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Can Calorie Counts on Food Labels Be Trusted?

  • by
  • March 3, 2013
  • 10:00 am
Can Calorie Counts on Food Labels Be Trusted?

In many cases, no, calorie counts on food labels cannot be trusted, and for more reasons than one.

In this New York Times Op-Doc, filmmaker Casey Neistat shows just how unreliable they can be. Enlisting the services of a science lab equipped with a calorimeter, he tested five random samples selected from among foods he might eat on any given day. Four of those five had more calories than their labels said they did, including a pre-packaged spicy tofu sandwich that had nearly double the amount. A Subway sandwich was the only one that came in under the stated calorie count.

Some scientists are also questioning the very system we use for measuring calories in foods, the century-old Atwater system that assigns 4 calories per gram for proteins and carbohydrates and 9 calories per gram for fats. That system does not take into the account the fact that the degree to which our bodies metabolize foods varies with the type of food, the level of processing it has undergone and the “energy status” of the person eating it.

For example, some of the fat in almonds and certain other nuts goes undigested and passes through our bodies as waste. A 2012 study led by USDA scientist Janet Novotny found that the calories we get from a one-ounce serving of almonds is 32 percent less than the Atwater values estimate. So when you eat a large handful of almonds, you may only be taking in 109 calories as opposed to the 161 calories listed on the label. As NPR reports, scientists suspect that this is because we don’t chew them enough to fracture all the cell walls and release all the fats.

Food processing also affects the number of calories we actually absorb from a food. Rachel Carmody, a postdoc at Harvard University who organized a symposium called “Why a Calorie Is Not a Calorie and Why It Matters for Human Diets” at the American Association for the Advancement of Science’s annual meeting last month, told NPR that she wants people to “realize that something that’s more highly processed is going to represent more calories than in a less-processed form.”

Based on experiments conducted in her lab, she attributes the net energy gains “to higher rates of nutrient assimilation in the small intestine as well as reduced diet-induced thermogenesis, the metabolic cost of digestion.” It is a lot easier for our bodies to extract nutrients and calories from cooked and processed foods than from whole and raw foods, and those foods also require less energy for our bodies to digest.

These aspects of digestion are not represented in the Atwater factors typically used in the determination of metabolizable energy value. Thus researchers who report Atwater-based energy values as well as consumers who utilize nutrition labels to manage their caloric intake will necessarily underestimate the energetic gains associated with a processed diet.

Still, other experts like Malden Nesheim and Marion Nestle, co-authors of “Why Calories Count,” argue that “for most foods, estimates based on Atwater values are close enough.” And “until research convinces us otherwise, we believe a calorie is a calorie.”

An awareness of the calorie content in foods is supposed to help us make more informed choices and perhaps cut back a bit on what we eat. That’s the point of the new federal requirement that calories be posted at food establishments across the country, which is expected to go into effect at some point this year. We’ll have to wait and see whether or not across-the-board calorie labeling will help Americans lose weight or improve health outcomes. But if it’s going to do any good, as suggested in the Op-Doc, don’t we at least have to start with calorie counts that are a little more reliable?

 

Related Stories:

All Calories (and All Foods) Are Not Created Equal

Calorie Labeling on Menus May Not Change Eating Habits

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154 comments

+ add your own
11:41AM PDT on Mar 18, 2013

I doubt it .... I just look at the label for an approximation and compare products.

9:30AM PDT on Mar 18, 2013

A calorie is not a calorie. And I've never trusted packaged food to be entirely honest. I just try to avoid as many carbs as I can and I've recently started eating almost no sugar. That eliminates most of what I really shouldn't be eating, I think.

4:29AM PDT on Mar 12, 2013

Presumably the present system is useful for comparing different foods, or today's intake with yesterdays? The manufacturer can't be responsible for how we cook it, mince it or chew it.
Most people are ignorant about all this, so it is best to keep labelling simple.
Making judgments from trial of five samples, paid for by a film maker is hardly worthy of discussion.

11:39AM PDT on Mar 10, 2013

Thanks

6:33AM PDT on Mar 10, 2013

thanks

5:11AM PDT on Mar 10, 2013

thank you

6:47PM PST on Mar 7, 2013

NO!

11:44AM PST on Mar 7, 2013

I always wondered about this. But I have a problem with changing how we count calories. With the obesity crisis, I don't think lowering the amount of calories actually absorbed would help at all. I imagine that varies from person to person.

10:41AM PST on Mar 7, 2013

I usually just eat until I'm full.

7:46AM PST on Mar 7, 2013

Norman J is right - we are not bomb calorimeters. Those things burn EVERYTHING that can be burned, and measure the released heat, i.e. energy. So, for example fiber, a form of carbohydrate, from which we cannot extract energy, or calories, does burn in a calorimeter, and the energy released from it is included in the calorie count of the food. You could package a birch log in a food wrapper, and according to the calorimeter, you'd get that about 4 kcal per gram (of dry wood, excluding all water!). You try and eat it, all you get is splinters in your mouth. I am not sure how exactly the food producers are expected to report and label these products, given that different kinds of carbs really do have different amounts of energy that is bioavailable to humans. Taking into account that different people take up energy at different efficiencies (we all know those annoying people who can seemingly eat anything as much as they'd like and not gain any weight), the calorie count in the labels can only be an approximation of what we can actually take from them. I wonder if they analyzed anything else, like fats, carbs (different kinds, please!), proteins etc.

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