There are many formulas you can use to calculate a healthy body weight (and we will discuss some of these later), but I love how the text describes a healthy body weight:

• A weight that is appropriate for your age and physical development
• A weight you can achieve and sustain without severely curtailing your food intake and constantly dieting
• A weight that is compatible with normal blood pressure, lipid levels, and glucose tolerance (in other words you are metabolically fit)
• A weight that is based on your genetic background and family history of body shape and weight (after all the apple does not fall too far from the tree)
• A weight that promotes good eating habits and allows you to participate in regular physical activity
• A weight that is acceptable to you

Overall, a healthy size should not be dictated by a formula, or the latest fad or societal expectations.  Healthy sizes come in all shapes and sizes, and you have to determine what a healthy size is for you. 

BMI is a commonly used equation to determine degree of obesity. It is a ratio of a person's body weight to the square of his or her height. You can use the following equation to calculate BMI:

BMI = [weight (lb)/height (in²) ] x 703

BMI puts people into one of five weight categories which is related to a certain health risk:

• Underweight (BMI < 18.5) which is associated with increased risk of health problems.
• Normal weight (BMI from 18.5-24.9) is associated with the lowest health risk.
• Overweight (BMI from 25-29.9) puts people at a higher health risk.
• Obese (BMI from 30-39.9) which increases the risk of diabetes, heart disease and other chronic diseases significantly.
• Morbidly Obese (BMI of 40 or above) putting someone at very high risk for disease.

The Body Mass Index correlates significantly with body fatness, however it is most accurate in determining the degree of obesity, and less useful in determining nonobese people’s body fatness.  Two drawbacks to BMI is that it fails to indicate how much of the weight is fat and where the fat is located.  The location of fat is important because people who store fat more centrally (apple shaped) have a higher risk for chronic disease compared to people who store fat in the hips, thighs, and buttocks (pear shape).

Using just the BMI, at the time of this photo, Michael Jordan would have been considered obese, since BMI does not distinguish between fat and lean body tissue.

C. Measuring Body Composition

DEXA scan.  Although this is the most accurate way to measure body composition, it is very expensive and is usually just done in medical settings.   Underwater weighing.  Traditionally, underwater weighing has been considered the most accurate way to measure body composition. This is based on the principle that fat "floats".   A person is first weighed.  They then exhale as much air as possible and are immersed under water for 10 to 15 seconds for an underwater weight measurement to be taken.  This procedure is repeated 7 to 10 times. Total test procedures may require 45 minutes to one hour.  This technique is not measuring body fat, but body density, which translates mathematically into percent body fat.  During translation, however, significant error can creep into the picture. Error can also happen with using weighing systems that lack precision, and inexperience from the person being weighed. (Clark, 2014)   Fatfold test.  Skinfold calipers are a convenient and inexpensive way to measure body composition.  Keep in mind the accuracy of calipers will depend on the skill of the person taking the measurements, the accuracy of the calipers, and the appropriateness of the conversion equations.   A suitable use is for one person to do the measuring, then the SAME person do it after 3 months or so to see if there's been a change.  Repeated measurements by different technicians, using different calipers, and different conversion equations will yield very different results (Clark, 2014). Bioelectrical impedance.  Bioelectrical impedance analysis measures body composition by sending an imperceptible electrical current through the body. The amount of water in the body affects the opposition to the flow of the current (impedence).  Because water is found only in fat-free tissue, the current flow can be translated into percent body fat. (Clark, 2014) Limitations of this include body fluid levels must be normal which can be impacted by exercise, alcohol, and menstrual cycles.   Above is a hand-held device for measuring body composition using bioelectrical impedence. This is a scale you can stand on and measure body composition using bioelectrical impedence.  Students have told me that there are much cheaper ones available, but I'm not sure of their accuracy. "Bod Pod".  This is a fairly new way of measuring body composition and the one pictured below is at the UO Treatment Center beside Autzen Stadium. While a person sits inside the enclosure, a rapidly vibrating diaphragm in the wall of the test chamber produces small changes in air pressure between it and an adjoining reference chamber. The changes in air pressure can be used to determine the amount of air the person displaces in the test chamber. In turn, that measurement leads to an estimation of the person’s body volume, corrected for the volume of air in the lungs at the time of the measurement. Then, taking the person’s body mass (obtained by a scale) and dividing it by the person’s body volume, the body density is determined. With that, a person’s percent body fat can be calculated.

Keep in mind that body composition can be hard to measure accurately.  Your best bet is to pick one method, and use that method over time to compare numbers and see how they change. But don't get too hung up on the actual number as the accuracy will be questionable depending on the method chosen.

II  What Makes Us Gain and Lose Weight?

A. Energy Balance

Our body weight can fluctuate based on our energy intake (foods we eat) and our energy expenditure (energy we expend during rest and physical activity). This relationship is defined by the energy balance equation.

Energy Balance = energy in - energy out

Positive Energy Balance means energy in > energy out (Weight Gain MAY result)

Negative Energy Balance means energy in < energy out (Weight Loss MAY result)

Equilibrium means energy in = energy Out

The image below illustrates this.

If you consume 3,500 more Calories in a week than your body needs, you COULD gain one pound, because a pound of fat is equal to 3,500 Calories. 

If you expend 3,500 more calories in a week than you take in, you could lose a pound.

Notice I say COULD.  Although the concept of energy balance seems simple it is a dynamic process and is influenced by many factors. In a study of identical twins who were given an extra 1,000 Kcals a day for 100 days some set of twins gained less than 10 pounds, while others gained up to 30 pounds.  People gain and lose weight differently, we don't necessarily follow formulas. Below we discuss the factors that impact energy balance.

There are three parts to energy expenditure (basal metabolic rate, the thermic effect of food, and physical activity)

1. BMR (Basal Metabolic Rate)

If a person is sedentary or moderately active, BMR is the body's largest energy expenditure.  A sedentary person might need about 1800 calories in a day, with about 1200 of them being for the BMR.

An accurate way to measure energy expenditure is to measure oxygen use, since oxygen is needed to complete the Krebs cycle.

Here energy expenditure is being measured for horse racing on an equine simulator.

 

 

2.    Physical activity is the other important way the body expends energy. Physical activity can contribute anywhere from 15-35% of energy expenditure.

Examples of physical activity would be unplanned activities like dashing to class or planned activities like lifting weights or swimming.

3.  Thermic Effect of Food (TEF)

This is the energy needed to digest, absorb, transport, metabolize, and store the nutrients we need.  About 5 to 10% of calories in a food are lost because of TEF.

1. The FTO Gene- There are more than 120 genes that are thought to be associated with an increased risk of obesity. One gene that has got a lot of attention is the FTO (fat mass and obesity-associated) gene. It is estimated that 45% to 65% of people have at least one copy. This gene seems to stimulate excessive food intake and reduce satiety.

2. The Thrifty Gene Theory- This theory suggests that people may have a gene (or genes) that causes them to expend less energy than people with out this this gene (they are energetically thrifty). Although this gene has  not been identified yet, this theory has been applied to populations who have experienced severe feast and famine (Native Americans) who might have benefited from a thrifty gene.  But now consider people with this gene in our current food environment and how it can work against them.

3. Set-Point Theory- This theory suggests that our body fights to maintain our weight within a certain range or "set point". So if we dramatically decrease our calorie intake (fasting or very low calorie diet) our body responds with decreasing our basal metabolic rate which would reduce energy output.

D. Diet Composition- A balanced diet that follows the dietary guidelines for fat, carbohydrate and protein will provide the most satiety.  In other words it is a diet that will fill us up with nutrient dense foods and keep us fuller longer.

1. Foods high in sugar are especially tempting and research shows foods high in rapidly absorbable carbohydrates (sugars and refined starches) may promote eating more in general and create a reinforcing loop for overconsumption of additional rapidly absorbable carbohydrates. (Lucan and DiNicolantonio 2014)   

2. Processed foods are major sources of the nutrients we generally get too much of, including calories and sugar. Processed foods contribute 75% of our added sugar. (Katz, 2014)

E. Metabolic Factors

1. Having a low metabolic rate.

2. Having a low level of spontaneous physical activity.  These are activities like fidgeting or pacing.

3. Having a low fat oxidation which means fat will be stored and more carbohydrate will be burned for energy.

F. Physiological Factors

Hunger is the physical need to eat.  Physical symptoms include our stomach growling and feeling light headed.

Appetite is the psychological desire to eat creating satiety (feeling full).

Some people may not have the ability feel full (an insufficient satiety mechanism) which causes them to over eat.

2.   Energy-Regulating Hormones- Genes direct the making of ghrelin, a peptide hormone produced by the stomach.  Ghrelin stimulates appetite and increases food intake. Levels of this hormone increase before eating, and then fall within 1 hour after eating. Therefore, it is thought that ghrelin plays a role in both hunger and appetite. Ghrelin levels appear to increase after weight loss, which may contribute to the difficulty of maintaining weight loss.

 Genes in fat cells direct the making of leptin, also a peptide hormone, but one that is produced by adipose (fat) cells. It plays a role in body weight regulation by acting on the hypothalamus to suppress appetite and burn fat stored in adipose tissue. Obese people lose their sensitivity to leptin. Perhaps the brain cells of obese people ignore leptin, just as some diabetics' cells (Type 2 diabetics) ignore insulin.

Eve Van Cauter, an endocrinologist at the University of Chicago who is shown above, calls ghrelin and leptin the “yin and yang" of eating regulation.

In experiments by Van Cauter and others, sleep-deprived adults produced more ghrelin, a hormone that promotes hunger, and less leptin, a hormone that signals fullness.

G. External Factors (which include Cultural, Economic, and Social Factors)

I saw the below image at a conference I went to on obesity, where the speaker was  comparing our current situation (a body that is set up to deal with scarcity, not abundance, in an environment where we have every reason to over eat, and not move) to a polar bear in the Sahara dessert.  A polar bear is designed to withstand frigid temperatures, not heat.  We physiologically are wired for hunter and gather lifestyles where we have to work really hard for precious Calories in return.  When we are put into our current "toxic" food environment our bodies go haywire, and as a result are developing chronic diseases like heart disease and diabetes at alarming rates.  

1. Lack of Exercise

 Although some people work out when watching TV, many of us are not moving much, so it takes away from the hours of moving in the day.

And TV can have what I call the "zombie effect".  Two of the children in the photo above have parents who were LCC nutrition faculty at the time and watching TV turned them into "zombies". 
  
Research has shown that while watching TV, BMR falls even lower than just sitting around when you're not watching TV.

People often mindlessly snack when they're watching TV.  Since they're not really paying attention to what they eat, they may eat more than they need to be satisfied.

Many TV ads are for highly processed and high calorie foods and the ads make you want the food.

Many of the actors and actresses on TV have unrealistic body shapes which might encourage eating disorders.       

Here is a link to the above video: https://youtu.be/066XLAptj_U

4.  Weight Cycling is the on again-off again dieting that some people experience.

We get all sorts of cues in our culture that dieting is a good thing.  But weight loss diets seldom are successful in achieving long-term weight loss.  Instead, what can happen after successful weight loss is that the person begins overeating, gaining more weight than what they weighed before the diet. This will be discussed more in lecture 9B.

 

IV  Possible Causes [maybe "contributors" would be a better word] of Eating Disorders (especially anorexia) As we seek to understand another's problems, it's tempting to blame someone (like the person or the parents) and comfort ourselves that the same thing won't happen to us if we just don't do what the other person is doing wrong.  But in addition to not being helpful, that blame can make matters worse instead of better.  It is more likely that a supportive understanding can more quickly lead to the help that is usually necessary for recovery. A friend saw a bumper sticker once that said something like “Children don't choose anorexia and parents don't cause it.”  What other people do can contribute to eating disorders, but other people are not the cause. A person with several of the following contributing factors doesn't mean they have to accept the inevitable and adopt a “victim” mentality.  But if it does happen, quickly getting help can enable them to manage the disorder so it can move to the background of their life. These are my ideas about contributing factors. Genetics.  Eating disorders run in families and it's easy to assume the family environment led to the problem.  Recent studies of twins, presumably raised in the same environment, are finding a clear genetic link. “In a large study comparing the number of identical twins who had anorexia with the significantly smaller number of fraternal twins who had it, scientists concluded that more than 50 percent of the risk for developing the disorder could be attributed to an individual's genetic makeup. A few small studies have even isolated a specific area on the human genome where some of the mutations that may influence anorexia exist, and now a five-year, $10 million NIMH study is underway to further pinpoint the locations of those genes.” (Tyre, Newsweek) Twin studies have also looked at bulimia. “Women with bulimic or anorexic female relatives are four to five times more likely to develop the disorder, and twin studies reveal that the genetic risk factor may be as high as 58 percent.” (Psychology Today) Perhaps genes help create a brain chemistry that can lead people to use starvation (or over-eating) as a way to control anxiety.  Serotonin is a chemical messenger in the brain made from the essential amino acid tryptophan and it affects emotions, behavior, and thought.  Normal levels of serotonin are believed to be associated with feelings of well-being.  Both low and high levels of serotonin may be associated with certain mental health disorders.  Both starvation and over-eating could be attempts to return brain serotonin levels to normal.  It has been suggested that the brain of a person with anorexia may have increased serotonin activity. Control Issues. Most of us have a desire to control what's happening in our lives, and in varying ways.  When we feel ourselves losing that control, some can temporarily “go with the flow” until they can find satisfying ways to re-gain it.  Others may lash out with violent behavior or seek escape with drugs or alcohol.  Still others may decide to use not eating or over-eating to feel a measure of control.  All of these ways of seeking control can have a genetic basis, as evidenced by the incidence of alcoholism in families. Culture.  Our culture places tremendous value on narrow aspects of image such as thinness. Rather than pursuing their unique interests and goals, many who don't fit this image become preoccupied and depressed if they don't naturally fit this image.  When they lose weight, some may tell them how good they look.  This gives the message that they didn't look good before and they can feel they probably don't look good yet.  So they keep dieting and for some reason we don't understand, the eyes of a person with anorexia see a fat person in the mirror, even when they're dangerously underweight. Stressful/Traumatic Events.  Examples I've seen include a teenager whose boyfriend teased her because of her “thunder thighs” and broke up with her, parents who insisted on dieting because their child was being taunted, a parent's serious illness, the stress of college applications, a messy divorce at age 40 and a high-school exchange living situation in Mexico where the family was domineering and demanding. It's impossible to avoid stressful and traumatic events, but empathy regarding the impact of life experiences can be very helpful. V  Do's for Family Members & Friends of People with Eating Disorders (A list is in your lecture notes.)   So what should you do if someone you care about shows signs of an eating disorder?  Treatment seems simple- either eat if the problem is under-eating or don't eat if the problem is over-eating.  But treating a person with an eating disorder as if the treatment is simple can have an opposite-of-the-desired effect and instead make the problem worse instead of better.  One term, a student told me “I developed an eating disorder a couple of years ago at almost 40 years old during my divorce and the people around me chose to try to discipline it out of me.”  She told me that attitude did not help her as she struggled to recover. VI  Top Ten Reasons to Give Up Dieting (A list is in your lecture outline.) The Nondiet Approach (This list, which is in your lecture outline, is from the book below.) Total health  enhancement and well-being, rather than weight loss or achieving a specific "ideal weight." Self-acceptance and respect for the diversity of healthy,  beautiful bodies, rather than the pursuit of an idealized weight at any cost. The pleasure of eating well, based on internal cues of hunger and satiety, rather than on external food plans or diets. The joy of movement, encouraging all physical activities rather than prescribing a specific routine of regimented exercise. Comparison of Traditional Weight Loss Paradigm and Health at Every Size (HAES) Traditional HAES Everyone needs to be thin for good health Thin is not intrinsically healthy and beautiful nor is fat unhealthy and unappealing People are overweight b/c they have no willpower, they eat too much, and move too little People naturally have different body shapes and sizes and different preferences for physical activity Everyone can be thin, happy, and healthy by dieting Dieting usually leads to weight gain, decreased self esteem, and increased risk for eating problems. Health and happiness are not dependent on weight. How does your approach or thoughts about weight loss compare to the above?  Do you take more of a traditional approach or HAES approach?  Which approach do you think would be more positive in a health care setting? Click here for more information bout HAES.   End of Lecture 9A