We all know fast food isn't exactly health food. While it may be tasty and convenient, eating it on a regular basis has harmful effects on your health, like promoting weight gain and chronic disease. Why? It's partly about what's in your fast food — but also about what's not in your fast food.
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The Downside of Fast
The appeal of fast food is right there in its name: Menu items at these restaurants are intended to be mass produced quickly. However, fast production doesn't usually lead to healthier ingredients or cooking processes. "Traditional fast food (burgers, fried chicken, fries, etc.) tends to be high in sodium, unhealthy fats and sugar because those ingredients make foods taste better to most people," says Anne Danahy, RD, a dietitian based in Scottsdale, Arizona.
Besides adding sodium, sugar and unhealthy fats to your diet, the harm of fast food also lies in nutrients you're not getting when you eat it. Often, fast food restaurants have limited options of 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 health problems caused by fast food have gotten some attention from experts and researchers.
Read more: What Are the Benefits of Fast Foods?
Fast Food and Weight Control
Watching your weight? If so, it may be time to nix the fast food. According to the Centers for Disease Control and Prevention (CDC), eating fast food 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 likely partly to blame for this phenomenon. A study in the Journal of the Academy of Nutrition and Dietetics in June 2019 found that portion sizes and total calories at fast food restaurants have steadily increased since 1986. Another study, in Advances in Nutrition in November 2014, reported that "larger-than-appropriate" portions increased the risk of putting on weight.
Even in young children, research indicates that more fast food equals more weight gain. According to an April 2020 study in the journal Pediatric Obesity, 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.
According to Danahy, another driver of weight gain is the inflammation fast food creates in the body. "Because it's not the highest quality food — with unhealthy fats and sugar — a fast food diet increases 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 the weight. It also creates a cycle 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," says Danahy.
Research published in the journal Circulation in July 2012 found that fast food intake was associated with increased coronary heart disease mortality, but also with increased risk for type 2 diabetes. 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.
And as Harvard T.H. Chan School of Public Health points out, 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.
Even mental health may be affected by the frequency of your trips to the drive-thru. The journal Public Health Nutrition reported in a January 2012 study that eating more fast food was associated with a higher risk for depression.
The evidence paints a convincing picture. For better weight control, reduced risk of chronic disease and overall health, make fast food an occasional treat, not an everyday indulgence.
- 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”