The term "fast food" generally refers to food that people intend to consume quickly, either on- or off-site. There is plenty of well-researched evidence demonstrating the various negative health effects of eating and overeating fast food, in both the short- and long-term.

Many fast food establishments now list the number of calories each of their items contains. However, this is only part of the consideration of whether it is healthful or not. Fast food is typically very poor in terms of nutrition. According to a study paper in the journal Health Promotion Perspectives, fast food tends to contain various substances that are generally unhealthful. It is high in sugar, salt, and saturated or trans fats, as well as many processed preservatives and ingredients. It is also low in beneficial nutrients.

Not all fast food is bad, and a person can make an informed choice by doing research to find out the nutritional content of particular fast food items. These are available on the websites of most major restaurants.

However, even the more healthful fast food items are generally high in sugar, salt, saturated fats and trans fats. The Office of Disease Prevention and Health Promotion notes that the typical person in the United States consumes too much of these.

Short-term impact

Because fast food is typically high in sugar, salt, and saturated or trans fats, looking at the short-term effects of these nutrients can help determine what happens in the short-term when a person eats fast food.

The results of a small study in the journal Nutrition Research and Practice suggest that eating foods with more sugar as the first meal of the day could make a person feel hungrier at their next meal than if they ate a low-sugar meal. Doctors, dietitians, and other health experts believe that this is because sugary foods are worse at providing satiety, or a sense of fullness. Also, high-carbohydrate foods increase the body's demand for insulin, which also promotes more hunger within a shorter amount of time after the meal. Experts believe that the more hungry a person is before their next meal, the more likely they are to eat more calories than necessary.

A small study in the Journal of Hypertension found that consuming high levels of salt could have an immediate impact on the proper functioning of a person's blood vessels. Excess sodium intake also has links to fluid retention.

Fast food is also often very low in fresh fruit and vegetables, which makes it hard for people to reach their recommended daily intake of at least 5 servings. It may also be hard for them to reach their ideal fiber intake, which is at least 25 grams per day.

Fast food is highly palatable, meaning that it is very quickly broken down in the mouth, does not require much chewing, and activates the reward centers in the brain rapidly. This combination trains the palate to prefer these highly processed, highly stimulating foods. This reduces someone's desire for whole, fresh foods.

Research from 2018 and other previous studies have suggested a link between fast food consumption and the incidence of food addiction for these low-nutrient items.

Long-term impact

There is plenty of well-researched evidence showing that regularly eating fast food can harm a person's health. This is because most fast food is high in sugar, salt, saturated fat and trans fats, processed ingredients, and calories, and low in antioxidants, fiber, and many other nutrients.

Many fast food meals are very low in fiber. A low-fiber diet is associated with a higher risk of digestive conditions such as constipation and diverticular disease, as well as reductions in healthy gut bacteria.

A study in the journal Health Promotion Perspectives identifies the sometimes irreparable effects of eating fast food on a person's health. Such risks include obesity, insulin resistance, type 2 diabetes, and various cardiovascular conditions.

A study in the Nutrition Journal focuses on the effects of a Western diet on a person's immune system. This is a diet that consists of high amounts of sugar, salt, and saturated fat from only a few sources. The study paper claims that a Western diet can lead to higher inflammation, lower control of infection, higher cancer rates, and higher risk of allergic and autoinflammatory disease.

A study in the journal Thorax establishes a link between fast food consumption in teenagers and children and an increase in asthma, rhinoconjunctivitis, and eczema.

A study in the journal Appetite also suggests that there is a causal link between a diet high in saturated fat and simple carbohydrates, typical of much fast food, and a lower capacity for memory and learning. This sort of diet may also raise the risk of Alzheimer's disease and Parkinson's disease.

The Food and Drug Administration (FDA) suggests that a diet high in salt often increases a person's blood pressure, which means that a person is more likely to have a heart attack, stroke, kidney disease, or heart disease.

The FDA also notes that a diet high in trans fats raises the amount of low-density lipoprotein, or "bad," cholesterol and the lowers the amount of high-density lipoprotein, or "good," cholesterol. This means that a person is more likely to develop heart disease.

The Obesity Action Coalition points out that typical fast food contains a very high number of calories. If a person eats more calories than they are burning during each day, they will put on weight, which may lead to obesity. According to the Centers for Disease Control and Prevention (CDC), obesity increases a person's risk of developing a range of serious health conditions.

Another consequence of younger people regularly eating fast food is their uninentional lack of understanding of basic meal preparation, cooking, and healthful eating. Over time, this perpetuates a dependence on fast food, and people may not learn how to prepare healthful, balanced food in the home. Consuming such meals can support a person's long-term health throughout their lifespan.

Summary

Fast food tends to be high in salt, sugar, saturated fats, trans fats, calories, and processed preservatives and ingredients. A lot of well-conducted research has proven the negative health effects of consuming too much of these.

Not all fast food is bad, however. Some menu items might be lower in these substances than others, while some fast food outlets might focus on providing more healthful options. However, this is not the case for the majority of fast food outlets, or the majority of food items they sell.

To preserve health, a person should try to identify fast food items that contain less salt, fat, sugar, and total carbohydrates and generally try to restrict the amount of fast food they consume.