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Weight Management/Obesity/Anorexia

Weeks 5 and 6


Reading:UCSD Nutrition:Chapters 11, 25
New Nutrition:Unit 6

1. Premise: Health and well being are correlated with the maintenance of "ideal" body weight throughout the human life span.

The concept of ideality has non-scientific aspects which include:

A.
  • Esthetics and beauty as observed by a comparison of the female form in a Reuben's painting and the cover of CosmopolitanMagazine. Contrast men's physiques appearing in Body Builders Magazine with those in Gentleman's Quarterly.
B.
  • Economics as seen in societies where greater personal wealth is correlated with thinness (developed nations) or obesity (developing nations).

2. Premise: There are reasons to maintain ideal body weight.

A. The scientific and medical consequences for maintaining ideal body weight include:
  • Actuarial statistics from the Metropolitan Life Insurance Tables which measure the probability that a person of a given sex, age and height will live another year as a function of their body weight..
  • Incidence of human diseases including coronary heart disease, stroke, hypertension, some forms of cancer, late onset diabetes, and gall bladder disease increase with excess weight..
  • Enhanced physical performance including cardiovascular function, skeletal-muscular activity, respiratory capacity, strength and endurance are correlated with ideal body weight.

3. Premise: Ideal body weight can be calculated in many ways.

Several methods have been developed to calibrate ideal body weight:

A. Actuarial tables give the range of body weight for an individual of a given sex, age, height and body build which has the lowest probability for morbidity (incidence of disease) or mortality (death).

B. Body Mass Index (BMI) is the calculated ratio of a person's body weight to their height2 :
BMI =Body weight(in kilograms)
[Height]2(in meters)
See nomogram below. The nomogram permits rapid determination of BMI. To use the nomogram, place a ruler of other straight edge between the body weight (without clothes) located on the left-hand line and the height (without shoes) located on the right-hand line. The body mass index is read from the middle of the scale and is in metric units.
The range for ideal BMI is 20 - 25.

C. Measurement of percent body fat using specific gravity techniques. The person is weighed in air and weighed again fully submerged in water. The density of fat is less than water, while muscle is more dense. Elaborate equipment is required. The ideal % body fat is a function of sex: ideal male 7-19%, ideal female 10-15%.

D. Skin fold thickness can be directly measured at various parts of the body with calipers and correlated with tables of body fat. Requires simple equipment is a reasonably easy to use.

E. Isotopic tracers measure volume of body water (i.e., blood, intracellular, extra cellular) The remaining volume of the body where the isotope does not distribute must be fat Accurate but expensive and complicated procedure

4. Premise: There are many factors that regulate and control body weight:

A. Genetic inheritance of genes which regulate through a variety of biochemical mechanisms including enzymes, hormones, basal metabolic rate, appetite, the number of fat cells, etc. Overweight parents tend to have overweight children.

B. The amount of food (total calories) consumed which depends upon economic status, psycho-social behavior, pleasure, anxiety, stress.

C. Total physical activity levels from "channel surfing" to marathon running and everything in between.

5. Premise: Obesity is a recently defined medical phenomenon

A. Obesity is a defined nutritional problem which only became commonly recognized by the medical community since 1900.

B. Accepted parameters of obesity include:
  • body weight 20% greater than ideal
  • BMI greater than 30
  • body fat greater than 20% for males and greater than 30% for females.

C. The precise mechanisms by which obesity leads to disease are not clear, but are related to amounts of circulating fats (lipids) in the blood, altered properties of cell membranes, response to hormones, physical strain on heart, lungs and circulation.

D. Lean body mass (muscle) has an active metabolism biologically different from stored body fat

E. Weight is gained only when caloric intake exceeds caloric output. Weight is only lost when caloric intake is less than caloric output. Never forget the First Law of Thermodynamics.

6. Premise: There are different types of obesity.

A. Early onset characterized by many fat cells (hyperplasia)

B. Late onset with increased size of normal numbers of fat cells (hypertrophic).

C. Fat deposited in hips and thighs (female)

D. Fat deposited in belly and chest (male). Correlates with heart disease

7. Premise: There are three coherent principles for weight loss management that must be considered and observed at all times:

A. Reduction of caloric intake without compromising intake of essential nutrients. Strategies include eating smaller portions, less snacking, low fat-high fiber foods. Very low calorie crash diets must contain supplements of vitamins, minerals and essential amino acids. "Crashing" lowers the basal metabolic rate and makes weight loss more difficult. When a person slips from the diet weight gain is promoted, leading to the common cycle of loss and gain, the yo-yo effect.

B. Increasing physical activity to burn more calories, increase basal metabolic rate and reduce hunger.

C. Modify behavior by changing eating patterns and reducing the stress of peer and parental pressure, self image.

8. Premise: There is research to identify pharmaceutical aids to appetite reduction.

A. At the present time there are a few pharmaceutical products to reduce appetite and control hunger or safely increase basal metabolic rate. They are only available with a doctor's prescription and are dangerous if not used properly.

B. Some of the most exciting research in nutrition today is the isolation, identification and understanding how some natural, hormone-like small proteins, leptins, may reduce appetite and increase metabolism may be used in weight management.

9. Premise: There are a variety of eating disorders.

A. Anorexia is the refusal or avoidance of eating. Life-threatening starvation and malnutrition are the consequences. The symptoms are pathological weight loss, lowered immune response, failure to thrive.

B. Bulimia is characterized by binge eating followed by purging either with laxatives or regurgitation. Weight loss is not as severe as seen in anorexia, but nutritional deficiencies, tooth decay, and altered water balance is observed.

C. Estimates of the frequency of these conditions in adolescent females are as great as 10-12%. Incidence in males is much less frequent.

D. These eating disorders are frequently by real or perceived parental and/or peer pressures, or by poor self image. Professional counseling may be needed to prevent serious illness.
Perhaps Goldilocks and the Three Bears have the correct answer to most nutritional issues. "Not to little. Not too much. But just right."


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