Why You Shouldn’t Measure Exercise Hours in Slices of Cheesecake

Health and medicine explained.
Aug. 4 2014 3:44 PM

Calorie Miscounting

Why one slice of cheesecake does not equal 4½ hours of aerobics.

The Cheesecake Factory’s Reese’s Peanut Butter Chocolate Cake Cheesecake.
The Center for Science in the Public Interest dubbed Cheesecake Factory’s Reese’s Peanut Butter Chocolate Cake Cheesecake ”Reese’s Obeses” in its annual Xtreme Eating awards.

Photo by Dominick Reuter/Reuters

The Center for Science in the Public Interest, a food-focused consumer advocacy group that aims “to provide consumers with current, useful information about their health and well-being,” inaugurated its annual Xtreme Eating awards in 2007. The sardonic awards call out a handful of chain restaurant menu items that are particularly high in calories, saturated fat, sugar, or sodium. This year’s roster, released last week, includes the Cheesecake Factory’s 2,780-calorie Bruléed French Toast, Famous Dave’s 2,770-calorie St. Louis-Style Spareribs, and Chevys Fresh Mex’s 1,920-calorie Super Cinco Combo.

L.V. Anderson L.V. Anderson

L.V. Anderson is a Slate assistant editor. She edits Slate's food and drink sections and writes Brow Beat's recipe column, You're Doing It Wrong. 

The CSPI’s goal seems to be to shame restaurants that offer outrageous portion sizes that risk customers’ health. There’s nothing wrong with this type of public shaming, although you might argue that its utility to consumers is minimal: While portion creep is a real problem, most of us aren’t ordering 2,780-calorie breakfasts every day (or even every week). From a consumer’s perspective, the main appeal of the awards seems to be entertainment value: There’s schadenfreude-tinged fun to be had in gawking at the ridiculous products marketers try to foist on us.

But entertainment value doesn’t excuse some of the awards’ questionable tactics. The list focuses on the meals’ potential effect on your waistline in a way that seems to shame people who eat at the Cheesecake Factory rather than restaurant executives. (A pizza is described as “a fresh layer of deep belly fat”; a slice of peanut butter cheesecake is dubbed “Reese’s Obeses.”) But that’s a matter of style—even worse is the factually inaccurate way CSPI equates each meal to a certain number of hours of a certain exercise. That French toast is equated to seven hours of lap swimming; a Red Robin combo meal equals “a 12-hour brisk walk.” After eating that peanut butter cheesecake, according to CSPI, “To turn the calorie clock back to zero, you’d have to do aerobics for 4½ hours.”

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These statements, a new feature of this year’s awards, are thoroughly misleading. Granted, equating junk foods with exercise times is a common tactic on clickbait-y health websites, but a nonprofit that claims to provide useful health information to the public should really know better.

One problem with equating a slice of cheesecake to 4½ hours of aerobics is obvious if you think about the human metabolism: How many calories you burn doing 4½ hours of aerobics depends on your weight, age, gender, and fitness, among other factors. There’s also the question of how hard you’re exerting yourself during those 4½ hours of aerobics—are we talking half-hearted jumping jacks or a fast-paced step routine that makes it hard to catch your breath? Most activity calorie calculators you can find online (or embedded in exercise machines) ask you to enter your weight at the very least, but even the ones that also ask for your gender, age, and height aren’t perfect. The only accurate way to find out how many calories you’re burning doing aerobics is to visit a physiology laboratory that can measure how much heat your body produces or how much oxygen you consume while working out.

So to say that a 1,500-calorie slice of cheesecake requires 4½ hours of aerobics penance is misleading and gives a false sense of precision. The amount of calories burned during aerobics depends entirely on who is doing the aerobics.

That’s not the only reason CSPI’s equation of a platter of junk food with a strenuous workout is wrong. Human bodies aren’t like cars that burn energy only when they’re running and don’t burn any energy when they’re inactive. To the contrary, most of the calories we burn in any given day are expended while we’re not exercising. Breathing, firing neurons, circulating blood, repairing cells, and other unconscious physiological processes require calories—and these bodily functions account for your basal metabolic rate. Like calories burned during exercise, your basal metabolic rate depends on your gender, weight, fitness, etc., and therefore rates vary widely across the population. Most adults’ basal metabolic rates fall between 1,000 and 2,000 calories per day. This means that if you eat a 1,500-calorie slice of cheesecake, you don’t need to do 4½ hours of aerobics to burn it off—if you just do nothing for the next day or so, your body will use all those calories.

Equating X food with Y hours of exercise is tempting because it’s a simple, clear way of describing the caloric content of food. But in this case, simplicity is deceiving. Human bodies aren’t machines—scientists are still discovering new ways that our microbiome, diet, and hormones affect our metabolism. It’s comforting to think that anyone can “neutralize” the calories in a plate of French toast, as CSPI puts it, by timing their workout down to the minute, but this false equivalence obscures the complexity of the human body. The Center for Science in the Public Interest should stop spreading deceptions that are neither based on science nor in the public’s interest.

L.V. Anderson is a Slate assistant editor. She edits Slate's food and drink sections and writes Brow Beat's recipe column, You're Doing It Wrong. 

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