Body weight and composition

Learning objectives What are the risks of being overweight or obese? How do we measure body composition? What are the pros and cons of BMI and Waist-Hip ratios? What influences weight? Understand how energy balance influences weight. How can our diet and dieting influence body weight? Describe medical (drug and surgical) approaches to weight loss. What are the costs and benefits? Understand how anorexia and bulimia can adversely affect health.

Body weight What is considered a ‘healthy’ body weight? What is BMI?

Underweight deaths often due to smoking and disease Overweight deaths often due to cardiovascular disease

BMI Underweight: < 18.5 Healthy: 18.5 – 24.9 Overweight: 25 – 29.9 Obese: >30 Why is BMI useful? What are problems with BMI measurements?

BMI risks vary by region

Waist to hip ratio - WHR Visceral fat (around waist) worse than subcutaneous fat (around hips and buttocks) BE AN PEAR, NOT AN APPLE!

WHO waist-to-hip ratio guidelines

Body fat Men: 8-24% Women: 21-35%

Global obesity epidemic

Obesity in the U.S. Obesity varies by ethnic group, age, gender, and region Huge increase since 1990

Health issues related to obesity MANY, including High blood pressure Diabetes High cholesterol coronary heart disease Stroke Sleep apnea Lung problems Difficulty getting pregnant

Factors that influence your weight Energy Balance Genetics Hormones Age and gender Obesogenic environments Availability of ‘fatty’ foods Eating out Large portions Sedentary lifestyle Lack of sleep We can control this the most!

Energy Balance Energy in = energy out Energy in: Energy use: 3500 calories per pound of fat Reducing calories eaten by 3500 calories a week will result in about a pound lost per week (500 cal / day) Energy use: Process food (~10% of energy consumed) Basal metabolic rate (60-70% of energy consumed) Physical activity (10-30% of energy consumed)

Dieting The best type of diet is one that you can maintain for a long time Changes in lifestyle Maintains a healthy, balanced diet Emphasizes Complex carbohydrates Having group support helpful (eg Weight Watchers) Be wary of fad diets Some foods are ‘good’ or ‘bad’ Or ‘fat-burning’ No scientific data support these claims

Very low calorie diets < 800 calories per day Rapid weight loss Muscle loss (including of heart) Metabolism slows even after diet

‘Light’ foods ‘low fat’ foods often replace fat with sugars and salt (sodium) Artificial sweeteners may make you gain weight Body craves more sweet things

Prescription drugs Act on the brain to reduce caloric intake reduced appetite Act on digestive system to reduce absorption of fats Minimally effective if your diet is already low in fat All have side effects

Surgery Major risks and side effects to both

Keeping weight off Control what you can in the energy balance equation Reduce calories you eat Increase calories you burn Exercise!!! Adjust your lifestyle to one that you can maintain for a long time Set realistic goals