteen!

I checked the other cans in my cabinet. Three listed 20 and two listed 15.

The net weights for all the cans are the same as are the ingredients: green beans, water, salt. Yet the difference between the cans is 17.5 calories, a deviation of 25 percent.

While this discrepancy doesn’t cause me to question what truly is normal the way a house-trashing would, it could cause you to question a bit of advice I’ve dispensed since the inception of this column.

Count calories.

That advice is not really wrong, just really ironic. You definitely do need to count calories if you’re having difficulty achieving or maintaining a healthy weight or want to take your performance in a sport to a higher level.

Just don’t expect to do the task with pinpoint accuracy.

FDA regulations permit food processors to use any one of six methods for determining calories, and all to some degree are estimates. According to Scientific American.com, most employ the Atwater system in which a gram of protein equals 4 calories, a gram of carbohydrates 4, and a gram of fat 9.

Each number, though, is an average.

By using another method of determining calories called bomb calorimetry, researchers know one type of fat can yield as few as 8.4 calories; another, as many as 9.37. Since the average of the types is close to 9.0, the Atwater system uses that number.

But such rounding can lead to rather significant miscalculations.

A study published in the Journal of Nutrition in 2008, for instance, determined that whole almonds have about 20 percent fewer calories than the number used on labels. The fat in whole nuts is poorly assimilated by the digestive system, something the Atwater system can’t account for.

So that one ounce of almonds you eat as your mid-afternoon snack really doesn’t contain the 162 calories printed on the package.

The amount is closer to 129.

I write “closer to” for good reason. Besides the problems with the Atwater system, research shows that people assimilate calories from the same food a bit differently.

In fact, even the way you chew affects calorie assimilation. The more you chew your food, the greater the rate of digestion. More digestion means more calories absorbed.

The same is true for food preparation: the more preparation, the more absorption.

Harvard professors and co-authors Richard Wrangham and Rachael Carmody clarify this in “Why most food labels are wrong about calories,” published by The Conversation in January of 2015. “If you eat a starchy food raw, up to half the starch grains pass through the small intestine entirely undigested ... Even among cooked foods [though], digestibility varies. Starch becomes more resistant to digestion when it is allowed to cool and sit after being cooked, because it crystallizes into structures that digestive enzymes cannot easily break down.

“So stale foods like day-old cooked spaghetti, or cold toast, will give you fewer calories than the same foods eaten piping hot, even though technically they contain the same amount of stored energy.”

To make counting calories even more of a crapshoot, the FDA allows the food processors a 20 percent margin of error. They also require food labels to list the percentage of key nutrients using a 2,000 calorie total - the amount Calorie control.org gives as needed for a moderately active, 132-pound female to maintain her weight.

In a worst-case scenario, a 20 percent margin of error for such a female eating that amount daily creates a caloric surplus of 400. Over the course of a month, that causes an unintentional weight gain of more than 3 pounds.

Despite all the problems with counting calories, though, there is a way to make it work for you. Those details come in next week’s column.