There are several methods used to calculate distribution of
body fat:
1. Waist-hip ratios are valuable in clinical use as they are easily
measured and analyzed. It is the method used to primarily measure
abdominal and visceral fat, as more fat is located in the waist
area and less in the hip area. Waist refers to the circumference
of the body at the level of the umbilicus (belly button) and hip
refers to circumference of the body around the trochanter (at
the level of the hip). The normal waist-hip ratio for men is 1.0,
and for women is 0.8. Individuals with ratios above the normal
are considered upper-body obese.
2. Body Mass Index (BMI) is commonly used to compare subjects
in a research study. It can be calculated using the formula, weight
(kg)/height(m)2. The average male BMI is 25 (considered normal).
A body mass index of 28 for males is considered overweight, while
31 depicts obesity. For females, the numbers are slightly smaller:
21 is normal, 25 is overweight, and 29 is obese.
Both waist-hip ratios and BMI are good predictors of hypertension.
3. Skin fold thickness is another measure of percentage of body
fat and distribution of body fat. Skinfolds of the subscapular
and triceps among others are measured to calculate subcutaneous
fat. An analysis reported in the Health and Nutrition Examination
Survey (HANES) suggests that centrally located fat measured by
the subscapular skinfolds are better predictors of hypertension
than the triceps skinfold. In addition, CT and MR scans measure
subcutaneous and visceral fat. Other determinations of fat have
been accomplished by underwater weighing and fat biopsy.
Genetics (data from studies of twins), overeating, smoking cessation, alcohol consumption, lack of exercise, change in life-style, energy intake vs. energy expenditure (consider resting metabolic expenditure), environmental factors, salt/potassium retention, major depression/anxiety/other psychological, medical illness, medications, during and after pregnancy, cultural (perceptions on obesity), socioeconomic factors.
Fatigue (especially with exercise), shortness of breath, decreased energy, palpitations, irregular heart beat, edema (especially swelling of the feet and legs), sleep apnea (Pickwickian syndrome), respiratory obstruction (for obesity to cause sleep apnea and repitory obstruction it must be severe).
Hypertension (increased blood pressure), coronary heart disease, predisposition to diabetes, hyperlipidemia (increased cholesterol level), metabolic abnormalities, increased risk for gallbladder disease, gout, some types of cancer, development of osteoarthritis of the weight-bearing joints.
Being overweight is a significant risk factor for the development of hypertension. The prevalence of hypertension in the U.S. is greatly increased by the fact that one quarter to one half of all adults (prevalence varies by study) are overweight. Although the association between higher body fat and blood pressure has been recognized for years, recent studies have discovered a 50% to 300% higher incidence of hypertension among adults who consider themselves overweight compared to those classified as normal weight. Similar findings are revealed from studies involving children and young adults, in which the correlation coefficient between weight and blood pressure has been observed to be as high as 0.4. Two proposed mechanisms underlying this correlation are the stimulation of sodium retention and increased catecholamine release, which are results of increased sodium sensitivity and hyperinsulinemia. Age, gender, and race are modifiers/confounders of obesity, and should be considered when studying preventive interventions. Hypertension and obesity treatment are necessary to avoid potential morbidity and mortality from coronary heart disease or stroke.
1. Nonpharmacologic treatment of mild hypertension could
include dietary salt restriction (NaCl), dietary potassium supplementation,
and/or weight reduction, physical exercise, meditation and other
therapies (e.g., biofeedback).
Salt restriction is recommended for those individuals with hypertension
who are "salt-sensitive," or are prone to retaining
sodium, gaining weight, and developing a rise in blood pressure
as a result of a high-salt diet. Those who are "salt-resistant,"
on the other hand, do not experience change in weight or blood
pressure on either high or low-salt diets. For the salt-sensitive
population, extreme amounts of salt restriction are not needed
for improvement of blood pressure. Several studies have shown
that diets containing 1600 to 2300 mg of sodium per day are associated
with average reductions in systolic pressure of -9 to -15 mm Hg
and in diastolic pressure of -7 to -16 mm Hg in salt sensitive
individuals. Thus, salt restriction in this range is recommended
in the dietary management of most individuals with hypertension.
The blood pressure lowering effect of supplemental potassium may
be greater in patients receiving a high-salt diet. The amount
of dietary potassium required to obtain this effect, however,
is not easily obtained.
Six controlled studies of patients with hypertension concluded
that short-term weight loss is usually associated with a reduction
of blood pressure. In patients who experienced a weight loss of
11.7 kg (~25.7 lb.), an average blood pressure reduction of -20.7/-12.7
mm Hg was recorded. A similar study found that a decrease in blood
pressure of -2.5/-1.5 mm Hg per kilogram of reduction of weight,
further demonstrated a significant correlation between weight
change and blood pressure change.
Physical exercise is a critical component of any program to reduce
and control weight on a long term basis. See the following website
for additional information on exercise (link under construction).
2. Pharmacologic treatment of hypertension is essential when the disease has advanced to a more chronic phase. The most common forms of treatment are diuretics, beta blockers, and calcium channel blockers. Controversial and expensive alternatives to dieting in treating obesity are surgery and/or liposuction, which should be used only as a last alternative. Future research for treating obesity includes inhibiting gastric emptying, stimulating lipid oxidation, increasing thermogenesis, and blocking carbohydrate or lipid digestion.
Dietary change, exercise, behavior modification, drug treatment, and/or a combination of these interventions. Limitations on dietary intake, the most common method used for weight loss, can last several weeks to months, depending on individual need and motivation. Altering dietary proportions of fat, protein, carbohydrate, using macronutrient substitutes, and taking vitamins, diet supplements or meal replacements are all techniques to modify food intake. In addition, low calorie diets (1000-1500 calories/day) and very low calorie diets (800 or less calories/day) help patients lose weight. Physician supervision is recommended, however, to prevent adverse side effects, such as excessive loss of lean body mass, particularly in individuals with chronic health problems such as hypertension. Eating and chewing food slowly will send nervous system signals to the stomach that it is "full," and will assist in weight loss and deter weight gain after dieting, especially if a healthy diet is selected. Exercising is another way to lose weight, although the average weight loss from exercise alone is 4-7 lb. (8.8-15.4 kg.), greater weight loss is possible. Regular workouts are advantageous to increasing high-density lipoprotein cholesterol and lean body mass, and diminishing rapid weight gain. Along with changing eating patterns and increasing physical activity, behavior modification produces gradual change.
Four steps to behavior modification include:
1) identifying eating or related life-style behaviors to be modified,
2) setting specific behavioral goals, 3) modifying determinants
of the behavior to be changed, and 4) reinforcing the desired
behavior. Drug treatment is another method used for weight loss.
With prolonged use, however, loss of weight is minimized as it
reaches a plateau. Some side effects are common. An example of
an over the counter drug is phenylpropanolamine which, however,
has a negative effect on blood pressure, and little is known about
it’s long-term side-effects.
On average, 1-1.5 lb./week (~.45-.68 kg./week) are lost by combining
excercise, reducing dietary intake, and behavior modification.
Successful weight loss involves a combination of these methods
that are suitable to the individual in a slow and steady process.
Remember who won the race.
References:
1. Fraser G. Preventive Cardiology. Oxford University Press, New
York, 1986, pp. 134-5.
2. Gerber L, Schnall P, and Pickering T. Body fat and its distribution
in relation to casual and ambulatory blood pressure. Endocrinology
and Metabolism Clinics of North America, Sept. 1995, 24(3).
3. Hurst JW, Logue RB, Rackley CE, et. al. The Heart, Sixth Edition.
McGraw-Hill Book Company, New York, 1986, pp. 1078-9.
4. Methods for voluntary weight loss and control. NIH Technology
Assessment Statement, 1992 March 30-April 1,(10).
5. Moore T and McKnight J. Dietary factors and blood pressure
regulation. Endocrinology and Metabolism Clinics of North America,
Sept. 1995, 24(3).