Definitions | Medical Risks | Causes | Treatment

Contrary to popular belief, being overweight or obese does not mean you have a psychological disorder. However, if your weight is greater than what is considered healthy for your height, there are medical and psychological risks that accompany that excess weight.

By reading Definitions and Causes below, you can learn whether you are overweight or obese, and gain a better understanding of the forces that have made you so.  You can also explore your options for learning to manage your weight by reading the Treatment section at the bottom of the page.

Definitions of Overweight and Obesity

Weight status is defined as a ratio of weight to height called Body Mass Index, or BMI for short. You can calculate your BMI by using the formula below or clicking on Helpful Links, and then searching the Tools Links for the BMI calculator.

BMI = (weight in pounds X 703) / (height in inches)2

Use the table below to determine into which weight category your BMI falls. As your weight moves from Healthy to Overweight and Obese, you increase your risk for developing illnesses associated with excess weight. Equally unhealthy is being Underweight which is typically an indication that you are not getting enough nutrients and energy to keep your mind and body healthy.

Weight CategoryBMI
Underweight< 18.5
Healthy18.5 to 24.9
Overweight25 to 29.9
Class I Obesity30 to 34.9
Class II Obesity35 to 39.9
Class III Obesity≥ 40

Medical risks associated with increasing degrees of overweight and obesity are well-documented and include:
  • Heart disease (which increases the risk of heart attack and death)
  • Dyslipidemia (disorder of fat metabolism – most often unhealthy amounts of fat in the bloodstream; increases risk for heart disease)
  • Stroke (which can kill or permanently disable)
  • Gallbladder disease
  • Various Cancers (particularly endometrial, breast, prostate, and colon)
  • Type 2 diabetes (which increases the risk of heart disease, stroke, blindness, loss of limbs, depression)
  • Hypertension (which increases the risk of heart attack and stroke)
  • Osteoarthritis
  • Sleep apnea (cessation of breathing during sleep)
  • Respiratory (breathing) problems
  • Obstetrical complications
  • Menstrual irregularities
  • Hirsutism (excessive body hair, particularly on the face, torso, and limbs)
  • Stress incontinence (inability to maintain bladder control)

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Medical risks associated with increasing degrees of underweight and malnourishment are also well-documented and described in the section of this website that talks about Eating Disorders.

Causes of Overweight and Obesity

As you can see on the Weight Category table above, the weight range that is classified as healthy for your height is pretty broad. For example, someone who is 5 feet 4 inches tall could weigh anywhere from 108 to 145 pounds before he or she would slip into the higher risk category of Overweight. That is a 37-pound range!  This is important to notice because one of the common contributing causes of overweight is setting either too low a target weight or too narrow a target weight range.

At the core, there are three forces that come together to determine a person’s body size:  biology, psychology, and environment. What makes keeping one’s weight in a healthy range so difficult now-a-days is that the three intertwine — and don’t always cooperate with one another. Biology shapes psychology.  Psychology interprets environment which drives biology. And psychology modifies both biology and environment. Having a reciprocally modifying system like this means that no one-dimensional approach (e.g., a diet or a pill) can effectively control one’s weight over the long run.  Keeping one’s weight in a healthy range requires a multi-faceted strategy.

Obesity has been the subject of theorizing and research for over a century and there is a rich literature that explores the many facets of this complex phenomenon. Despite the nuances and controversies, we can distill the discussion to a simple concept that helps us to address the problem — specifically, that obesity is the result of a mismatch between our biology and our environment.

Biologically, we are built to thrive in an environment in which food is neither easy to come by, nor calorically dense. We evolved to be able to expend great numbers of calories in search of an unpredictable food supply, and survive well enough to become the dominant animal on the planet. When food is plentiful, we store energy for times of scarcity and, while seeking food, we are able to ignore hunger signals to remain focused on the task.  We are also wired not to be very bothered by increasing satiety if good-tasting food is present. (Think about it, if food is hard to come by, it makes good sense to eat as much as you can when it is available!) As recently as a few hundred years ago this design worked well for us.  We worked hard for our food, ate heartily, and few people became obese.  And one more thing, we are born with a particular body type and size potential.  That, along with everything else biological, is a gift from our ancestors.

Today, it is the rare North American who expends much in the way of physical energy to get food. For most of us, hunting and gathering has devolved into driving and ordering. In addition, much of the food we eat has been manufactured in such a way that bite for bite it contains more calories than its natural counterpart did 100 years ago. Thus, our excellent ability to store energy and eat as long as food is available now means that we take in a great number of calories and efficiently store them for a food-deficient future that rarely arrives. Spending few calories to earn our way and having almost eliminated the intermittent famines that thinned our energy stores, we become heavier and heavier. That is at the root of our mismatch problem.

Entwined with our bio-environmental mismatch is that powerful force that sets us apart from the rest of the animal kingdom — our psychology.  Influenced by biology and environment, and influencing both of them, our mental apparatus attaches meaning and expectations to food and eating. They are not only essential to our physical survival, but are also part of our social discourse and enmeshed with our emotional experience.

With so many factors influencing what, when, where, why, and how much we eat, it is easy to understand why weight can be so difficult to manage. When we try to juggle the multiple forces that shape our food intake and try to squeeze our bodies into a smaller target weight (range) than our forefathers bequeathed us, it becomes a recipe for deprivation, frustration, and ultimately weight rebound.  Hence, careful assessment of a reasonable and healthy target weight range is the essential first step in weight management.  That is the key to working with your biology — a task much easier than fighting your biology.

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Treatment of Overweight and Obesity

There are countless weight-loss programs, products, and promises for sale.  In fact, Americans spend billions of dollars in search of slimmer physiques each year.  Yet, two out of three Americans remain overweight or obese and the same weight-loss hopefuls open their wallets again and again for each new promise that pops up in the marketplace.  Considering the entwined forces that drive excess weight, it is not surprising that most of the promises come to nothing more than temporary weight loss followed by disappointment.

While many of the programs and products are potentially useful, most omit what can be thought of as the foundation of weight management.  They tell people what to eat, or offer drugs that mess with biology but do not address psychology or environment.  As such, they supply only surface fixes.  A good analogy is construction of a house.  Regardless of the quality of the building materials, failure to pour a strong foundation will result in a house that soon falls.  With respect to weight control, a strong foundation is constructed of three layers:

  1. Target a weight range that makes sense for you.  If you come from a family with many overweight or obese people, and you are currently obese, it is highly unlikely that you will ever look like the skinny “after” models in the commercials.  If you accept this and set targets that are reasonable for you, you exponentially increase the likelihood of achieving your goals. [Click to open and print your Personal Weight Planning Worksheet.]
  2. Start moving right where you are. Never mind thighs and other body parts of steel.  If you have been relatively sedentary until now, stand up and walk around your sofa. Then keep walking.  [Click here to open and print instructions for Increasing Daily Activity Comfortably.] Weight loss through exercise alone is really tough but weight maintenance without it is almost impossible.
  3. Eat mindfully. This means eating at a Designated Eating Place (the kitchen or dining table at home, lunch room at work/school) and Avoid Attention-Absorbing Activities while you eat (no TV or computer, put away the books and puzzles).  While eating, follow the Mouth/Hand Rule which means that whenever there is food in your mouth, your hands are empty.  This will slow you down and force you to make an active decision before putting more food in your mouth.  As mindful eating becomes part of your daily pattern, it will become easier to modify what, how much, and when you eat.

Most people find that just laying this foundation results in some weight loss.  Depending upon how much weight you are trying to lose, these changes alone may be sufficient.  If not, consider the following guidelines in making your decisions about seeking additional help.

Please notice that no matter how high your BMI and no matter what additional treatments might be reasonable to use, lifestyle change (i.e., healthy diet, increased physical activity, and behavior therapy) are always recommended. In fact, lifestyle change is essential. You cannot continue to live as you have been and expect your body to change.  Weight follows behavior.

If your BMI is:Reasonable options for weight management include:
25 to 26.9Diet, physical activity, & behavior therapy
27 to 29.9Diet, physical activity, & behavior therapy AND Pharmacotherapy if you have medical comorbidities
30 to 34.9Diet, physical activity, & behavior therapy AND Pharmacotherapy if you have medical comorbidities
35 to 39.9Diet, physical activity, & behavior therapy AND Pharmacotherapy AND/OR Bariatric surgery
if you have medical comorbidities
40 or moreDiet, physical activity, & behavior therapy AND Pharmacotherapy AND/OR Bariatric surgery

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