Obesity: Everything You Need to Know About the Condition

Medically Reviewed by Dr. Samantha Miller, MBChB

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Obesity is a condition characterized by excess body weight. One of the methods most commonly used to assess where one falls is the body mass index (BMI), which measures the ratio between your height and weight. Here, we're exploring the risk factors for becoming obese as well as delving into how obesity is measured and treated. 


What Is Obesity?

While most doctors believe a "healthy" BMI ranges from 18.5 to 25, a person is generally considered overweight if their BMI measures over 25, and, if it's over 30, they are considered obese. Obesity can further be categorized by BMI as class I (BMI of 30 to <35), class II (BMI of 35 to <40) and class III (BMI of over 40).

It is important to understand that BMI is only a rough guideline for measuring obesity. Additionally, many folks, including healthcare professionals, are raising concerns about BMI's validity as a metric. For example, person may have a high BMI for reasons other than obesity, including having an increased muscle mass or bone density. It is important to consider additional lifestyle factors when assessing overall health, such as diet and lifestyle. Nonetheless, BMI is the common metric being used today and, until that shifts, high BMI is often associated with the development conditions such as heart disease, high blood pressure, type 2 diabetes, gallstones, respiratory conditions, and cancer.

Obesity is common, with over 73% of adult Americans being classified as overweight or obese between 2017 and 2018. Considered by some to be one of the most important health issues in the world, obesity's prevalence is continuing to grow. 


Types of Obesity

Simple obesity, or alimentary obesity, makes up about 95% of obesity cases and results from a person continually consuming more calories than the amount of calories they burn in a day.

Secondary obesity results from underlying conditions, such as Cushing's syndrome, polycystic ovary syndrome, hypothyroidism, and insulin-secreting tumors. These kinds of conditions alter the levels of hormones involved in metabolic function, thus impacting how the body stores food or breaks it down into energy.

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Central obesity, or abdominal obesity, is characterized by a disproportionate amount of fat tissue being stored around the stomach. Central obesity is associated with a higher risk of obesity-related health problems, and, for this reason, waist circumference may be measured in addition to BMI.

Childhood obesity occurs when children and adolescents are above the normal body weight for their age and height. Obese children are at risk for long-term problems such as diabetes, hypertension, thyroid problems, and high cholesterol. Even though these health complications are more common among older adults, they can still affect children. Obesity can also cause problems with a child's normal growth and development, and can have significant emotional and psychosocial effects.

Symptoms & Warning Signs Associated With Obesity

Symptoms of obesity include weight gain and an excess of fatty tissue all over the body. Some people may experience pain in the joints and arthritis flare-ups due to the amount of pressure put on the joints by the excess weight. Other associated symptoms include backaches, sleep apnea, heartburn, and indigestion. Obesity can also result in high cholesterol and triglyceride levels; high blood sugar; irregular menstruation; shortness of breath; and other potential complications.


Causes & Risk Factors Associated With Obesity

While excessive caloric intake is the main cause of obesity, there are several other factors which play a role in the development of obesity. While there is no defined gene that causes people to develop obesity, genetics can certainly play a role. For example, children with obese parents are more likely to become obese adults themselves.

Additionally, certain cultural and behavioral factors may play a role. For example, in Western culture, and in the United States in particular, fast food and large portion sizes encourage overeating and the consumption of calorie-dense foods. And, as social eaters, people are likely to center gatherings around food. Furthermore, our lifestyles are becoming increasingly sedentary: Huge numbers of people have desk jobs, which see them engaging in very little physical activity and, therefore, expended much less energy. 

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Obesity may also be caused, or exacerbated by, an underlying medical condition or medication. In fact, some medications, such as steroids, are known to cause weight gain. In addition, injuries or physical ailments may hinder the amount of physical activity an individual is able to engage in, which promotes storage of excess energy as fat.

Non-modifiable risk factors for obesity include age, with those aged 40 to 60 being most likely to be obese; in particular, people experiencing menopause are more likely to develop obesity. Moreover, low socioeconomic status, which is exacerbated by racist systems and racism, which was recently declared a public health threat by the American Medical Association (AMA)Finally, smoking and increased alcohol intake are also shown to increase your risk of developing obesity.

Prevention & Treatment

To prevent obesity, it is important for an individual to know their “healthy weight range” and to be aware of if their weight is creeping up. If one finds that they are gaining weight, small changes can be made to decrease calorie intake or increase calorie expenditure. For those who are already overweight, sustainable weight loss can help them lower their weight and prevent future weight gain.

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For people with primary obesity, the most effective approach for those with class I or class II obesity is dietary changes combined with an increase in exercise. There must be a calorie deficit for weight loss to occur, and this is best achieved with a reduction in overall calorie intake, which may involve substituting calorie-dense foods for filling but calorie-light foods. 

For example, this could mean increasing fruit and vegetable intake while reducing the fat content of your diet. Minor changes rather than drastic diet overhauls generally promote more sustainable weight loss. Exercise is best built up slowly over a period of time to increase tolerance and sustainability and reduce the likelihood of injury.

Medications, such as orlistat (Alli), may be useful to reduce the amount of fat your body can absorb from the diet. There are many “weight loss” pills available as supplements, however many of these are not bolstered by enough evidence that shows significant weight loss, and, in some cases, these supplements may be harmful. As always, speak to your doctor before starting any over-the-counter medication or supplement.

For people with secondary obesity, the underlying condition must be treated. If you are worried you have a medical condition contributing to obesity, speak to your doctor.

Weight-Loss Surgery

Bariatric surgery is a term used to describe any surgical procedure which is performed for the purpose of promoting weight loss. The most common surgical intervention is that of a laparoscopic adjustable gastric band (a Lap-Band or gastric band). Made of silicone, this inflatable ring is placed around the top portion of the stomach via laparoscopic (keyhole) surgery. The band helps to create a space at the top of the stomach and limits how much food patients can eat at any given time. 

The band helps people feel full and eat less at each meal and, over time, the lap band will help the patient lose weight. The laparoscopic band is normally only recommended for patients with a BMI over 40, especially if they are finding it hard to lose weight. Unlike other weight-loss surgeries, the Lap-Band does not permanently alter the digestive tract. The band can simply be deflated and removed in a second procedure to reverse the surgery. If this is done, the stomach will return to its normal capacity.

On the other hand, gastric bypass is a permanent surgical option. The surgeon will attach the small intestine to the top half of the stomach, permanently "bypassing" the lower half of the stomach. This results in a much smaller stomach capacity, so the individual cannot eat as much at once. Gastric bypass may be performed laparoscopically, or you may require an open procedure through the abdominal wall. This procedure is permanent and the individual will always have a smaller stomach capacity.

Finally, intra-gastric balloon surgery involves inserting a balloon down the esophagus (food pipe) into the stomach, where it is inflated. The balloon takes up a large proportion of the stomach, therefore reducing the volume of food that can be consumed at once. Again, this will make the patient feel full more quickly. Oftentimes, the balloon is only left in place for a short period of time before being removed.

Tests & Diagnosis

The diagnosis of obesity is made based on one's visual appearance, weight, and BMI rating. Your doctor may also wish to use skin calipers to measure the thickness of the fat attached to your skin, or they may use a special set of scales to estimate your body’s fat content.

Additionally, your doctor is likely to check for related conditions that, at times, relate to obesity, including diabetes, hypertension, and/or high cholesterol levels. Therefore, you may need to have your blood pressure checked and blood drawn. If any of these conditions are found, you may need to start medication to treat them right away. Many of these conditions can be reversed with healthy and sustainable weight loss.


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