LMCC/Obesity

Body Mass Index

$\left({\frac {\text{weight}}{\text{height}}}\right)^{2}$ (ie. (kg/m)²)

Classification of weight in adults

Classification	BMI
Underweight	<18.5
Normal	18.5-24.9
Class I Obese	30-34.9
Class II Obese	35 - 39.9
Class III Obese	>40

• waist circumference (not waist to hip ratio) can be added to increase the specificity of the BMI. Those at high risk are:
  • Men > 102 cm
  • Women > 88 cm
• There is a U shaped relationship between BMI and mortality, with those over and underweight showing an increase in mortality

Epidemiology

• Prevelence of obesity is > 14% (Canada)
• There has been a doubling of childhood obesity in North America over the last 20 years

Assessment

• Calculate BMI and waist circumference
• Ask about comorbidities
  • Coronary artery disease
  • Hypertension
  • Smoking
  • Lipid profile
  • diabetes
  • Sleep apnea
  • Osteoarthritis
  • Gallstones
• Assess motivation for weight loss and any surrounding support or obstacles
• Examine past attempts and assess for efficacy
• physical exam and investigations are based on specific patient complaints

Management

Weight Loss

If:

• BMI>30
• BMI 25-29.9 or high waist circumference and 2 risk factors
• weight loss is not to exceed 1kg/week with an initial goal of 10% loss in 6 months.

Weight Prevention

• BMI 25-29.9 and less than 2 risk factors

Dietary Therapy

• women: 1000-1200kcal/day
• men: 1200-1600kcal/day
• reduce usual intake by:
  • Obese: 500-1000kcal/day
  • Overweight: 300-500kcal/day
• these reduction will result in a loss of 1kg/week

Temporary and/or drastic diets do not generally lead to long term weight loss. By reducing the caloric intake suddenly, the body will enter a "starvation mode" and losing fat will be more difficult.

What most people who are obese need is a "permanent" change in their eating habits. Progressive substitution of bad products with healthy products will help reduce the shock from a sudden change in their eating style. A reduction of calories about 10% (maximum 20%) of their original caloric intake should do.

Behavioural therapy

• involve patients in goal setting
• self monitor for dietary intake and exercise
• reward when goals are acheived (not with food though)
• dietary behaviour: eat slower, use smaller plates
• modify environmental cues that prompt undesired eating

Pharmacotherapy

• use if lifestyle changes do no work after 6 months
• appropriate if BMI > 30 or >27 with co-morbidities/risk factors
• sibutramine
  • appetite suppresant
  • inhibits norepinephrine and seretonin reuptake
  • side effects: increased BP, tachycardia
• orlistat
  • reduces GI fat absorption
  • side effects: reduction in fat soluable vitamins, stool leakage diarrhea
• ezetimibe
  • cholesterol absorption inhibitor
  • side effects:arthralgias, back pain, diarrhea

Surgery

• for severe obesity
• "stomach stapling", a bariatric procedure

References

Toronto Notes 2005