Energy Balance & Weight Management
Does composition of diet really matter?
"Reduced-Calorie diets result in clinical meaningful weight loss regardless of which macronutrients they emphasize"
recommended rate of weight loss
1-2 lbs per week (1 lb of fat=3500 calories)
a typical person
20-35% physical activity, 5-10% thermic effect of food, 60-65% BMR
BMI&Obesity
30-34.9 Class I 35-39.9 Class II >40 Class III
consequences of obesity
Cardiovascular disease Diabetes Cancer Gallbladder problems Arthritis Social and psychological problems Economic
air displacement plethysmography ("Bod Pod")
Person sits in chamber and computerized sensors determine the amount of air displaced by the person's body. Similar idea to underwater weighing, only uses air.
energy imbalance
Positive Energy Balance: Energy Intake > Energy Output (Weight Gain Growth, pregnancy, lactation, building muscle mass, fat deposition, rebuilding glycogen stores) Negative Energy Balance Energy Intake < Energy Output (Hypocaloric dieting, starvation, undernutrition, fasting, excessive vomiting or diarrhea) Energy Output > Energy Intake Excessive exercise
basal metabolism
energy needed to maintain life when body is at complete digestive and physical rest. TEF = energy required for digestion.
fat cell development
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Portions Served Influence Amount Eaten Bad Popcorn in Big Buckets
Amount of popcorn consumed Greater for larger portions Even when popcorn was stale
Bariatric Surgery. who qualifies
BMI 35 with co-morbidities BMI 40 or great with out co-morbidities FDA recently approved for those with BMI 30-35 (Insurance not yet covering) An estimated 220,000 people with morbid obesity in the U.S. will have bariatric surgery in 2008 About 15 million people in the U.S. have morbid obesity; only 1% of the clinically eligible population is being treated for morbid obesity through bariatric surgery
Bariatric Surgery
Bariatric surgery costs an average of $17,000 - $25,000; Insurance coverage varies by provider Bariatric surgery can improve or resolve more than 30 obesity-related conditions, including type 2 diabetes, heart disease, sleep apnea, hypertension and high cholesterol In general, bariatric surgery patients experience their maximum weight loss 1-2 years after surgery and maintain a substantial weight loss, with improvements in obesity-related conditions, for years. Patients may lose 30% - 50% of their excess weight 6 months after surgery and 77% of their excess weight as early as 12 months after surgery . Long-term studies show up to 10-14 years after surgery, morbidly obese patients who had surgery maintained a greater weight loss and more favorable levels of diabetes, cholesterol and hypertension, as compared to those who did not have surgery
Weight-Loss Strategies: Behavior Modification
Become aware of behaviors Self-monitoring Goal-setting Support groups
Body composition
Body composition = the proportions of muscle, bone, fat and other tissue that makes up a person's total body weight. weight=fat+ lean tissue (water+muscles+organs+bones) Men: Muscle 45% Bone 15% Organs 25% Fat 15% (13-21% is normal) Women: Muscle 35% Bone 16% Organs 24% Fat 25% (23-30% is normal) Can't be measured directly in living humans! A number of ways to estimate.
Dual-Energy X-ray Absorptiometry (DEXA)
Body separated into 3 components: Fat,Fat-free soft tissue,Bone mineral. Also used to determine risk for osteoporosis Very accurate Takes about 20 minutes and involves exposure to a minimal dose of radiation
Energy Out #1: Basal
Body temperature Respiration Heartbeat
Behavior Modification-- internal environment
Cognitive restructuring Alternatives to eating Stress reduction Response to --Hunger --Cravings Rewards Problem solving Relapse training
Multidisciplinary Obesity Treatment
Considered the "gold" standard To change weight -- Dietary energy -- Physical activity Disciplines that contribute to these changes --Nutrition -- Physical activity --Behavior --Pharmacology --Surgery
How is BMR determined
Direct: measure of heat. Sort of similar to bomb calorimeter used to determine calories in food. In insulated chamber surrounded by water. Don't move around. Measure increase in temp. of water. Indirect: gas exchange. C & H in foods combine with oxygen in body, form CO2 and H2O. In lab, hook up mask and measure O2 in and CO2 out, can estimate energy expenditure.
what causes obesity?
Energy intake > energy expenditure ^Intake (Infinite ways to overeat) decreased Expenditure Can't decrease below basal energy expenditure and energy spent on activities of daily living
Obesity
Fat stores can change by whole body energy imbalance brought on by: --Change in energy intake --Change in energy output --Efficiency of energy use
Behavior Modification--external environment
Food environment --Availability of food --Location, location, location --Eating out --Portion sizes Physical environment --To increase NEAT (Non exercise activity thermogenesis) or exercise Support and cooperation --Involving spouses and families (Who shops?Who prepares?) --Coworkers --As part of treatment plan
Estimated Energy Requirement (EER)
For men 19 years and older: EER = 662 - 9.53 x age + PA x [(15.91) x wt) + (539.6 x ht)] For women 19 years and older: EER = 354 - 6.91 x age + PA x [(9.36) x wt) + (726 x ht)] Gender: in general, women have lower BMR than men, and menstrual hormones influence BMR, so 2 sets of equations Age: BMR declines with age since lean body mass diminishes Body size: BMR higher in tall people with larger surface area; also higher the more people weigh
obesity genes
Grehlin (secreted by stomach cells, works in hypothalamus. Hypothalamus - control center of eating.Stimulates appetite and promotes energy storage. Grehlin levels rise when the body is in negative energy balance: it is trying to help maintain a stable body weight) ob gene (leptin) db gene (- leptin receptors)
waist circumference
HIGH RISK: Males >40 inches (102 cm) Females >35 inches (88 cm)Lower "gynoid", upper "android" Upper associated with increased risks of heart disease, stroke, diabetes, hypertension, and some types of cancer. Waist to hip ratio (WHR) provides an index of regional body fat distribution
Dangerous interventions
Herbal products and dietary supplements --Ephedra (Ma Huang or Ephedrine) Banned in 2004 Posed serious health risks to some e.g. Arrhythmias, heart attack, stroke Presented "a significant or unreasonable risk of illness or injury when used according to its labeling or under ordinary conditions of use" (FDA)
food intake
Hunger --Physiological response to nerve signals and chemical messengers (Hypothalamus) --Influences Satiation - stop eating Satiety - not to start eating again
hunger & satiety
Hunger=physiological; appetite=psychological; Satiation: receptors in stomach stretch, nutrients in small intestine causes release of hormones and stimulation of nerves. Messages to the brain (hypothalamus) and person stops eating. Satiety: the feeling that continues to suppress hunger. Determines how long until we want to eat again. Satiation = "stop eating", satiety = "not start eating again". These are physiological though. Can override this! Protein is most satiating; whole grains/fiber produce satiation by filling up the stomach. Fat produces little satiation but does produce satiety. Hypothalamus takes all the various signals - from the mouth, GI tract, & liver - and integrates them. For example, hypothalamus gets message that blood glucose level too low, sends message to stimulate appetite. Chemical messengers - neuropeptide Y is one - potent stimulator of appetite.
Hyperplasia vs. hypertrophy
Hyperplasia - increasing number Hypertrophy - increasing size In children: both happen Adults: mostly hypertrophy increasing size not number
genetics and obesity
If both parents are obese: child has 80% chance of being obese If neither parent is obese, child has less than 10% chance of being obese Biological parents and their children tend to be similar weight, adoptive parents and children do not Identical twins are twice as likely to be the same weight as fraternal twins, even when they grow up apart
Reasons to Increase Physical Activity
Improved health and longevity Improved self-efficacy and mood Associated with weight maintenance Maintenance associated with Expending 4.4 cal/kg/day Walking 54 min/d @ 4 mph Jogging 26 min/d @ 6 mph
Medications
Improves weight loss or # of responders Improve tolerance of hypocaloric diet Appetite suppressants --reduce Hunger --^ Satiety --reduce Food preoccupation --Possibly ^ resting energy expenditure Inhibitors of fat digestion/absorption --^ Fecal loss
Things that affect Basal Metabolic Rate (BMR)
Lean body mass (partly genetic) Body surface area (partly genetic) Gender (genetic) Thyroid hormone (partly genetic) Body temperature Age Nutritional state Pregnancy Caffeine and tobacco use
Bioelectric Impedance
Low-energy electric current Fat resists electric flow Bioelectrical Impedance is another method of assessing body fat percentage. There are a variety of body composition and body fat analyzers and scales available for home use that provide more than just total weight measurements. These devices determine total weight, the percent and amount of body fat, muscle mass, water, and even bone mass. While the readings can be affected by hydration levels, food intake, skin temperature, and other factors, if you follow the directions and take the reading under similar conditions, you will obtain the best results. Your total body water constitutes the largest component (72%) of your fat-free body weight. Bioelectrical impedance analysis (BIA) is based on the fact that the body contains intracellular and extracellular fluids capable of electrical conduction. A non-detectable, safe, low-level current flows through these intracellular and extracellular fluids. Since your fat-free body weight contains much of your body's water and electrolytes, it is a better conductor of the electrical current than the fat, which contains very little water. So this technique is essentially an index of total body water, from which fat-free mass is estimated.
weight loss: aggressive treatments
Medication, surgery
Pharmacotherapy
Orlistat (Ali or Xenical) Phentermine
Current Prevalence: US Adults
Overweight --Approximately 34% Obese --32% -- Over 60 million people
Brown adipose tissue
Oxidation of "regular" fat --> ATP and heat Oxidation of brown fat --> only heat 40% efficient - 40% of energy converted to ATP, rest lost as heat. Brown fat: 100% heat. Energy is spent and not stored. Important in newborns, adults in extremely cold climates, animals in hibernation Amount people have may also be genetic
Causes of Obesity
Patterns Lifelong Overweight children likely to become overweight adults Gradual gains over years/decades Rapid gains associated with life events Gains associated with disease or treatment Lipoprotein lipase (LPL) (Obese people usually have more fat cells, so more LPL activity Promotes storage in fat cells and some in muscle cells)
what's obesity
Positive energy balance leading to Weight gain 75% of gain is fat 25% of gain is fat free mass (Structural protein, Water) ^ Blood volume proportional to ^weight Morbidity and mortality (Due to excess fat)
weight management options
Regulation of Food Intake Meal Replacements or Very Low Calorie Diets (VLCD) Physical Activity Behavior Interventions Pharmacotherapy Surgery
skinfolds
Skinfold thicknesses are the most widely used method of indirectly estimating percent body fat in field and clinical settings. A fold includes the subcutaneous fat layer measured to indicate the body's fat store. Sites often used in combination are the skinfold over the biceps, triceps and in the subscapular and suprailiac areas
Energy Out #2: Thermic effect of food (TEF)
TEF refers to the energy required to process food (digest, absorb, transport, metabolize, and store digested nutrients) TEF is about 5-10% of energy consumed.
Energy Out #3: Physical activity
This is the most variable component of energy output, and the one people have lots of control over! How much you burn during PA will depend on: Your weight—the more you weigh, the more you'll burn (more weight is harder to move) Intensity of exercise Duration of activity
Underwater weighing
Underwater weighing has been considered the gold standard for body composition assessment relies on Archimedes' Principle of displacement which states. The more fat tissue present, the less a person weighs when submerged. Highly accurate but requires special tank and trained technician. Also not everyone is happy about being submerged. Very young, very old, ill may not be able to.From the total body density, the percent body fat can be estimated using the appropriate age-gender equation. One limitation of hydrostatic weighing is that it is based on the two- component model (fat and fat-free mass) which assumes when calculating total body density that the relative amounts and densities of bone, muscle, and water comprising the fat-free mass are essentially the same for all individuals, regardless of age, gender, race or fitness level. Because of this, the lean body mass is overestimated and the body fat is underestimated for many Blacks.
Environmental causes of obesity
convenience foods, on-the-go eating (highly processed, high in calories), an abundance of foods, lack of physical activity (30% regular exercise,30% some/not regular,40% none),poverty
Body Mass Index (BMI)
defined as kg/m2 Correlates well to % body fat After 25 the risk for morbidity and mortality goes up This has become controversial (calculation: 1 kg=2.2 lbs; 1 meter=39.37 in)