Energy Balance and Weight Control
Components of Body Weight Water Lean body mass Skeletal mass Fat mass Factors that Influence them Gender/LBM/exercise/diet Gender/genetics/exercise/diet Gender/genetics/exercise/diet Gender/genetics/exercise/diet Gender and genetics typically explains about 40 60% of adult body weight. Exercise and diet explain about 40 60% in relatively equal contributions.
Body fat is an indicator of energy balance: Calories IN vs. Calories OUT If energy IN excess energy OUT then body fat INCREASES as the excess calories are converted to fat for storage. A pound of fat = 3,500 calories Beyond daily expenditure If you drank just one extra Coke each day (150 calories) beyond your daily calorie need, how long would it take you to gain 5 pounds of fat? 116 days To lose a pound of fat, you need to EXPEND 3,500 more calories than you take in.
Internal Factors Nutrient levels Glucose (short term) Fat (long term) Hormones Gut hormones (CCK) Insulin Neurotransmitters Serotonin External Factors Tastes good/looks good Boredom Social interaction Emotional needs Eating as a sport It s time to eat Energy In (eating) What factors influence eating behavior? Why do you eat what you eat when you eat it?
Energy Out: On what do we expend energy? Basal metabolic processes (60 70%) Respiration Circulation Nerve transmission Tissue replacement, turnover, repair Epithelial cells, bone, LBM, etc Basal metabolic rate = BMR = quantification of calories expended on these processes
Energy Out: On what do we expend energy? What factors influence the amount of energy expended via BMR? Body weight If BW decreases, BMR decreases Lean Body Mass If LBM decreases, BMR decreases Caloric restriction If calories decrease, BMR decreases Genetics
Energy Out: On what do we expend energy? Physical activity (20 30%) What factors influence the amount of energy expended on physical activity? Body weight Increased body weight burns more calories Intensity, type, and duration Digestion and absorption (6 10%)
Obesity Associated with an increased risk for almost every major chronic disease CVD Diabetes Hypertension Cancer Associated with infertility, pregnancy and surgery complications, arthritis, gout, gallbladder disease, and sleep problems
How is Obesity Defined? The current method for assessing overweight and obesity is a relationship between weight and height called the Body Mass Index or BMI BMI = Weight (kg) Height (m) 2 BMI = Weight (lbs) Height (in) 2 x 702 Underweight = < 18.5 Normal = 18.5 24.9 Overweight = 25.0 29.9 Obesity = > 30.0
Limitations of BMI Does not consider body composition Does not consider location of excess weight Waist vs. hips and thighs Waist circumference recommendations for: Men: < 102 cm (40 inches) Women: < 88 cm (35 inches) Cut-offs for overweight and obesity assume on-size-fits all with respect to age and ethnicity The BMI and weight for height tables serve as a tool for defining obesity. But how much weight should a person lose?
Weight Control from a Biological Point of View Why is it difficult to lose weight and keep it off? Genetic differences Gender differences Food is life Response to food restriction Adaptation to starvation Environmental influences Changes in body weight and composition as a result of weight loss We don t like to exercise
Keys to Successful Weight Loss and Maintenance of Lost Weight Set reasonable goals for weight loss Eat a balanced diet of REAL foods that is reasonably low in fat and high in fruits, vegetables, legumes, and whole grain carbohydrates Limit consumption of empty liquid calories Pay attention to calorie intake Avoid feelings of denial Be honest and pay attention to your eating behavior Make regular, moderate exercise a part of your routine
What do we know about successful losers? The National Weight Control Registry has been collecting data on a large group of men and women who have lost an average of 65 pounds and kept off a minimum of 30 pounds for at least 5 years Calorie restriction and exercise Over 50% engaged in moderate to heavy exercise Fat intake averaged 24% of total calories 50% continued to count calories or fat grams About 50% lost weight without formal assistance
Fad Diets Promise: Rapid weight loss Example No calorie counting BUT most fad diets do count calories by telling you what to eat and when to eat it To evaluate a diet plan, ask: How long has anyone been able to stay on the plan? How long could you stay on it? Is it nutritionally balanced? Does it encourage exercise?
Fad Diets by Stephen Pfleger
FDA-Approved Diet Pills Sibutramine (Meridia) Increases serotonin Can raise blood pressure Has only been approved for use in the truly obese (BMI > 30) Use results in loss of 10-15% of starting body weight Discontinuation results in weight gain
FDA-Approved Diet Pills Xenical (Orlistat) Works by blocking fat absorption Side effects: oily stools, flatulence unabsorbed fat in the large intestine A clinical trial found that volunteers lost 10% of body weight vs. 6% for those on a placebo Alli Over-the-counter, less potent version of xenical
Other Products Many dietary supplements (vs. drugs) claim to aid in weight loss Some act as diuretics (e.g., high doses of vitamin C) or laxatives (e.g., senna, casara) that promote water loss Stimulants (e.g., ephedra/ma Huang, bitter orange, guarana/caffeine) can increase BMR slightly but are linked to many adverse health effects (e.g., strokes) The vast majority are ineffective (e.g., chromium piccolinate, Chitosan) None will produce significant, sustainable weight loss