20 Things That Happen to Your Body When You Eat Fast Food

by Grant Stoddard

Fast food. It’s cheap, convenient and marketed to us when we’re young, in the hope that we’ll be consumers for life. For many companies, that strategy has paid off. But there’s a wrinkle in that math. If we eat too much of this stuff, that frequent consumer’s lifespan could be a lot shorter than if he’d eaten more food unassociated with clowns, colonels, kings and freckle-faced girls with red pigtails.

See, in many cases, fast food is highly processed and contains large amounts of carbohydrates, added sugar, unhealthy fats and sodium. These foods are almost always high in calories while offering little in the way of nutrition. And when fast food frequently replaces nutritious whole foods in your diet, it can lead to all sorts of bad health outcomes. Derailing your weight loss goals is just one. Here are 20 things you can expect a fast-food diet to do to your body in a relatively short amount of time.

1. You’ll increase your obesity risk

If you switch from a balanced diet of whole foods to one of fast food, the most obvious difference you’d register would be the enormous uptick in (largely empty) calories you’d consume per meal. Hello, belly fat — and worse: “The high calorie intake can lead to obesity, which puts you at risk for developing chronic diseases,” warns Jim White, RD, ACSM, owner of Jim White Fitness&Nutrition Studios.

2. But you’ll also starve

…nutritionally speaking. The high calories in fast food are accompanied by low nutritional content. Too much of that, and your body will begin to lack the necessary nutrients it needs to function properly. “Your body is temporarily full with empty foods that don’t provide nourishment, so even though you may have eaten a lot of calories, you won’t be satisfied for long,” says Amy Shapiro, MS, RD, CDN, founder of Real Nutrition NYC. For 150+ ideas for delicious foods that will slim your waist without sacrificing flavor, check out the best-selling Zero Belly Cookbook — test panelists lost 16 pounds in 14 days!

3. You'll increase your cancer risk

PhIP is short for 2-Amino-1-methyl-6-phenylimidazo(4,5-b)pyridine. According to the Physicians Committee for Responsible Medicine, this catchy-sounding chemical appears in the grilled chicken marketed by a major fast-food chain. “The organization says the substance, which forms when meat is heated to a certain temperature, is associated with human breast, prostate and colon cancers,” says Seth Santoro of LA Life Chef.

4. You’ll heighten your risk of heart disease

Fats commonly found in fast food are made up of saturated fatty acids. Those are fats that are solid at room temperature, often derived from animals and some plant oils. You’ll find it abundant in, say, a cheeseburger. Jim White warns that these fats can raise the blood cholesterol levels, which leads to an increased risk of cardiovascular disease. So kick your fast-food habit and stock up on these 10 Foods That Make Your Heart Younger!

5. Memory and cognitive function will decline

Fast foods like bacon burgers, some fried foods and milkshakes can be high in saturated fats. “It’s been long established that saturated fats can negatively impact the heart, but there’s also research that suggests high saturated fat intake may negatively impact brain function and memory,” says Marisa Moore, MBA, RDN, LD. She adds that higher intakes of saturated fatty acids may impair memory speed and flexibility and prospective memory (your ability to remember to do what you intended). You intended not to pull into the drive-thru, remember?

6. You’ll be constipated

Dietary fiber (commonly found in vegetables, fruits, whole grains, nuts and seeds) plays a dominant role in the digestive system. Fiber helps keep your digestive tract working properly as it ushers wastes out of the body. It can help lower cholesterol and keep blood-sugar levels normal. “Unfortunately, most fast foods don’t contain high dietary fiber contents,” says White. What does? These 11 Best High-Fiber Foods for Weight Loss!

7. Your skin will deteriorate

Eating fast food may cause skin issues such as acne. “No, it isn’t the chocolate or fried components,” says Shapiro. “It’s the simple sugars, white flour and empty carbs like French fries that can be blamed.” Fast food is a definite Not That! when it comes to What to Eat for Better Skin!

8. You’ll bloat

Some foods naturally contain higher amounts of sodium, but sodium is also added to many food products. Some of these additives are monosodium glutamate (MSG), sodium nitrite, sodium saccharin, baking soda (sodium bicarbonate), and sodium benzoate, which are used as flavoring or preservatives. Regarding dietary sodium limits, it’s suggested that adults stay under 1,500 mg per day, and should never consume more than 2,300 mg/day. Santoro says a single fast food meal can actually exceed 2,300 mg. “Too much sodium causes your body to retain water, making you feel bloated and puffy,” he adds. “But that’s the least of the damage overly salted foods can do.”

9. Your kidneys and stomach
will suffer

Sodium also can contribute to existing high blood pressure or an enlarged heart muscle. If you have congestive heart failure, cirrhosis, or kidney disease, too much salt can contribute to a dangerous buildup of fluid. “Excess sodium may also increase your risk for kidney stones, kidney disease, and stomach cancer,” says Santoro.

10. Your teeth will decay

Frequent soda intake can lead to poor oral health, says Leah Kaufman, MS, RD, CDN. Drinking large amounts of soda increases the amount of acid in your mouth, which eventually causes tooth decay and cavities. “Some of your fast food desserts, such as McFlurries or Frosty, may also add to this,” she says. And that’s not all. Check out our report on What Happens To Your Body When You Give Up Soda!

11. Your mental health could decline

Recent research shows that eating fast food may cause a higher rate of depression, Shapiro says. One study indicated that people who ate fast food were 51 percent more likely to develop depression that those who didn’t.

12. Your blood sugar will spike

Eating high-carb fast food increases your blood sugar. As you consume white-flour-based foods — such as the bun from a burger, or French fries with your sandwich — your body takes in a large amount of white sugar. “Frequent consumption of these foods may lead to diseases such as obesity — which the American Medical Association has indicated is a clinical diagnosis — and diabetes,” says Kaufman.

13. You'll worry more

There's a lack of omega-3 fatty acids in fast foods. Shocker! A dearth of those good fats can create a more anxious mental state. But it’s not just what fast food lacks that can cause anxiety. This stuff is also high in refined carbohydrates, which can lead to fluctuations in blood sugar. If your blood sugar dips into hypoglycemic levels, you can experience anxiety, trembling, confusion and fatigue.

14. You could end up with liver disease

PAPs stands for “polyfluoroalkyl phosphate esters,” chemicals that line fast-food packaging to make it grease- and waterproof. “The substances leach to the food inside the packaging and end up in your bloodstream. They’re linked to liver disease as well as cancer,” says Santoro.

15. Your cholesterol could skyrocket

Many fast foods served are derived from animal products, deep fried and served with cheese and high-fat dipping sauces. “The high fat content in fast food can contribute to high cholesterol, which can also lead to atherosclerosis. That occurs when plaque builds up in the arteries and prevents the flow of blood to the heart and organs,” says White. What’s more, fast food can lower your good (LDL) cholesterol, further putting your heart and your health on the line. Make sure you practice these 9 Ways to Lower Your Cholesterol in 5 Seconds!

16. Your risk of cancer continues
to grow

Sodium nitrate and sodium nitrite are additives used to maintain meat color and to inhibit bacterial growth. “Both chemicals can break down into nitrosamines, substances with the potential to cause cancer,’” says Santoro.

17. Your bones could weaken

As we mentioned, fast food is typically loaded with sodium. One Big Mac has 970 mg of sodium, well over one-third of the daily recommended allowance. A high sodium intake can cause your bones to weaken, leading to possible osteoporosis, Shapiro warns.

18. Food dyes could color
you sick

A study by the National Toxicology Program of the U.S. Department of Health and Human Services says 2-methylimidazole causes cancer in lab rats. That’s bad because 2-methylimidazole is an ingredient in caramel coloring which is used in most dark-colored sauces and sodas. It gets worse. Another of this coloring agent’s ingredients is 4-methylimidazole. Researchers tested the effects of 4-methylimidazole on lab rats and mice and concluded that there was “clear evidence of carcinogenic activity of 4-methylimidazole in male and female B6C3F mice.”

19. You’ll be lethargic...

With large portions that are often high in fat, fast foods like burgers, fries and milkshakes, fast food often delivers a hefty dose of calories. “Those large portions often leave you feeling full and lethargic,” says Marisa Moore.

20. ...or hyper

Anxiety and depression aren't the only mental effects that fast food can induce. Eating a diet high in artificial colors and preservatives may play a role, as well. A review of related research published in the journal Clinical Pediatrics indicates that many artificial colorings, along with the preservative sodium benzoate, increase hyperactivity. The bottom line: Skip the Golden Arches, stay at home and make The Best-Ever Burger For Weight Loss!


The 55 Best Ways to Boost Your Metabolism

50 Weight Loss Secrets From Slim People

Every Menu Item at McDonald’s—Ranked!

40 Bad Habits That Give You Belly Fat


FOR 150+ recipes that flatten your belly fast—made with the foods you love—buy the brand-new book from Abs Diet creator David Zinczenko that's already topping the Amazon charts: Zero Belly Cookbook!

Zero Belly Cookbook
Zero Belly Cookbook