Body Mass Index (BMI) (kg/m 2 ) Surrogate measure of adiposity Weight normalized for height Accurate and inexpensive to measure Weight and height measurements only data needed Limitations: –Insensitive to small changes in weight –May overestimate body fat in those with muscular build and those with edema –May underestimate body fat in older persons and those who have lost muscle mass

Who is overweight? Classification of overweight and obesity by BMI Obesity classBMI (kg/m 2 ) Underweight<18.5 Normal18.5 – 24.9 Overweight25.0 – 29.9 ObesityI30.0 – 34.9 II35.0 – 39.9 Extreme obesityIII>40

BMI and Health Risk ClassHealth Risk NormalNone OverweightIncreased Obesity IHigh Obesity IIVery High Obesity IIIExtremely High Waist circumference – Men >40 in., women >35 in. Type 2 DM, CHD, other atherosclerotic disease, sleep apnea Physical inactivity, ↑ triglycerides 3 or more: smoking, HTN, ↑ LDL, ↓ HDL, IFG, family h/o premature CHD(> 45 YOA men, > 55 YOA women) Additional risks:

Waist-to-Hip Ratio 6 studies (7 as of Nov. 2005) report independent linear relationship between WHR and CHD or CVD WHR may be better predictor of CHD/CVD than BMI Women: 0.8 or less Men: 0.95 or less Challenge to measure?

Health risks of overweight status HTN Dyslipidemia Diabetes CHD CHF Stroke Gallstones Sleep apnea Colon cancer Breast cancer Endometrial cancer Gallbladder cancer Menstrual function and fertility

National Weight Control Registry National registry of reduced-obese subjects who have lost more than 30 pounds and maintained the weight loss for more than 1 year Average age 45, 67% married 80% female, 97% Caucasian Average reported weight loss is 30 kg Average duration of weight maintenance is 5.5 years Provides opportunity to investigate energy metabolism in large heterogeneous group Currently over 5,000 individuals enrolled

Physical characteristics of NWCR subjects (mean ± SD) * Women (n = 2350) Men (n = 607) Total sample (n = 2959) Age (years)44.8 ± ± ± 12.5 Maximum body mass index (BMI) (kg/m 2 ) 36.1 ± ± ± 8.6 Current BMI (kg/m 2 )24.5 ± ± ± 4.6 Change in BMI (kg/m 2 )11.6 ± ± ± 6.2 Maximum weight (kg/m 2 )99.1 ± ± ± 27.1 Current weight (kg)67.2 ± ± ± 15.4 Weight loss (kg)31.9 ± ± ± 18.0 Duration of weight loss (years) 5.7 ± ± ± 7.6 * Two subjects did not report gender. Wyatt et al, Obes Res 10(2):78; 2002

NWCR Method of weight loss MethodWomen (N=355)Men (N=83) No.% % Lost weight on own * Lost weight with assistance Commercial program Self-help group Dietitian * Psychologist Other (physician, nurse, exercise clubs) a Percents add to more than 100% because participants may have used more than one of the types of help. * Statistically significant from women; P<.05.

“The initial goal of weight loss therapy is to reduce body weight by approximately 10% from baseline.” The National Heart, Lung, and Blood Institute Expert Panel on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, 1998.

Moderate weight loss – 10 to 15% of body weight – decreases medical problems in 90% of obese persons, including heart function blood pressure glucose tolerance sleep disorders lipid profiles N Engl J Med, 314: ;1986 Am J Cardiol, 60:55G-58G;1987 Arch Int Med, 147: ;1987 J Am Diet Assoc, 93: ;1993

But how much weight do patients want to lose?

What is reasonable weight loss? 60 obese women years of age Weight kg BMI = kg/m 2 Foster et al, J Consult Clin Psychol, 1997

Defined Weights Dream Weight –Weight you would choose if you could weigh whatever you wanted Happy Weight –This weight is not as ideal as your dream weight; it is a weight however, that you be happy to achieve

Defined Weights, cont. Acceptable Weight –A weight that you would not be particularly happy with, but one that you could accept, since it is less than your current weight Disappointed Weight –A weight that is less than your current weight, but one that you could not view as successful in any way. You would be disappointed if this were your final eight after the program.

Defined Weights % reduction in body weight Dream38% Happy31% Acceptable25% Disappointed17%

Goal weights Goal weight was an average 32% reduction in body weight Three times greater than the NAS and USDA recommended goals Greatly exceeds weight losses of nonsurgical treatments

Dream = 0% % Achieving Defined Weights at Week 48 (n=45) Weight loss: kg

Meta-analysis of 493 studies looking at exercise versus diet Miller et al. Int J Obes Relat Metab Disord 21: , 1997 Pounds lost

Why is diet more effective than exercise in weight loss? Number of minutes necessary to expend calories (160 pound person walking 3 mph): 12 oz. cola36 minutes (150 kcal) Glazed donut58 minutes (242 kcal) Large order of french128 minutes fries (540 kcal)

Exercise is most important for weight maintenance! Only 9% of NWCR participants report maintaining weight loss without regular physical activity Women report an average of 2545 kcal on physical activity per week Men report an average of 3293 kcal per week This level of exercise equivalent to about 1 hour of moderate physical activity (brisk walking) per day Wing and Hill, Annu Rev Nutr 2: ;2001

Six most common activities reported by NWCR participants Activity Walking Cycling Weight lifting Aerobics Running Stair climbing % reporting engaging in activity

Successful Weight Loss Maintenance NWCR participants On average, report consuming 1381 kcal per day (24% kcal from fat) 7.6% report eating less than 90 grams carbohydrate per day Over 44% weigh themselves at least once a day, 31% report weighing themselves at least once a week

Successful Weight Loss Maintenance, cont 72% expend more than 2000 kcal on physical activity per week Self-monitoring food intake was frequently reported Maintaining weight loss for 2 to 5 years decreased the risk of subsequent regain by 50% Wing et al, Annu Rev Nutr, 21:323-41;201

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