Does Fast Food Cause Obesity?

Does fast food cause obesity? In short… yes.

While it is certainly not the only cause, fast food restaurants are a big part of the obesity problem.

In fact, how frequently individuals visit fast food restaurants is directly correlated with their weight. According to a 15-year study of 3,000 adults, people who visited fast food restaurants more than twice per week gained roughly 9 to 11 pounds (4 to 5 kg) more than people who visited them less than once per week (1).

The “common sense” reasoning behind the weight gain is that fast food is less healthy than other food, but this assumption is only partially correct.


  1. Unhealthy Ingredients
  2. Larger Portions
  3. Low Cost
  4. Convenience
  5. Patient Community and Expert Advice
  6. Find A Surgeon

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Unhealthy Ingredients

  • Contains more fat and sugar than healthier foods

  • Less vitamins and minerals

Fast Food Unhealthy

There are many types of fast food restaurants – from burgers to pizza to chicken to tacos, but despite their unique menus, the underlying content of their food is the same. Most fast food ingredients contain more energy, total fat, saturated fat, carbohydrates and added sugars than healthier food of the same weight. As a result of these less healthy ingredients, eating fast food has been found to be directly associated with both being overweight and exceeding the recommended levels of fat and sugar (2) (3).

In addition, most fast foods contain substantially fewer vitamins and minerals such as vitamin A, carotene, vitamin C, vitamin E, calcium, magnesium and zinc. Numerous studies have shown that eating healthier foods that contain more of these vitamins and minerals (i.e fruits and vegetables) makes people feel full on less food, leading to more effective weight management (4).

Last and possibly most importantly, most fast food menu items contain a high amount of sugar, often in the form of high fructose corn syrup. Soda is the most popular drink at fast food restaurants and is known to contain high amounts of high fructose corn syrup. Evidence is (re)emerging that suggests sugar could be the true cause of the obesity epidemic and many of the obesity-related health problems.

The following video breaks down what happens to your body when you eat too much fast food:


Larger Portions

  • As average weight has grown, so has portion sizes

Fast Food Portion

As popularized by the 2004 documentary Super Size Me (if you haven’t seen it, you can watch it for free here), the problem with the ingredients of fast food is further compounded by fast foods’ growing portion sizes. It’s no coincidence that portion sizes have grown in parallel with the average person’s body weight from the 1970’s through today (5).

Research has proven that when given larger portion sizes, the average person will still eat their entire meal regardless of whether or not they feel full (6).


Low Cost

  • 2,000 calorie of junk food costs 10x less than same calories of healthy food

fast food low cost

Researchers at the University of Washington found that a 2,000-calorie diet of junk food costs 10 times less than a 2,000 calorie healthy diet (7). This low cost of fast food encourages people to choose it over more expensive healthier food, which is a big reason that lower-income individuals are more likely to be obese (8).

To make things worse, the researchers also found that healthier foods are more likely to increase in cost over time. During their 2-year study, the cost of healthy food went up by 19.5% while the cost of unhealthy food dropped by 1.8%.



  • Fast food restaurants extremely prevalent

Fast Food Convenience

The final factor that makes fast food cause obesity is its convenience, or more specifically, how close fast food restaurants are to your home, job or school.

For instance, children that have a fast food restaurant within 0.10 miles of their school have a 5.2% greater chance of being obese. For pregnant women, the same distance to fast food restaurants increases their obesity odds by 2.5%. No other restaurant types have any correlation with obesity rates (9).


Patient Community and Expert Advice

  • Patient Experiences

  • Ask the Expert

Fast Food Help

If you still have questions about fast food and obesity, our experts are happy to answer them. We (and other patients) would also love to hear about your experiences.

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