So you ate more Ben and Jerry’s than you should have. But, hey, you’re going running later, so you should be fine — right?
There is no shortage of online charts and even government-endorsed digital dieting tools that will instruct you in this way of thinking. Some dietitians and nutritionists even do it. The concept fits in neatly with contemporary nutrition culture, with its simple mathematical mantra of “calories in, calories out.”
“There is probably a large part of the healthy population that this works for, but it doesn’t work for enough people that we can say, ‘This is how it works,’ ” said dietitian Ashley Koff.
These types of tools aren’t wrong, exactly, she said. “They could be right for a certain group of people. But what it’s doing is oversimplifying how one gets and keeps a healthy weight loss.”
The calculator below illustrates how such estimates come about, using a set formula to calculate how much activity may be required to burn the calories in a food item. But it and other tools like it assume that there are no problems with calories in, calories out. The calculator was devised by Graphiq and uses data from the ESHA nutrition database.
Most nutritionists also simplify things. What are dieters supposed to do if their only caloric model doesn’t always work?
Koff is right there with you. “My biggest frustration is that nobody’s saying the same thing,” she said.
How exercise works
Part of this comes down to how bodies and metabolisms vary. Factors such as gender, current weight and body composition all influence how many calories a person burns with any one activity.
Men, who tend to have more muscle, burn more calories than women. People who are very overweight or obese may burn calories at a higher rate. Even among exercisers in the same age range, differences in calorie burning abound, said Kristin Kirkpatrick, a dietitian at the respected Cleveland Clinic.
That means a chart saying that 36 minutes of yoga will negate a bag of Lay’s chips doesn’t reflect how any one individual body works. Same goes for a Zumba poster claiming a single class will burn 1,000 calories.
“If you take seven different people of different ages, genders and body size, put them all in a line and tell them to run three miles, they’re all going to burn different amounts of calories,” Kirkpatrick explained.
Those calorie numbers aren’t always wrong, but they do fall within a range, so there’s no guarantee every person looking at that number is actually meeting it with his or her exercise regimen.
Then there’s the exercise itself, which differs in intensity and quality. Intense interval training is different from time spent texting on the elliptical, for example.
Plus history factors into how individual bodies interact with exercise. If you’ve been doing the same gym routine for a long time, it’ll put less stress on your body and thus won’t result in the same heightened metabolic level.
“Your weight loss is multifactorial; it’s not just your calories. There is a particular thing that works for your body, and that’s going to be a factor,” Koff said.
So, contrary to all those charts, you can’t quite exercise additional calories away.
In fact, people often overestimate how much they’ve burned off during exercise, Kirkpatrick and others said, and then overeat as a result — and causing weight gain.
What calories consist of
So are these kinds of calories-to-exercise calculations useless? They can be helpful to understand what food contains and how it’s supposed to be used, or as an energy source, experts said.
But even if a person could be sure they were burning off their indulgences, it shouldn’t be used — as Kirkpatrick puts it — as “almost like a way to game the system.”
Besides being a unit of energy, a calorie also affects how hungry a person will be later, as well as their ability to lose or maintain their weight. Calorie quality also helps refuel the body after that exercise, and influences a person’s energy level moving forward, said Maria Elena Rodriguez, a dietitian at the Mount Sinai Health System.
Exercise won’t reverse the other aspects of that pint of ice cream: the way it affects the liver, for example, or the large amount of sugar going into the body.
“We need to teach people to eat better, not to game the system to eat foods … [thinking] they can just walk the calories off later,” Kirkpatrick said.
Still, this is hardly the clarion call for calorie extinction. “We still need to look at calories in some ways,” Kirkpatrick said.
There is “some truth” to calories in, calories out, with calories still making a difference on a basic level, she said, though the model doesn’t account for significant differences in how people burn calories and in the calories themselves.
But it is time to retire your spin-to-supper calculations.
“If you have a cookie, then run 3 miles, is that really enjoying your cookie? Sit down and enjoy it. Have it be real.”