Week 6 - Healthy Weights

IntroductionBoth overweight and underweight present risks to healthIt isn’t your weight you need to control; it’s the fat in your body in proportion to the lean – your body composition.The problem of underweight is not as prevalent as overweight, but also poses health threatsstyle.visibilitystyle.visibilitystyle.visibility The Problems of Too Little or Too Much Body Fat The Problems of Too Little or Too Much Body Fat What Are The Risks From Underweight?Deficient body fatness threatens survival during a famine or during diseases.Underweight also increases the risk for any person fighting a wasting disease.style.visibilitystyle.visibility What Are The Risks From Overweight?Most obese people suffer illnesses, and obesity is considered a chronic diseaseObesity elevates the risk of these conditions/diseases:Hypertension Flat feetHeart disease Sleep apnea and problemsStroke Some cancersDiabetes High accident rateHernias Arthritisstyle.visibilitystyle.visibilitystyle.visibilitystyle.visibilitystyle.visibilitystyle.visibilitystyle.visibility Central Obesity Visceral fat Located deep within the central abdominal area of the bodyRaises the risks ofHypertensionHeart diseaseStrokediabetesstyle.visibilitystyle.visibilitystyle.visibilitystyle.visibilitystyle.visibilitystyle.visibility Central Obesity Central ObesityFactors affecting body fat distribution:GenderMenopauseSmokingAlcohol intakePhysical activity How Fat Is Too Fat For Health?Obesity experts evaluate risks to health from obesity using three indicators:BMI, body mass indexWaist circumferenceDisease risk profile and family medical history How Fat Is Too Fat For Health? How Fat Is Too Fat For Health? How Fat Is Too Fat For Health?Fit people are healthier than unfit people of the same body fatnessBeing active – even if overweight – is healthier than being sedentary How Many Calories Do I Need Each Day?Balancing food energy intake with physical activity can add to life’s enjoyment How Many Calories Do I Need Each Day?Two major components of the “energy out” side of the body’s energy budget are basal metabolism and voluntary activities.A third component of energy expenditure is the thermic effect of food. How Many Calories Do I Need Each Day? How Many Calories Do I Need Each Day? Estimated Energy Requirements (EER)The DRI Committee sets Estimated Energy Requirements for a reference man and woman.People’s energy needs vary greatlyReference man: “active” physical activity level, 22.5 BMI, 5 ft 10 in tall, 154 lbsReference woman: “active” physical activity level, 21.5 BMI, 5 ft 4 in tall, 126 lbsstyle.visibilitystyle.visibilitystyle.visibilitystyle.visibility The DRI Method of Estimating Energy RequirementsThe DRI committee provides a way of estimating EER values for individuals. The equation includes:GenderAge – BMR declines by an average of 5 percent per decadePhysical activityBody size and weightGrowth Measures of Body Composition and Fat DistributionBMI is not an accurate measure ofhealthy weights in athletes. Measures of Body Composition and Fat DistributionTechniques for estimating body fatness include these:AnthropometrySkinfold test Waist circumferenceDensityUnderwater weighingAir displacement methodsstyle.visibilitystyle.visibilitystyle.visibilitystyle.visibilitystyle.visibilitystyle.visibility Measures of Body Composition and Fat DistributionConductivityBioelectrical impedanceRadiographic techniquesDual energy X-ray absorptiometry (DEXA) How Much Body Fat Is Ideal?After you have a body fatness estimate, the question arises: What is the “ideal” body fat for a body to have?Ideal for what? Society’s approval or health?For health: Men between 12 and 20 percent body weight as fatWomen between 20 and 30 percent body weight as fatVaries according to gender, lifestyle and stage of lifestyle.visibilitystyle.visibilitystyle.visibilitystyle.visibilitystyle.visibility The Mystery of ObesityWhy do some people get fat?Why do some stay thin?Is weight controlled by heredity?Is it eating habits?style.visibilitystyle.visibilitystyle.visibilitystyle.visibility Why Did I Eat That?Eating behavior seems to be regulated by signals that fall into two broad categories:“go” mechanisms that stimulate eating and “stop” mechanisms that suppress eating Why Did I Eat That? “Go” Signals – Hunger and AppetiteWhat is the difference between hunger and appetite?Hunger – the physical need for foodAppetite – the psychological desire for foodCan you experience appetite without hunger?style.visibilitystyle.visibilitystyle.visibility “Go” Signals – Hunger and AppetiteHunger is stimulated by an absence of food in the digestive tract.Ghrelin is a hormone produced by the stomach and signals the hypothalamus of the brain to stimulate eating. “Stop” signals – Satiation And SatietySatiation occurs when the digestive organs signal the brain that enough food has been consumed. Satiety is the feeling of fullness that lasts until the next meal.Hunger outweighs satiety in the appetite control system.style.visibilitystyle.visibilitystyle.visibility Leptin: A Satiety HormoneThe adipose tissue hormone leptin suppresses the appetite in response to a gain in body fat.The mouse on the right is genetically obese – it lacks the gene for producing leptin. The mouse on the left is also genetically obese but remains lean because it receives leptin injections. Energy Nutrients and SatietySome foods may confer greater satiety than others, but these effects are not yet well established scientifically. Inside-the-Body Causes of ObesityMetabolic theories attempt to explain obesity on the basis of molecular functioning.Quacks often exploit these theories for profit. Selected Metabolic Theories of Obesity Genetics and ObesityA person’s genetic inheritance greatly influences, but does not ensure, the development of obesity.For someone with at least one obese parent, the chance of becoming obese is estimated to fall between 30 and 70 percent.style.visibility Outside-the-Body Causes of ObesityStudies of human behavior identify stimuli that lead to overeating.People can override signals of satiety and hunger and eat whenever they wish. External Cues to OvereatingVariety and availability are strong influences to eat when not hungryStress can cause overeating, especially of comfort foodsExternal stimuli promote eating, such as the time of dayLarge portions encourage overeatingstyle.visibilitystyle.visibilitystyle.visibilitystyle.visibility Physical Inactivity End of Story?The three lifestyle components leading to healthy body weight are diet, physical activity, and behavior change. Moderate Weight Loss Versus Rapid Weight LossEating periodically, storing fuel, and then using up that fuel between meals is a great advantage.If a person eats a balanced diet that meets protein and carbohydrate needs, and moderately restricts calories, the body will use stored fat for energy. Gradual weight loss will occur.style.visibilitystyle.visibility The Body’s Response to FastingIf a person goes without food for 3 days, the body makes several adjustments:Less than a day into the fast, the liver’s glycogen is used up.Where can the body obtain glucose to keep its nervous system going? Not from fat, because fat cannot be converted to glucose.Not from muscle glycogen, because they keep it for their own use.style.visibilitystyle.visibilitystyle.visibilitystyle.visibility The Body’s Response to FastingThe body sacrifices the protein in its lean tissue to supply raw materials from which to make glucose. If the body were to continue consuming its lean tissue unchecked, death would occur in about 10 days. (Death occurs when either fat stores are depleted or half the body’s lean tissue is gone.)To prevent death, the body converts fat to ketones to help feed the nervous system and help spare tissue protein.style.visibilitystyle.visibilitystyle.visibility The Body’s Response to FastingAfter about 10 days of fasting, the brain and nervous system can meet most of their energy needs using ketone bodies. Thanks to ketosis, a healthy person starving with average body fat content can live totally without food for as long as six to eight weeks. The Body’s Response to FastingFasting is not the best way to lose weight.Ketosis upsets the acid-base balance of the bloodFasting promotes excessive mineral losses in urineIntestinal lining loses its integrityLean tissue is lostMetabolism slows downPromotes slower weight loss and slower fat loss than a diet that moderately restricts caloriesstyle.visibility The Body’s Response to a Low-Carbohydrate DietAny diet too low in carbohydrate brings about a response that is similar to fasting.To prevent ketosis and spare body protein, the DRI committee sets a minimum intake of carbohydrate at 130 grams per day, but recommends much more for health. The Body’s Response to a Low-Carbohydrate DietPeople who have healthy body weight consume more, not less, carbohydrate-rich foods The Body’s Response to Fasting What Diet Strategies Are Best for Weight Loss? What Strategies Are Best for Weight Gain?Weight gain requires a diet of calorie-dense foods, eaten frequently throughout the day.Physical activity builds lean tissue, and no special supplements can speed the process. Controversy: The Perils of Eating DisordersAbout 5 million people in the U.S., mostly females, suffer from the eating disorders anorexia nervosa and bulimia nervosa.Many more suffer from binge eating disorder or related conditions.85% of eating disorders start during adolescence.style.visibilitystyle.visibilitystyle.visibility Controversy: The Perils of Eating DisordersAnorexia nervosa Controversy: The Perils of Eating Disorders Anorexia Nervosa Physical PerilsAnorexia nervosa brings the same damage as classic protein-energy malnutrition Treatment of Anorexia NervosaTreatment requires a multidisciplinary approach that addresses food and weight and also involves relationships with oneself and others. 1,000 women die each year, mostly from heart abnormalities brought on by malnutrition or from suicide. Bulimia Nervosa Bulimia Nervosa Bulimia NervosaA typical binge consists of easy-to-eat, low-fiber, smooth-textured, high-calorie foods Physical and Psychological PerilsPhysical and Psychological Perils:Abnormal heart rhythmsSwollen neck glandsUrinary tract infectionsIrritation and infection of the throatTears of the stomach and/or esophagusDental cariesShame, guilt Treatment of Bulimia Nervosa Binge Eating Disorder Eating Disorders in SocietyEating disorders may have many causesSocioculturalPsychologicalHeredityNeurochemical