Fast food is a common meal option, but it’s high in calories and low in nutrients. Eating too much of it could affect nearly all parts of your body.

Swinging through the drive-thru or hopping into your favorite fast food restaurant may happen more often than some of us would like to admit.

Between 2013 and 2016, 36.6% of U.S. adults ate fast food on a given day. The amount was nearly the same for children and adolescents, with 36.3% of them eating fast food on a given day during 2015 to 2018.

While an occasional fast food meal won’t hurt, a habit of eating out could be doing a number on your health. Read on to learn the effects of fast food on your body.

Most fast food, including drinks and sides, are loaded with carbohydrates with little to no fiber.

When your digestive system breaks down these foods, the carbs are released as glucose (sugar) into your bloodstream. As a result, your blood sugar increases.

Your pancreas responds to the surge in glucose by releasing insulin. Insulin transports sugar throughout your body to cells that need it for energy. As your body uses or stores the sugar, your blood sugar returns to normal.

This blood sugar process is highly regulated by your body. As long as you’re healthy, your organs can usually handle these sugar spikes.

But frequently eating high amounts of carbs can lead to repeated spikes in your blood sugar.

Over time, these insulin spikes may cause your body’s normal insulin response to falter. This increases your risk of insulin resistance, type 2 diabetes, and weight gain.

Sugar and fat

Many fast food meals have added sugar. That means extra calories without added nutrition. The American Heart Association, which referred to people as either men or women, suggests only eating about 100 calories or 6 teaspoons of added sugar per day for women or 150 calories or 9 teaspoons for men.

Many fast food drinks alone contain more than the daily recommended amount of sugar. A 12-ounce can of Coca-Cola contains 9.75 teaspoons of sugar. That equals 140 calories, 39 grams of sugar, and no other nutrients.

Another common fast food ingredient, trans fat, is manufactured fat created during food processing. It’s commonly found in:

  • fried pies
  • pastries
  • pizza dough
  • crackers
  • cookies

No amount of trans fat is good or healthy. Eating foods that contain it can increase your LDL (bad cholesterol), lower your HDL (good cholesterol), and increase your risk of type 2 diabetes and heart disease.


The combination of fat, sugar, and lots of sodium (salt) can make fast food tastier to some people. But diets high in sodium can lead to water retention, which is why you may feel puffy, bloated, or swollen after eating fast food.

A diet high in sodium is also dangerous for people with blood pressure conditions. Sodium can elevate blood pressure and put stress on your heart and cardiovascular system.

One study found that about 90% of adults underestimated how much sodium was in their fast food meals.

The study surveyed 993 adults and found that their guesses were lower than the actual sodium content by more than 1,000 mg.

Keep in mind that the Food and Drug Administration (FDA) recommends adults eat no more than 2,300 milligrams of sodium per day. More than 70% of sodium comes from processed foods and restaurant meals.

Excess calories from fast food meals can cause weight gain. This may lead toward obesity.

Obesity increases your risk of respiratory problems, including asthma and shortness of breath.

The extra pounds can put pressure on your heart and lungs, and symptoms may show up even with little exertion. You may notice difficulty breathing when you’re walking, climbing stairs, or exercising.

Restaurants may increase the challenge of calorie counting. Research indicates that people often inaccurately estimate the number of calories of menu items.

Your central nervous system consists of your brain and spinal cord. These areas of your body may also see an impact from eating fast food.

One study from 2020 found that among college students, eating higher amounts of fast food (and, interestingly, salad) was linked to a lower short-term memory score.

Still, other research from 2019 found no effect of fast food consumption on cognitive function. More studies are needed in this area.

The ingredients in junk food and fast food may have an impact on your fertility.

One study found that processed food contains phthalates. Phthalates are chemicals that can interrupt how hormones act in your body. Exposure to high levels of these chemicals could lead to reproductive issues, including developmental issues for a fetus.

The foods you eat may impact your skin’s appearance.

A research review from 2021 found that dairy, chocolate, foods high in fat, and foods with a high glycemic index (carbohydrates and sugar) were associated with acne, though more studies need to be done. These foods are often present in fast food.

On the other hand, the research suggested that eating fruits, vegetables, and fatty acids (found in fish and olive oil) helped protect against acne.

Carbs and sugar in fast food and processed food can increase acids in your mouth. These acids can break down tooth enamel. As your tooth enamel disappears, bacteria can take hold, and cavities may develop.

Obesity can also lead to complications with your bone density and muscle mass. People with obesity may have lowered bone quality and a higher risk of breaking bones, especially among older adults.

It’s important to keep exercising to build muscles, which support your bones, and keep up a healthy diet to minimize bone loss.

Eating fast food may affect your mental health along with your physical health.

A 2020 study found that consuming fast foods with sugary drinks increased the chance of mental health issues in middle school students in China.

Research from 2018 also suggested that eating a Western diet high in red meat, takeout, and refined foods was linked to a higher body mass index (BMI) and inflammation in 14-year-old participants. This was then associated with depressive symptoms and mental health issues when they were 17 years old.

Today, more than two in five U.S. adults and around one in five children have obesity.

Offerings at fast food restaurants may be contributing. One study found that between 1986 and 2016, portion sizes and the number of calories in restaurant entrées and desserts increased significantly.

As Americans eat out more frequently, it could have adverse effects for both individuals and America’s healthcare system.

What are the health risks of eating fast food?

Fast food is often high in calories, fat, and sugar but low in nutrients and fiber. While eating fast food occasionally isn’t a problem, consuming it frequently may raise your risk of obesity, heart attack, and other health issues.

What happens if you eat fast food more than two times a week?

Eating fast food too often may negatively affect your health. An older study from 2012 found that Chinese Singaporean adults who ate Western-style fast food at least twice per week had a higher risk of developing type 2 diabetes and dying from coronary heart disease compared with adults who consumed little or no fast food.

Fast food is a popular choice for its taste and convenience, but it tends to be high in calories, sugar, and fat and low in nutrients.

Eating fast food frequently may negatively affect multiple areas of your body, possibly increasing your risk of conditions including type 2 diabetes, obesity, and high blood pressure. As a result, it’s best for your health to eat it only occasionally.