Chapter Eight - Part One Weight Control Food & Nutritional Health NUT SCI –242 Karen Lacey, MS, RD, CD © Spring 2005

Terms Overweight: 10% - 20% above the desirable weight for height, or a BMI of 25.0-29.9 Underweight: 10% or more below the desirable weight for height, or a BMI of less than 18.5 Obesity: 20% or more above the desirable weight for height, or a BMI of 30 or greater

Problems Associated with Underweight Due to decreased body fat stores, may be disadvantaged when energy reserves may be needed, such as during physiological stress, injury or famine Other problems include: Menstrual irregularity Infertility Osteoporosis

Problems Associated with Overweight High blood pressure High cholesterol Diabetes Heart disease Gallbladder disease

I. What is a Healthful Weight? Body Weight vs. Body Fat Body weight and body fat are not the same thing Body composition is important

B. Measuring Body Fat Difficult to measure Methods include: Underwater weighing: the entire body is submerged into a tank of water and water displacement is measured to determine body density and body fat percentage

Cont’d Biochemical Impedence: estimate body fat content by measuring how quickly electrical current is conducted through the body Fat increases resistance against electrical current

Cont’d Skinfold Test: thicknesses of folds of skin various places on the body are measured with an instrument called a caliper Simple & inexpensive

C. Distribution of Fat Central obesity: excess fat on the abdomen and around the trunk Central obesity represents a greater risk to health than fat elsewhere on the body

D. Weighing in for Health Health risk is dependent upon three factors: Body weight Amount & location of body fat Current health status Waist circumference: a measure used to assess a person’s abdominal fat

Cont’d Body Mass Index (BMI): an index of a person’s weight in relation to height which correlates with total body fat content

II. Energy Balance Fat stores= energy in – energy out Energy in: Calorie content of food taken in 3,500 calories = 1 pound of body fat Energy out: Basal metabolism: the energy required to fuel the activities of the cells necessary to sustain life

Cont’d Fuel for voluntary activities Number of calories an activity uses is determined by: Muscle mass required Weight of body part being moved Duration of activity

III. Causes of Obesity Genetic vs. Environment Set-pt. Theory: the theory that the body tends to maintain a certain weight by adjusting hunger, appetite and food energy intake compared to metabolism so that a person’s effort to alter weight may be unsuccessful Fat-cell Theory

Cont’d Heredity may contribute to obesity Factors in surroundings encourage eating Availability, variety, appearance, lighting, music, location, companions External cue theory: the theory that some people eat in response to such external factors as the presence of food or the time of day rather than to such internal factors as hunger

B. Environment & Behavior Hunger A physiological sensation A negative experience people eat to avoid Appetite A physiological experience A positive experience- people eat for enjoyment

Cont’d Satiety The condition of being full or satisfied A signal to stop eating Other regulators: Human sensations Emotions Situations Arousal (ie, stress eating) Underactivity