While it's possible to make healthier choices at fast-food restaurants, eating fast food every day or very often can have negative effects on your health, like promoting weight gain and chronic disease. It's partly about what's in your fast food — but also about what's not in your fast food.
When eating at fast-food restaurants, opt for choices that are lower in calories, fat and sugar.
Potential Negative Effects of Fast Food
The appeal of fast food is right there in its name: Menu items at these restaurants are intended to be mass-produced quickly. But, fast production doesn't usually include nutritious ingredients or cooking processes. "Traditional fast food (burgers, fried chicken, fries and the like) tends to be high in sodium, saturated fat and sugar because those ingredients make foods taste better to most people," says Anne Danahy, RD, a dietitian based in Scottsdale, Arizona.
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Besides adding sodium, sugar and fat to your diet, some of the negative effects of fast food have to do with nutrients you're not getting when you eat it. Often, fast food restaurants have limited options for fresh fruits and vegetables, whole grains and lean proteins that provide healthy fats, unrefined carbohydrates and important micronutrients, notes a June 2013 study in the American Journal of Preventive Medicine.
Iceberg lettuce, for example, which is used in many fast food salads, contains significantly less fiber, iron and calcium than a leafy, green alternative like spinach, per the U.S. Department of Agriculture.
The good news is that the negative effects of fast food have gotten some attention from experts and researchers.
Fast Food and Weight Control
If you're watching your weight, eating fast food every day may not be ideal. According to the Centers for Disease Control and Prevention (CDC), eating fast food every day or very frequently has been shown to contribute to weight gain with a pretty clear correlation: As the percentage of total daily calories from fast food increases, weight status increases, too.
Portion sizes are partly to blame. Researchers have found that portion sizes and total calories at fast-food restaurants have steadily increased since 1986, according to one June 2019 study in the Journal of the Academy of Nutrition and Dietetics. And "larger-than-appropriate" portions increased the risk of putting on weight, according to a November 2014 study in Advances in Nutrition.
Even in young children, research indicates that more fast food equals more weight gain. Over the course of a year, each additional time preschool-aged children ate fast food in a week, they increased their likelihood of gaining weight, during one April 2020 study in Pediatric Obesity.
According to Danahy, another driver of weight gain is the inflammation fast food can create in the body. "Eating fast food every day, or very often, can increase inflammation in your body, which in turn causes metabolic changes that promote weight gain, especially visceral (belly) fat," she explains. "It also makes it harder to lose weight because visceral fat creates more inflammation."
Fast Food and Chronic Disease
A juicy burger or plate of pizza may taste delicious when hot off the line, but the long-term dangers of fast food on health aren't so appealing. A steady diet of junk food has been associated with a number of chronic diseases, including heart disease. "The unhealthy fats, sugar, refined carbs and salt promote weight gain, high blood pressure, blood sugar and cholesterol, which contributes to cardiovascular disease," Danahy says.
Many low-calorie and low-fat foods are loaded with salt to make them taste better. But taking in a lot of salt can lead to high blood pressure, particularly in those who have overweight or obesity, according to the American Heart Association.
Eating fast food was associated with increased coronary heart disease mortality, and also with an increased risk for type 2 diabetes, according to July 2012 research in Circulation. The study followed more than 52,000 people in Singapore, some of whom consumed "Western-style" fast food items two or more times a week.
Just as well, many of the hallmarks of fast food — such as rapidly digestible refined carbohydrates, red and processed meats, and sugary beverages — contribute to the development of diabetes, according to the Harvard T.H. Chan School of Public Health.
Even mental health may be affected by the frequency of your trips to the drive-thru. Fast food was associated with a higher risk for depression, per a January 2012 study in Public Health Nutrition.
Fast Food and Energy Levels
You may have noticed that eating fast food makes you sleepy and sluggish. That's because one of the other potentially negative effects of fast food is fatigue and low energy levels. Taking in a lot of dietary fat has been associated with both daytime sleepiness and sleep disturbances, according to April 2016 research in Nutrients.
Refined flour, used in fast food burger buns, pancakes, bagels and breakfast biscuits, is made up of simple carbohydrates. These carbs quickly convert into glucose in your digestive system, which is then rapidly released into your bloodstream, per the Harvard T.H. Chan School of Public Health. The resulting glucose spike may cause a brief energy burst; but, any energy spike derived from eating refined flour can leave you sleepy or sluggish, per Harvard Health Publishing.
Like refined flour, refined sugar can cause rapid blood glucose spikes and crashes, contributing to fatigue, according to Harvard Health Publishing. Fast food offerings such as ice cream, cookies, pies, cakes and doughnuts are typically loaded with refined sugar. Sugar is also a common ingredient in hamburger buns, breading, breakfast waffles and pancakes, too.
Harmful Chemicals in Fast Food
Per- or poly-fluorochemicals, also called PFCs, are chemicals that are used to make water-, grease-and stain-repellent coatings for many products, according to the Environmental Working Group (EWG). These chemicals are often found in the wrappings of fast food meal items, and they've been linked to some serious health effects.
Exposure to PFCs has been associated with conditions like high cholesterol, abnormal thyroid hormone levels, kidney and testicular cancer, pregnancy-induced hypertension and preeclampsia, obesity and low birth weight, per the EWG. The organization recommends eating less fast food to limit your exposure to these chemicals.
Is It Bad to Eat Fast Food Every Day?
The evidence paints a convincing picture. For better weight control, reduced risk of chronic disease and overall health, eating fast food every day may not be the best option. Instead, make fast food an occasional treat, and when you're eating it, opt for more nutritious fast food options. Look for items that are lower in calories, fat, sugar and refined carbs, and when possible, choose meals and sides that include fruit and vegetables.
- Anne Danahy, RDN, dietitian, Scottsdale, Arizona
- U.S. Department of Agriculture: “Lettuce, Iceberg (Includes Crisphead Types), Raw”
- American Journal of Preventive Medicine: “Nutritional Quality at Eight U.S. Fast-Food Chains”
- Centers for Disease Control and Prevention: “Caloric Intake From Fast Food Among Adults: United States, 2007-2010”
- Journal of the Academy of Nutrition and Dietetics: “Fast-Food Offerings in the United States in 1986, 1991, and 2016 Show Large Increases in Food Variety, Portion Size, Dietary Energy, and Selected Micronutrients”
- Advances in Nutrition: “Portion Size and Obesity”
- Pediatric Obesity: “Fast Food Intake and Excess Weight Gain Over a 1-Year Period Among Preschool-Age Children”
- Circulation: “Western-Style Fast Food Intake and Cardiometabolic Risk in an Eastern Country”
- Harvard T.H. Chan School of Public Health: “Obesity Prevention Source: Food and Diet”
- Public Health Nutrition: “Fast-Food and Commercial Baked Goods Consumption and the Risk of Depression”
- American Heart Association: Shaking the salt habit
- Nutrients: Associations between Macronutrient Intake and Obstructive Sleep Apnoea as Well as Self-Reported Sleep Symptoms: Results from a Cohort of Community Dwelling Australian Men
- Harvard T.H. Chan School of Public Health
- Harvard Health Publishing: Eating for energy
- EWG: EWG’S GUIDE TO AVOIDING PFCS