Weight Management

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How Does My Weight Affect My Risk?

Causes of Obesity

Excess weight is the result of biological, environmental, and behavioural factors, but, ultimately, it’s a matter of eating too much food and not getting enough physical activity. Sedentary lifestyles combined with overeating leads to weight gain. Examples of trends that influence an individual’s weight include:

  • Inactivity (reduced energy expenditure)
  • Stressful and demanding situations
  • An occupation with few physical demands
  • Inexpensive, fat-laden foods
  • Large portion sizes
  • Easy access to high-calorie foods

Most people’s body weight fluctuates only slightly over the course of a year. But even a small amount of overeating combined with decreased activity can cause weight gain over time. The calories you fail to burn are stored as fat by your body. When substantial overeating is sustained over a long period of time, obesity can result.

Compared with the complexities of weight gain, the logic of weight loss can seem relatively straightforward:

  • To lose weight, you must burn more energy than you take in.
  • One pound of body fat equals 3,500 calories.
  • To lose 1 pound a week, you must expend 3,500 calories by reducing your calorie intake and increasing your activity level.

Genetics is why 25% to 30% of people are overweight. Genes can be responsible for reducing your threshold for weight gain. If you have a family history of obesity, you are more likely to be overweight. The tendency toward obesity based on family history looks like this:

  • People with two obese parents have an 80% chance of becoming obese themselves.
  • Those with one obese parent have a 50% chance of obesity.
  • If neither parent is obese, there is only a 10% chance of obesity.

However, genetic factors contribute to only part of the risk of being overweight or obese, and healthy lifestyle choices can counteract genetic effects.

People tend to put on weight as they age because their metabolisms slow down. The aging process causes the body to become less efficient at regulating the intake of energy. Essentially, the signals that regulate metabolism (calorie usage) change in older people.

Weight gain can be a complicated process. While it’s no mystery that big plates of french fries and buttery pastries can make you fat, the causes of weight gain aren’t always obvious.

You can gain weight when you experience added stress and when you don’t get enough sleep, partly because you might be using food as a coping mechanism. But another reason is your body releases chemicals that allow for more efficient fat storage.

Other reasons people put on weight:

  • Some prescription medications that treat depression, migraines, diabetes, and blood pressure can cause minor weight fluctuations or as much as a 10-pound weight gain per month.
  • Certain medical conditions, most commonly hypothyroidism, can decrease your metabolism and cause weight gain.
  • Menopause can cause women to put on weight in their midsections, when prior to menopause, greater stores of estrogen encouraged fat accumulation in the lower body.

Associated Health Risks

Excess weight, particularly obesity, affects all systems of the body, creating a heightened risk for a range of diseases and conditions, including premature death. It is important to recognize any weight-related health conditions and address them as soon as possible.

Being overweight or obese puts you at risk for any of the following conditions:

  • Coronary heart disease
  • High blood pressure
  • Stroke
  • Pulmonary hypertension and increased risk of congestive heart failure
  • High cholesterol
  • Abnormal lung function
  • Type 2 diabetes
  • Metabolic syndrome (high blood sugar, high cholesterol, and high blood pressure)
  • Cirrhosis of the liver
  • Osteoarthritis
  • Low back pain
  • Gout
  • Cancer — colorectal and prostate in men; breast and ovarian in women
  • Kidney abnormalities
  • Menstrual and ovarian abnormalities
  • Gallbladder disease

Diagnosis and Screening

Body composition analysis is an important tool used to assess the degree to which a person is overweight or obese. It identifies the amount of lean body tissue (fat-free mass — muscle, bone, organs) as compared to the proportion of accumulated fat a person has. Because excess body fat represents a key cause of preventable disease, body composition analysis is part of most medical evaluations.

Two common body composition analysis tools are:

  • Dual energy X-ray absorptiometry (DEXA), which is a body-scan test used to measure bone density, but it also measures body fat percentage and pinpoints exactly where your fat is located.
  • Hydrostatic weighing, which essentially weighs you underwater. Because fat is lighter than water, the more fat you have, the more you’ll float.

In addition to body composition analysis, there are two other screening tools for gauging whether a person is overweight or obese: body mass index (BMI) and waist circumference measure. These are less direct measures of body fat but they are simple and considered accurate indicators.

Body mass index (BMI) is an indirect measure of body composition that takes into account your height and weight. BMI is a globally accepted tool for determining whether a person is overweight or obese. This value is obtained through a simple formula: weight (kg)/height (m)2. To get a sense of how the values are categorized, see the BMI Table below.

Special consideration should be given when applying the BMI to children, who are not yet fully developed; naturally lean individuals; and people with especially muscular builds.

Category Values
Overweight 25.0-29.9
Obese Category I 30.0-34.9
Obese Category II 35.0-39.9
Obese Category III ≥ 40.0

Waist circumference is a measure that is often used in combination with the BMI. It serves as an indicator for the presence of abdominal fat. An overabundance of abdominal fat is referred to as apple-shaped, or “android,” obesity, in men. Women tend toward pear-shaped, or “gynoid,” obesity. Excess fat around the abdomen increases your risk for CVD, type 2 diabetes, breast cancer, and gallbladder disease. In general, the risk of developing health problems rises as waist circumference increases above the cut-off points listed in the chart below.

  Waist Circumference
Caucasian Women < 35 in (88 cm) and Men < 40 in (102 cm)
European Women < 31.5 in (80 cm) and Men < 37 in (94 cm)
Japanese Women < 35.4 in (90 cm) and Men < 33.5 in (85 cm)
South Asian Women < 31.5 in (80 cm) and Men < 34.5 in (90 cm)
South & Central American Women < 31.5 in (80 cm) and Men < 34.5 in (90 cm)

Watch this video to learn how to measure your waist circumference.

Refer to this BMI chart or use this interactive BMI calculator to determine your body mass index.