Obesity Causes

Many factors influence body weight-genes, though the effect is small, and heredity is not destiny; prenatal and early life influences; poor diets; too much television watching; too little physical activity and sleep; and our food and physical activity environment.

What Tips the Scales Toward Excess Weight?

The causes of obesity are as varied as the people it affects.

At its most basic, of course, obesity results when someone regularly takes in more calories than needed. The body stores these excess calories as body fat, and over time the extra pounds add up. Eat fewer calories than the body burns, weight goes down. This equation can be deceptively simple, though, because it doesn’t account for the multitude of factors that affect what we eat, how much we exercise, and how our bodies process all this energy. A complex web surrounds a basic problem.

What are some of the factors that increase the risk of obesity?

Genes Are Not Destiny

Heredity plays a role in obesity but generally to a much lesser degree than many people might believe. Rather than being obesity’s sole cause, genes seem to increase the risk of weight gain and interact with other risk factors in the environment, such as unhealthy diets and inactive lifestyles. And healthy lifestyles can counteract these genetic effects.

Prenatal and Postnatal Influences

Early life is important, too. Pregnant mothers who smoke or who are overweight may have children who are more likely to grow up to be obese adults. Excessive weight gain during infancy also raises the risk of adult obesity, while being breastfed may lower the risk.

Unhealthy Diets

What’s become the typical Western diet-frequent, large meals high in refined grains, red meat, unhealthy fats, and sugary drinks-plays one of the largest roles in obesity. Foods that are lacking in the Western diet-whole grains, vegetables, fruits, and nuts-seem to help with weight control, and also help prevent chronic disease.

Too Much Television, Too Little Activity, and Too Little Sleep

Television watching is a strong obesity risk factor, in part because exposure to food and beverage advertising can influence what people eat. Physical activity can protect against weight gain, but globally, people just aren’t doing enough of it. Lack of sleep-another hallmark of the Western lifestyle-is also emerging as a risk factor for obesity.

Toxic Environment-Food and Physical Activity

As key as individual choices are when it comes to health, no one person behaves in a vacuum. The physical and social environment in which people live plays a huge role in the food and activity choices they make. And, unfortunately, in the U.S. and increasingly around the globe, this environment has become toxic to healthy living: The incessant and unavoidable marketing of unhealthy foods and sugary drinks. The lack of safe areas for exercising. The junk food sold at school, at work, and at the corner store. Add it up, and it’s tough for individuals to make the healthy choices that are so important to a good quality of life and a healthy weight.

Obesity and its causes have, in many ways, become woven into the fabric of our society. To successfully disentangle them will take a multifaceted approach that not only gives individuals the skills to make healthier choices but also sets in place policy and infrastructure that support those choices.

Read more: Obesity prevention

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The aim of the Harvard School of Public Health Obesity Prevention Source Web site is to provide timely information about obesity’s global causes, consequences, prevention, and control, for the public, health and public health practitioners, business and community leaders, and policymakers. The contents of this Web site are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this Web site. The Web site’s obesity prevention policy recommendations are based primarily on a review of U.S. expert guidance, unless otherwise indicated; in other countries, different policy approaches may be needed to achieve improvements in food and physical activity environments, so that healthy choices are easy choices, for all.