Should You Count Calories?

So, should you count calories?

It depends who you are. People who are fairly fit and close to where they want to be often don’t need to count calories. People who are far overweight usually have no idea what they eat, typically misreporting eating by about 800 calories a day! Here, a food diary works well. For the underweight, counting calories is a good way to remind yourself to eat more.

It’s so common that we don’t notice it - every diet plan or weight loss method talks calories. Ever time you see a slimming or healthy meal plan or recipe, calories get a mention - and sometimes they seem to be so accurate that they couldn’t possibly be right. How can you say your slice of carrot cake has 406 calories? That would have to be accurate to the crumb.

In fact, how accurate is calorie counting generally?

Not very.

In many cases, the caloric content of food is assessed in a laboratory. Calories are energy expressed as heat - a calorie is a unit of heat energy, the amount of energy required to raise the temperature of a kilogram of water by one degree Celsius. Foods are rarely simply burned nowadays to find out how many calories they contain. Instead, they’re frozen in liquid nitrogen and ground to a fine powder. Experiments are performed on this powder to reveal caloric content, fat content, protein content and so forth. But while these are often chemical experiments they use a table of results that was devised in the nineteenth century by a chemist, Wilbur O. Atwater, who really did just burn things to measure the heat they gave off, in a machine he called a ‘bomb calorimeter.

So when you read the number of calories in food you’re buying, just remember it was worked out by people in the lab referring to the data of a man whose life’s work was trying to boil water with hamburgers.

Is it possible that the amount of calories we think is in our food is wrong?

No. It’s almost certain.

Not everything burns in the same way or the same rate, and while the reactions inside the human body that turn our food into energy are exothermic oxidising reactions - literally burning - the job isn’t all done in great big fire in your belly. The amount lost in heat differs wildly from macronutrient to macronutrient, by a margin of about 25%, for one thing.

See Also: Are You Wasting Your Time Counting Calories?

It’s now time to be fair to Wilbur Atwater: he foresaw this problem and did some of his experiments measuring the energy output of an active person who ate the foods he was testing, but the results are still unreliable.

So the calories you’re counting are wrong anyway.

Then there’s the way nutrients are used in your body.

So the calories you count aren’t just wrong - they’re wrong twice. Add in genetic differences and differences in basal metabolism, and that 406-calorie slice of carrot cake starts to look less like scientific prescription for weight loss and more like a number that was just pulled out of the air.

Finally, the real clincher is that even people who keep food diaries and are being assessed by professionals who actually watch what they eat misreport what they eat. Most people misreport by about 350 calories a day, but obese people misreport by about 800 calories a day. So even if calories were simple - which they’re not - and accurate - which they’re not - we don’t seem to be able to use them anyway!

So calorie counting doesn’t work.

But does that mean we need to get better at it, or find a different way to work out weight loss plans?

If we got better at knowing exactly how many calories were in our food, we’d also need to include bioavailability indexes so we’d know if we’d be able to assimilate the full amount, and we’d need to include indexes that showed us how the different macronutrients would interact with our specific genetics and lifestyle too. So unless you’re a research nutritionist, this isn’t really an option - and most people lack the background, education and interest to make use of that information even if it were presented to them. For most of us, it’s a non-starter.

So how should we be figuring out what we’re eating?

Here’s where the picture gets hazy. If you’re close to the weight you want to be and your concern is performance the calorie counting to the nearest, say, 250 a day might woe for you. The story’s the same if you’re working on body composition goals but they’re pretty close. If you’re dropping the last 10 pounds, then counting calories to the nearest 250 a day and using foods’ calorie labels to learn to tell high-energy, low-nutrition junk food from the food that’s going to keep you well and full all day can be effective.

Similarly, if you’re a lighter person, especially a young man, and you’re trying to put on weight, the chances are that you misreport in the wrong direction - that you incorrectly believe that you eat way more than you really do. Counting calories can have some utility for people in this situation too.

That doesn’t come from counting calories alone. It comes from an understanding of how calorifically dense a certain food is, what else it can do for you and how much of it you plan to have.