What is obesity?

Obesity is a complex disease involving an excessive amount of body fat. It reduces life expectancy as well as the quality of life. 

Obesity increases your risk of other diseases and health problems, such as heart disease, diabetes, high blood pressure and certain cancers.

Obesity is defined as having a body mass index (BMI) of 30 or more. BMI is a calculation that takes a person’s weight and height into account. 

However, BMI does have some limitations. Factors such as age, sex, ethnicity, and muscle mass can influence the relationship between BMI and body fat. 

Also, BMI doesn’t distinguish between excess fat, muscle, or bone mass, nor does it provide any indication of the distribution of fat among individuals.

Despite these limitations, BMI is widely used as an indicator of excess weight.

What causes obesity?

An intake of more calories than your body can burn every day on a prolonged period causes obesity.

With time, these extra calories add up and cause you to gain weight.

Common specific causes of obesity include:

  • Poor diet – Eating foods high in calories
  • Leading a sedentary (inactive) lifestyle
  • Sleep deficit – can lead to hormonal changes that make you feel hungrier and crave certain high-calorie foods
  • Genetics -affects how your body processes food into energy and how fat is stored
  • Age – as you grow older you get less muscle mass and a slower metabolic rate, making it easier to gain weight
  • Pregnancy (weight gained during pregnancy can be hard to lose and may eventually lead to obesity)

Additionally, there are medical conditions may also lead to weight gain. These include:

  • Polycystic Ovary Syndrome (PCOS): a condition that causes an imbalance of female reproductive hormones
  • Prader-Willi syndrome: a rare condition that an individual is born with which causes excessive hunger
  • Cushing syndrome: a condition caused by having an excessive amount of the hormone cortisol in your system
  • Hypothyroidism (underactive thyroid): a condition in which the thyroid gland doesn’t produce enough of certain vital hormones
  • Osteoarthritis (and other conditions that cause pain that may lead to inactivity)

Who is at risk for obesity?

A complex mix of genetic, environmental, and psychological factors can increase a person’s risk of obesity.


Some people possess genetic factors that make it difficult for them to lose weight.

Psychological and other factors

Depression can sometimes lead to weight gain, as people turn to food for emotional comfort. Certain antidepressants can also increase the risk of weight gain.

It’s a good thing to quit smoking, but this can also lead to weight gain. For that reason, it’s important to focus on diet and exercise while you’re quitting.

Medications such as steroids or birth control pills can also put you at higher risk for weight gain.

How do you know you are obese?

Obesity is defined as having a BMI of 30 or more. Body mass index is a rough calculation of a person’s weight to their height.

Other more accurate measures of body fat and body fat distribution include skinfold thickness, waist-to-hip comparisons, and screening tests such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) scans.

Your doctor may also order specific tests to help diagnose obesity as well as obesity-related health risks. These may include blood tests to examine cholesterol and glucose levels, liver function tests, diabetes screen, thyroid tests, and heart tests, such as an electrocardiogram.

A measurement of the fat around your waist is also a good predictor of risk for obesity-related diseases.

What are the complications of obesity?

Obesity is more than simple weight gain. Having a high ratio of body fat to muscle strains your bones as well as your internal organs. It also increases inflammation in the body, which is thought to be a cause of cancer. Obesity is also a major cause of type 2 diabetes.

Obesity has been linked to several health complications, some of which are life-threatening:

  • type 2 diabetes
  • heart disease
  • high blood pressure
  • certain cancers (breast, colon, and endometrial)
  • stroke
  • gallbladder disease
  • fatty liver disease
  • high cholesterol
  • sleep apnea and other breathing problems
  • arthritis
  • infertility

How is obesity treated?

If you’re obese and are unable to lose weight on your own, medical help is available. 

Start with your physician who may be able to refer you to a weight specialist.

Your doctor may also want to work with you as part of a team helping you lose weight. That team might include a dietitian, therapist, and/or other healthcare staff.

Your doctor will work with you on making lifestyle changes. 

Lifestyle and behaviour changes

Your healthcare team can educate you on better food choices and help develop a healthy eating plan that works for you.

 A structured exercise program and increased daily activity — up to 300 minutes a week — will help build up your strength, endurance, and metabolism.

Counselling or support groups may also identify unhealthy triggers and help you cope with any anxiety, depression, or emotional eating issues.

How can you prevent obesity?

Help prevent weight gain by making good lifestyle choices. Aim for moderate exercise (walking, swimming, biking) for 20 to 30 minutes every day.

Eat well by choosing nutritious foods like fruits, vegetables, whole grains, and lean protein. Eat high-fat, high-calorie foods in moderation.