Here’s What Happens to Your Body if You Eat Fast Food Once a Week

Fast food. It's there. It's convenient, especially if you're traveling or constantly on the go (and starving). You've also likely heard of the downside. In the most severe cases, eating processed and fast food may kill more people than smoking.

Still, data consistently shows that Americans eat fast food...consistently. As in, every day.

According to 2018 data collected by the CDC, one in three Americans eat fast food every day. More recent data from Drive Research published in 2023 was a bit more promising, though it noted that 20% of men consumed fast food daily compared to 7% of women, but nearly 2 in 3 people reported consuming it at least once per week.

So, what if you're also someone who eats fast food semi-regularly? Like once a week, for example? We asked registered dietitians—here's what they had to say.

What Happens to Your Body if You Eat Fast Food Once a Week

If you dabble in fast food once a week or so—say, a stop at the McDonald's drive-thru after a busy day at work—Ana Reisdorf, MS, RD, says the health impact will depend on the individual. "For most healthy people, if you eat well and are physically active, eating fast food one time per week likely won't have much impact, particularly if you manage your portions and make better choices at other meals," she explains. "If you have a health condition, such as diabetes, high blood pressure or kidney disease, however, the sodium and sugar content of many fast food meals may not be the best choice to eat weekly."

Cesar Sauza, RD, a registered dietitian, agrees. "Eating fast food once a week should not affect anyone as long as they have a balanced diet rich in whole foods besides that one time," he says. "Fast food should be limited as much as possible but one time a week is usually the recommendation since many people are eating fast-food at least three times per week."

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What if You Eat Fast Food Every Day?

If you up your consumption to daily, the story changes a bit. "Fast food is usually high in calories, fat, sodium, sugar or all of the above; it is possible to eat healthier at fast-food restaurants but fast-food restaurants are never the places to eat while trying to be healthier," Sauza says. "Years of daily fast-food consumption will lead to excess weight and fat gain and increased risk of chronic diseases like diabetes and heart disease."

Reisdorf also notes that it is possible to make healthier choices at fast food restaurants. "The health consequences will likely depend on what you order," she says. "A regular-size hamburger with no fries or soda is a relatively balanced meal. If you paired that with a healthy high-fiber/high-protein breakfast and dinner, you can probably keep your calorie, fat and sugar intake under control."

Related: Here's Exactly What Happens to Your Body if You Eat Spinach Every Day

That being said, Reisdorf adds, most people who eat fast food typically opt for the fries and soda. "This type of meal can easily top 1000 calories or more. Over time, eating fast food often will lead to an increased risk of obesity, high cholesterol, high blood pressure and possibly malnutrition."

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How To Make Your Fast Food Order Healthier

As Reisdorf noted, skipping the fries and soda is a great way to make your fast food order healthier. And in general, her top tip for eating healthier at fast food restaurants is to watch portion size. "I would recommend starting with keeping portion sizes under control," she says. "Order a medium or small for your fries and stick with water or unsweetened tea as a beverage. Avoid double or triple hamburgers. Check out salad options (which sometimes are also high in calories), which may provide better alternatives."

Sauza says that if it's possible to skip fried foods, you should try to do so. "Fried foods should be thought of as sponges that absorb fat," he says. "A fried food will always have a lot more fat than if it wasn’t fried. Skip the fries when eating fast food or choose the smallest serving. Remember, potatoes do not contain fat—but frying them loads them up with oil changes the story."

Sauza also suggests skipping the soda. "Soda and fast food are always connected, but it should be what is most avoided when eating out," he says. "Fast food has enough calories on its own without the sugary drink."

Long story short: It's probably not a good idea to eat fast food every day. But if you eat it once a week—or better yet, twice a month!—you're probably fine. Just make sure the rest of your diet is healthy and balanced.

Next up: What Dietitians Order At McDonald's