There could be a 150 calorie variance in the amount of energy different people absorb daily from food. (Photo: Getty Images)
Nutrition experts have stressed for years that calorie counting is the best way to maintain a healthy weight. But what if the calories listed on your food labels aren’t accurate?
That’s the assertion made by Geoffrey Livesey, PhD, the head of British nutrition consulting company Independent Nutrition Logic and a nutrition consultant to the United Nations. “The amount of calories a person gets from protein and fiber are overstated,” Livesey told The New York Times on Tuesday.
Livesey has proposed a new system of counting calories that calculates how much energy (i.e. calories) are available in food, as well as what the body can actually use of those calories. With his method, additional calculations are also made to factor in the energy expended by the body during digestion and the degree that food is processed in the body. He has presented his system to the United Nations Food and Agriculture Organization.
But wait: Are calorie counts on food labels really inaccurate? Kind of, says Paul Burghardt, PhD, a professor in the department of nutrition and food science at Wayne State University.
“The ability to measure calories in food is fairly accurate,” he tells Yahoo Health. “The problem is the way we break them down, which varies from individual to individual. On a personal level, it’s not accurate.”
Calorie counts that appear on food labels are currently calculated via the Atwater system. Under the system, scientists put a portion of food in a machine called a calorimeter and burn it to see how much energy it contains. The heat is then absorbed by water. One calorie is equal to the amount of energy required to raise the temperature of one gram of water by one degree Celsius.
Of course, the whole reason we count calories is to try to effectively measure how food will affect our bodies — and that’s where it gets complicated. Accurately measuring calories on a personal level is currently “relatively intensive,” says Burghardt. As of now, it’s typically conducted in a lab setting: Researchers monitor exactly what they’re feeding a person and analyze the subject’s body temperature, as well as the gases they’re breathing in and out. Another method involves analyzing what is consumed and what is produced as waste to get an estimate.
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Why does each person break down calories differently? It’s because of our gut bacteria, says Burghardt: “All of the bacteria that live in our intestinal system has a large impact on how food is broken down and what is absorbed.” He says the type of bacteria in our guts, as well as the proportion of each, can create a 150-calorie difference from person to person in energy absorption each day. That can add up over a week or two. The population of those bacteria can also change based on what we eat, making it especially difficult to effectively calculate what we’ll absorb calorie-wise.
The United States Department of Agriculture also acknowledges that calorie requirements vary per individual, but offers a Daily Food Plan calculator as a way to try to estimate the amount of calories a person should consume based on age, height, sex, and activity level.
As for Livesey’s proposal, Burghardt says it sounds promising, but notes that scalability could be an issue.
So, how can we accurately count calories without entering a lab? Burghardt says the current calorie labeling system is the “best that we’re at right now,” adding that it’s important to be aware of how your body is responding to the food you eat. If you think you’re taking in a certain amount of calories but find that you’re gaining weight, it might be time to adjust your food intake.
But Caroline Apovian, MD, director of nutrition and weight management at Boston Medical Center, says the disparity in calorie counts is more of an issue for researchers and less for the general public. “If this was that big of a deal, we would all be underweight,” she tells Yahoo Health. “Even if our food labels are overestimating the food content, nobody is looking at it.”
Apovian says she hopes people won’t take this information and use it as an excuse to consume even more calories. “It’s not the fault of people measuring calories that we’re eating unhealthy,” she says.
While Burghardt is hopeful that future calorie counts will be more accurate, he agrees that overstated calorie counts aren’t terrible: “If we’re in a situation where we’re overestimating calorie counts and absorbing less, that would probably be for the best. We’re not undernourished as a collective group right now.”