What causes obesity?
When you take in more calories than you burn off, you gain weight. How you eat, how active you are, and other things affect how your body uses calories and whether you gain weight.
If your family members are obese, you may have inherited a tendency to gain weight. And your family also helps form your eating and lifestyle habits, which can lead to obesity.
Also, our busy lives make it harder to plan and cook healthy meals. For many of us, it's easier to reach for prepared foods, go out to eat, or go to the drive-through. But these foods are often high in fat and calories. Portions are often too large. Work schedules, long commutes, and other commitments also cut into the time we have for physical activity.
There is no quick fix to being overweight. To lose weight, you must burn more calories than you take in.
Causes and Consequences
Is there a quick answer to the question, "what contributes to overweight and obesity?"
Overall there are a variety of factors that play a role in obesity. This makes it a complex health issue to address. This section will address how behavior, environment, and genetic factors may have an effect in causing people to be overweight and obese.
The Caloric Balance Equation
- Overweight and obesity result from an energy imbalance. This involves eating too many calories and not getting enough physical activity.
- Body weight is the result of genes, metabolism, behavior, environment, culture, and socioeconomic status.
- Behavior and environment play a large role causing people to be overweight and obese. These are the greatest areas for prevention and treatment actions.
Adapted from U.S. Surgeon General's Call to Action to Prevent and Decrease Overweight and Obesity, 2001
When it comes to maintaining a healthy weight for a lifetime, the bottom line is – calories count! Weight management is all about balance – balancing the number of calories you consume with the number of calories your body uses or "burns off."
- A calorie is defined as a unit of energy supplied by food. A calorie is a calorie regardless of its source. Whether you're eating carbohydrates, fats, sugars, or proteins, all of them contain calories.
- Caloric balance is like a scale. To remain in balance and maintain your body weight, the calories consumed (from foods) must be balanced by the calories used (in normal body functions, daily activities, and exercise).
| If you are…
|Maintaining your weight
||"Your caloric balance status is …. in balance." You are eating roughly the same number of calories that your body is using. Your weight will remain stable.
| Gaining weight
||"Your caloric balance status is …. in caloric excess." You are eating more calories than your body is using. You will store these extra calories as fat and you'll gain weight.
| Losing weight
||"Your caloric balance status is …. in caloric deficit." You are eating fewer calories than you are using. Your body is pulling from its fat storage cells for energy, so your weight is decreasing.
Genetics and the environment may increase the risk of personal weight gain. However, the choices a person makes in eating and physical activity also contributes to overweight and obesity.
For more, see Healthy Weight – Balancing Calories.
People may make decisions based on their environment or community. For example, a person may choose not to walk to the store or to work because of a lack of sidewalks. Communities, homes, and workplaces can all influence people's health decisions. Because of this influence, it is important to create environments in these locations that make it easier to engage in physical activity and to eat a healthy diet. The Surgeon General's Call to Action to Prevent and Decrease Overweight and Obesity 2001 identified action steps for several locations that may help prevent and decrease obesity and overweight. The following table provides some examples of these steps.
||Steps to Help Prevent and Decrease Overweight and Obesity
- Reduce time spent watching television and in other sedentary behaviors
- Build physical activity into regular routines
- Ensure that the school breakfast and lunch programs meet nutrition standards
- Provide food options that are low in fat, calories, and added sugars
- Provide all children, from pre kindergarten through grade 12, with quality daily physical education
- Create more opportunities for physical activity at work sites
- Promote healthier choices including at least 5 servings of fruits and vegetables a day, and reasonable portion sizes
Encourage the food industry to provide reasonable food and beverage portion sizes
Encourage food outlets to increase the availability of low-calorie, nutritious food items
Create opportunities for physical activity in communities
How do genes affect obesity?
Science shows that genetics plays a role in obesity. Genes can directly cause obesity in disorders such as Bardet-Biedl syndrome and Prader-Willi syndrome.
Leading a sedentary lifestyle.
However genes do not always predict future health. Genes and behavior may both be needed for a person to be overweight. In some cases multiple genes may increase one's susceptibility for obesity and require outside factors; such as abundant food supply or little physical activity.
With the arrival of televisions, computers, video games, remote controls, washing machines, dish washers and other modern convenience devices, the majority of people are leading a much more sedentary lifestyle compared to their parents and grandparents. Some decades ago shopping consisted of walking down the road to the high street where one could find the grocers, bakers, banks, etc. As large out-of-town supermarkets and shopping malls started to appear, people moved from using their feet to driving their cars to get their provisions. In some countries, such as the USA, dependence on the car has become so strong that many people will drive even if their destination is only half-a-mile away.
The less you move around the fewer calories you burn. However, this is not only a question of calories. Physical activity has an effect on how your hormones work, and hormones have an effect on how your body deals with food. Several studies have shown that physical activity has a beneficial effect on your insulin levels - keeping them stable. Unstable insulin levels are closely associated with weight gain.
Diseases and Drugs
Some illnesses may lead to obesity or weight gain. These may include Cushing's disease, and polycystic ovary syndrome. Drugs such as steroids and some antidepressants may also cause weight gain.
A doctor is the best source to tell you whether illnesses, medications, or psychological factors are contributing to weight gain or making weight loss hard.
Not sleeping enough.
If you do not sleep enough your risk of becoming obese doubles, according to research carried out at Warwick Medical School at the University of Warwick. The risk applies to both adults and children. Professor Francesco Cappuccio and team reviewed evidence in over 28,000 children and 15,000 adults. Their evidence clearly showed that sleep deprivation significantly increased obesity risk in both groups.
Professor Cappuccio said, "The 'epidemic' of obesity is paralleled by a 'silent epidemic' of reduced sleep duration with short sleep duration linked to increased risk of obesity both in adults and in children. These trends are detectable in adults as well as in children as young as 5 years."
Professor Cappuccio explains that sleep deprivation may lead to obesity through increased appetite as a result of hormonal changes. If you do not sleep enough you produce Ghrelin, a hormone that stimulates appetite. Lack of sleep also results in your body producing less Leptin, a hormone that suppresses appetite.