ObesityCauses of Obesity

Let's Talk About the Causes of Obesity

Learn about the varied and complex factors that make a person vulnerable to this condition as we get to the roots of the matter.

    Our Pro PanelObesity Causes

    We went to some of the nation's top experts on obesity to bring you the most up-to-date information possible.

    Sharon Zarabi, RD headshot.

    Sharon Zarabi, R.D.Registered Dietitian and Bariatric Program Director

    Lenox Hill Hospital
    New York, NY
    Robert F. Kushner, M.D. headshot.

    Robert F. Kushner, M.D.Medical Director

    Center for Lifestyle Medicine at Northwestern Medicine; Author of "Six Factors to Fit: Weight Loss That Works for You!"
    Chicago, IL
    Sara N. Bleich, Ph.D.

    Sara N. Bleich, Ph.D.Professor of Public Health Policy

    Harvard Chan School of Public Health
    Boston, MA

    Frequently Asked QuestionsObesity Causes

    What are five causes of obesity?

    The causes of obesity range from those steeped in nutrition, exercise and genetics to living in an obesogenic environment. Five common causes include a surplus of calories (taking in more calories a day than you burn); calorie quality (ultra-processed foods and beverages like chips, candy and soda promote overeating); having a family history of obesity; poor sleep (sleep helps regulate hunger and satiety hormones); and taking certain obesity-promoting medications (antidepressants, anti-anxiety drugs, and mood-stabilizing drugs, for example, activate brain receptors that increase appetite or decrease the number of calories burned).

    What foods cause obesity?

    No single food causes obesity, but certain foods are known to promote obesity when consumed in large quantities, particularly in people who are prone to obesity or who live in obesogenic environments. For instance, ultra-processed foods and beverages have been engineered using fat, sugar, salt, and other addictive ingredients to light up the reward centers of the brain, driving us to continue eating. But because there’s no protein or fiber to fill you up, your brain tells you to keep eating and eating.

    How does fast food cause obesity?

    Fat food restaurants are part of our obesogenic (or obesity-promoting) environment. Not only do the heavily processed foods served at fast food restaurants drive you to continue munching, but their ballooning serving sizes don’t exactly encourage moderation. In the 1950s, a typical fast food beverage was seven ounces. Today it’s 42 ounces. Hamburgers and fry portions are three times bigger than they ones were, as well. When we’re given a bigger portion of food, we tend to eat more of it.

    How can sugar cause obesity?

    While sugar doesn't necessarily cause obesity, especially not when consumed in the form of an occasional treat, it is a risk factor for obesity, and mounting evidence strongly suggests that consuming a diet high in added sugars,found in candy, baked goods, and sweetened sodas and juices, is known to promote weight gain and obesity. While these sweet crystals may taste great, they provide calories without nutrition, a.k.a. "empty calories." (This does not apply to foods that contain naturally occuring sugars, like fruit. Those calories are far from empty, as they also provide vitamins, fiber, antioxidants, and more.)

    Foods high in added sugar — like cookies and ice cream—tend to also be high in calories, and excess calories are tied with obesity. Because these foods taste delicious and aren’t terribly filling, they send a message to the brain that says, "Keep eating." That, in turn, can promote obesity. Additionally, frequent sugar intake raises blood sugar levels, which can lead to a condition called insulin resistance which promotes fat storage.

    Leslie Goldman

    Leslie Goldman


    Leslie Goldman is a health and wellness writer who regularly contributes feature stories and essays to various publications.