1、,Energy Balance,“State in which energy intake, in the form of food and /or alcohol, matches the energy expended, primarily through basal metabolism and physical activity” Positive energy balance Energy intake energy expended Results in weight gain Negative energy balance Energy intake energy expende
2、d Results in weight loss,Energy Balance,Estimating Kcal Content in Food,Bomb calorimeter Burns food inside a chamber surrounded by water Heat is given off as food is burned The increase in water temperature indicates the amount of energy in the food,Fat Storage,FAT Most fat is stored directly into a
3、dipose tissue Body has unlimited ability to store fat (as fat)CARBOHYDRATES Limited CHO can be stored as glycogen Most CHO is used as a energy source Excessive CHO will be synthesized into fat (for storage),Protein and Fat Storage,Protein is primarily used for tissue synthesis Adults generally consu
4、me more protein than needed for tissue synthesis Excess protein is used as a energy source Some protein will be synthesized into fat (for storage),Macronutrients and Fat Storage,Body prefers to use CHO as energy source Only excess intake of CHO and protein will be turned into fat Fat will remain as
5、fat for storage Physical activity encourages the burning of dietary fatBeta-oxidationMost endurance athletes burn fatty acids for energyglycogen is used also,Energy In Vs. Energy Out,NEATBasal MetabolismDietary Intake Physical ActivityThermic Effect of food,Basal Metabolism,The minimum energy expend
6、ed to keep a resting, awake body alive 60-70% of the total energy needs Includes energy needed for maintaining a heartbeat, respiration, body temperature Amount of energy needed varies between individuals,Influences On Basal Metabolism,Body surface area (weight, height) Gender Body temperature Thyro
7、id hormone Age (2% decline/decade past 30) Kcal intake Pregnancy Use of caffeine and tobacco,Measurement of Bodys Energy Needs,Direct calorimetry Measures heat output from the body using an insulated chamber Expensive and complex Indirect calorimetry Measures the amount of oxygen a person uses A rel
8、ationship exists between the bodys production of energy and oxygen,Physical Activity,Increases energy expenditure beyond BMR Varies widely among individuals More activity, more energy burned Lack of activity is the major cause of obesity,Thermic Effect of Food (TEF),Energy used to digest, absorb, an
9、d metabolize food nutrients “Sales tax” of total energy consumed 5-10% above the total energy consumed TEF is higher for CHO and protein than fat Less energy is used to transfer dietary fat into adipose stores,Harris-Benedict Equation,Estimates resting energy needs Considers height, weight, age, and
10、 gender For men: 66.5 + 13.8x(kg) + 5x(cm) - 6.8x(age in yr.) For women: 655.1 + 9.6x(kg) + 1.8x(cm) - 4.7x(age in yr.),Sample Calculations,Man: 21 yr., 510” (171 cm), 155# (70 kg) 66.5 + 13.8x(70kg) + 5x(171cm) - 6.8x(21) = 1745 kcal/day Woman: 21 yr., 510” (171 cm), 155# (70kg) 655.1 + 9.6x(70kg)
11、+ 1.8x(171cm) - 4.7x(21)= 1536 kcal/day,Why Do You Eat?,Hunger Physiological (internal) drive to eat Controlled by internal body Appetite Psychological (external) drive to eat Often in the absence of hunger e.g., seeing/smelling fresh baked chocolate chip cookies,Satiety Regulator,The hypothalamus W
12、hen feeding cells are stimulated, they signal you to eat When satiety cells are stimulated, they signal you to stop eating Sympathetic nervous system When activity increases, it signals you to stop eating When activity decreases, it signals you to eat,Influences of Satiety,Influences of Satiety,Infl
13、uenced By Body Composition,Leptin A hormone produced by the adipose tissueIncreases with larger fat mass (and decrease desire to eat)Decreases with lower fat mass (and enhance desire to eat)Acts to decrease activity of neuropeptide Y Neuropeoptide YIncreases food intake Reduces energy expenditure,Ho
14、rmonal Influence,Endorphins Natural body tranquilizer that can prompt you to eat CCK Along with gastrointestinal distention, decreases hunger (and desire to eat) Serotonin Neurotransmitter that is released as a result of CHO intake High levels appear to decrease desire to eat CHO and induce calmness
15、,Hormonal Influence,Nutrient receptors In small intestine Elicit feeling of satiety Communicate with the brain via nerves Inform brain of the presence of nutrients in the small intestine Feeling of satiety with the infusing of CHO or fats in the small intestine,Nutrients Influence,Presence of energy
16、 yielding nutrient registers satiety in the brain Apolipoprotein A-IV on the chylomicrons signals satiety in the brain Absence of these nutrients will signal hunger,What is a Healthy Body Weight?,Based on how you feel, weight history, fat distribution, family history of obesity-related disease, curr
17、ent health status, and lifestyle Current height/weight standards only provide guides,Body Mass Index (BMI),The preferred weight-for-height standard Calculation:,Body wt (in kg) OR Body wt (in lbs) x 703.1Ht (in m)2 Ht (in inches)2Health risks increase when BMI is 25,Estimation of Healthy Weight,For
18、men:106 pounds for the first 5 feetadd 6 pounds per each inch over five feetA man who is 510” should weigh 166 lbs.For women:100 pounds for the first 5 feetadd 5 pounds per each inch over five feetA women who is 510” should weigh 150 lbs.,Obesity,Excessive amount of body fat Women with 30-35% body f
19、at Men with 25% body fat Increased risk for health problems Are usually overweight Measurements using calipers,Estimation of Body Fat,Underwater weighing Most accurate Fat is less dense than lean tissue Fat floats,Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or disp
20、lay.,Estimation of Body Fat,Bioelectrical impedance Low-energy current to the body that measures the resistance of electrical flow Fat is resistant to electrical flow; the more the resistance, the more body fat you have X-ray photon absorptiometry An X-ray body scan that allows for the determination
21、 of body fat Infrared light Assess the interaction of fat and protein in the arm muscle,Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.,Body Fat Distribution,Upper-body (android) obesity-”Apple shape” Associated with more heart disease, HTN, Type II Diabete
22、s Abdominal fat is released right into the liver Fat affects livers ability to clear insulin and lipoprotein Encouraged by testosterone and excessive alcohol intake Defined as waist to hip ratio of 1.0 in men and 0.8 in women,Body Fat Distribution,Body Fat Distribution,Lower-body (gynecoid) obesity-
23、”Pear shape” Encouraged by estrogen and progesterone Less health risk than upper-body obesityAfter menopauseupper-body obesity appears,Overweight and Obesity,Underweight = BMI 40,An Epidemic of Obesity,OBESITY,61% of adults in the United States were overweight or obese (BMI 25) in 1999. 13% of child
24、ren aged 6 to 11 years and 14% of adolescents aged 12 to 19 years were overweight in 1999. This prevalence has nearly tripled for adolescents in the past 2 decades. The increases in overweight and obesity cut across all ages, racial and ethnic groups, and both genders. 300,000 deaths each year in th
25、e United States are associated with obesity. Overweight and obesity are associated with heart disease, certain types of cancer, type 2 diabetes, stroke, arthritis, breathing problems, and psychological disorders, such as depression. The economic cost of obesity in the United States was about $117 bi
26、llion in 2000.,Juvenile-Onset Obesity,Develops in infancy or childhood Increase in the number of adipose cells Adipose cells have long life span and need to store fat Makes it difficult to loose the fat (weight loss)Causespoor dietary patternslack of physical activity43% of adolescents watch 2 hours
27、 or more of TV/day,Adult-Onset Obesity,Develops in adulthood Fewer (number of) adipose cells These adipose cells are larger (stores excess amount of fat) If weight gain continues, the number of adipose cells can increase,Causes of Obesity,Nature debate Identical twins raised apart have similar weigh
28、ts Genetics account for 40% of weight differences Genes affect metabolic rate, fuel use, brain chemistry Thrifty metabolism gene allows for more fat storage to protect against famine,Causes of Obesity,Nurture debate Environmental factors influence weight Learned eating habits Activity factor (or lac
29、k of) Poverty and obesity Female obesity is rooted in childhood obesity Male obesity appears after age 30,Nature and Nurture,Obesity is nurture allowing nature to express itself Location of fat is influenced by genetics A child with no obese parents has a 10% chance of becoming obese A child with 1
30、obese parent has a 40% chance A child with 2 obese parents has a 80% chance,Nature Vs. Nurture,Those at risk for obesity will face a lifelong struggle with weight Gene does not control destiny Increased physical activity, moderate intake can promote healthy weight,Why Diets Dont Work,Obesity is a ch
31、ronic disease Treatment requires long-term lifestyle changes Dieters are misdirected More concerned about weight loss than healthy lifestyle Unrealistic weight expectations,Why Diets Dont Work,Body defends itself against weight loss Thyroid hormone concentrations (BMR) drop during weight loss and ma
32、ke it more difficult to lose weight Activity of lipoprotein lipase increases making it more efficient at taking up fat for storage,Why Diets Dont Work,Weight cycling (yo-yo dieting) Typically weight loss is not maintained Weight lost consists of fat and lean tissue Weight gained after weight loss is
33、 primarily adipose tissue Weight gained is usually more than weight lost Associated with upper body fat deposition,Why Diets Dont Work,Weight gain in adulthood Weight gain is common from ages 25-44 BMR decreases with age Inactive lifestyle Changes in body composition Fluid is usually the first weigh
34、t lost Loss in lean body tissue means lowering the BMR Very little fat is lost during weight loss,Lifestyle Vs. Weight Loss,Prevention of obesity is easier than curing Balance energy in(take) with energy out(put) Focus on improving food habits Focus on increase physical activities,What It Takes To L
35、ose a Pound,Body fat contains 3500 kcal per pound Fat storage (body fat plus supporting lean tissues) contains 2700 kcal per pound Must have an energy deficit of 2700-3500 kcal to lose a pound per week,Do the Math,To lose one pound, you must create a deficit of 2700-3500 kcal So to lose a pound in 1
36、 week (7 days), try cutting back on your kcal intake and increase physical activity so that you create a deficit of 400-500 kcal per day- 500 kcal x 7 days = - 3500 kcal = 1 pound of weight lossday week in 1 week,Sound Weight Loss Program,Meets nutritional needs, except for kcal Slow & steady weight
37、 loss Adapted to individuals habits and tastes Contains enough kcal to minimize hunger and fatigue Contains common foods Fit into any social situation Chang eating problems/habits Improves overall health See a physician before starting,Cutting Back,Control calorie intake by being aware of kcal and f
38、at content of foods “Fat Free” does not mean “Calories Free” (or “All You Can Eat”) Read food labels Estimate kcal using the exchange system Keep a food diary,Regular Physical Activity,Fat use is enhanced with regular physical activity Increases energy expenditure Duration and regularity are importa
39、nt Make it a part of a daily routine,Behavior Modification,Modify problem (eating) behaviors Chain-breaking Stimulus control Cognitive restructuring Contingency management Self-monitoring,Cognitive Restructuring,Changing your frame of mind regarding eating Replace eating due to stress with “walking”,
