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Healthy body weight

Many Canadians weigh too much – more than half of us are overweight or obese. This puts us at increased risk for breast, colorectal, esophageal, gallbladder, liver, kidney, pancreatic and uterine cancer. Maintaining a healthy body weight is a goal that most people can reach.

Body weight and cancer

Research shows that being overweight or obese increases your risk of cancer. Reduce your risk by getting to and staying at a healthy body weight.

What’s a healthy body weight?

A healthy body weight will be different for everyone, so check with your doctor about what a healthy body weight is for you. Being at a healthy body weight does not mean being skinny like a model, but you might be surprised to learn how much “extra” weight makes you obese or even just overweight from a medical point of view.

  • Body mass index

    A tool called body mass index (BMI) can be used to help decide when adults may be at risk for developing health problems because they are underweight or overweight. BMI uses a chart based on weight and height. BMI is calculated by dividing people's weight (measured in kilograms) by their height (measured in metres squared). The result is looked up in the table to determine the risk of developing health problems.

    Health risk and body mass index (BMI) 

    Group BMI (kg/m2) Risk of developing health problems
    underweight less than 18.5 increased risk
    normal weight 18.5–24.9 least risk
    overweight 25–29.9 increased risk


    obese class I

    obese class II

    obese class III 

    30 or more



    40 or more

    high risk

    very high risk

    extremely high risk

    Source: Health Canada

    BMI is not used the same way for people under 18 or women who are pregnant or breastfeeding. Finding out a child’s BMI is different than for adults. Children and adolescents are still growing and their amount of body fat changes as they grow. BMI charts are also different for boys and girls. Talk to your doctor to find out if your child is underweight or overweight for their age.

    Drawbacks of using BMI

    BMI is not a perfect tool. There are some drawbacks to using it as a measure of obesity.

    •  BMI is an indirect measure of body fat.
    • BMI does not necessarily reflect the changes that occur with age.
    • BMI and body fat actually differ for men and women. Women often have a greater percentage of body fat, but this is not reflected in height and weight measurements.
    • BMI may not reflect the difference between excess body fat and muscle mass. For example, lean people, such as athletes, with high muscle mass sometimes have high BMI scores.
    • BMI may be based on self-reported height and weight, which can affect accuracy.
  • Waist circumference

    Waist circumference (WC) is another indicator of health risk associated with excess abdominal fat (fat around the belly). Excess fat around the waist and upper body (an "apple" body shape) is associated with a greater health risk than having more fat in the hip and thigh areas (a "pear" body shape). WC is measured around the abdomen from the bottom of the lower rib and the top of the pelvic bone while a person is standing.

    In general, the risk of developing health problems, including cancer, increases as WC increases above 102 cm (40 inches) in men and 88 cm (35 inches) in women. Even though a person's BMI may be in the normal weight range, a high WC indicates some health risk. Excess abdominal fat increases the risk of colorectal cancer and may increase the risk of pancreatic, post-menopausal breast and uterine (endometrial) cancer. 

  • Tips to maintain a healthy body weight
    • Follow Canada's Food Guide and eat a well-balanced diet that includes a variety of vegetables and fruit and lots of fibre each day, but has little fat, little sugar and less processed food.
    • Try to drink at least 6–8 glasses of water (or other caffeine-free fluid) each day. When you are physically active or when it is hot outside, drink more water.
    • Follow physical activity guidelines for your age group.
    • Talk to your doctor or a registered dietitian if you need to lose weight. Small, gradual changes to what you eat and how active you are can make a difference.
      • Try not to skip meals because this may cause overeating later.
      • Replace high-fat foods, beverages and snacks with low-fat choices. Choose leaner cuts of meat. Avoid high-calorie foods.
      • Eat smaller portions and plan meals around vegetables, fruit and grain products.
      • Be aware of diets and exercise products that promise quick and easy results. Most diets fail because staying at a healthy weight depends on more than just cutting down on the amount of food you eat or exercising for a short period of time.


Morgan Smith Even though we are high school students, we were able to raise so much money for the Canadian Cancer Society. It just goes to show what can happen when a small group of people come together for a great cause.

Read Morgan's story

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