Understanding Body Mass Index (BMI)

• Body Mass Index (BMI) is also known as the Quetelet Index

Calculating BMI

• BMI is calculated using weight in kilograms divided by height in meters squared
• To convert pounds to kilograms, divide pounds by 2.2
• To convert inches to meters, multiply inches by 0.0254
• Alternatively, BMI can be calculated using weight in pounds divided by height in inches squared, then multiplied by 704.5

BMI Classifications

• Underweight: BMI is less than 18.5
• Normal: BMI is between 18.5 and 24.9
• Overweight: BMI is between 25 and 29.9
• Obesity I: BMI is between 30 and 34.9
• Obesity II: BMI is between 35 and 39.9
• Extreme Obesity (Obesity III): BMI is 40 or greater

BMI Advantages

• Data is easy to gather
• Correlates well with actual body fat measurements (r = 0.70)

BMI Disadvantages

• May not accurately predict risk across all populations
• Excess body fat increases health risk, not weight itself
• Cannot determine fat mass or lean mass

Waist to Hip Ratio (WHR)

• WHR is the circumference of the waist divided by the circumference of the hips
• It indicates regional fat distribution, or body fat pattern
• Upper body fat indicates android obesity
• Lower body fat indicates gynoid obesity
• WHR risk varies with age and gender

Waist Circumference

• Waist circumference is an excellent predictor of risk for chronic disease
• High risk for men: over 102 cm (40 inches)
• High risk for women: over 88 cm (35 inches)

Body Composition

• Body composition is fat weight (fat mass) expressed as a percentage of total body weight

Two-Component Model

• Fat Mass (FM) consists of all extractable lipids, with approximately 10% water
• Fat-Free Mass (FFM) or Lean Body Mass (LBM) consists of water, protein, and mineral components, with around 70-80% water

Measuring Body Composition

• All methods used estimate body composition

Body Composition Measurement Techniques/Methods

• Laboratory methods include hydrostatic weighing, air displacement plethysmography (ADP), dual-energy X-ray absorptiometry (DEXA/DXA), total body electrical conductivity (TOBEC), computed tomography (CT), and magnetic resonance imaging (MRI)
• Field methods include skinfolds (SKF), bioelectrical impedance analysis (BIA), near-infrared reactance (NIR), and ultrasound (US)

Prevalence of Obesity (2025)

• 32.2% of males will be obese

  • Class I: 21.5%
  • Class II: 6.5%
  • Class III: 4.2%

• 35.5% of females will be obese

  • Class I: 17.8%
  • Class II: 10.5%
  • Class III: 7.2%

• 41.9% of adults over 20 are obese

• 31.7% are overweight

• 26.4% have normal body weight or are underweight

• 73.6% are either overweight or obese

Prevalence of Anorexia Nervosa

• Lifetime prevalence is 0.6%
  • Females: 0.9%
  • Males: 0.3%

BMI-Associated Disease Risk

• Underweight poses an increased risk
• Normal weight signifies a normal risk
• Overweight indicates increased risk
• Obesity I signifies high risk
• Obesity II indicates very high risk
• Obesity III indicates extremely high risk

Obesity and CVD

• Obesity leads to an increased incidence of CHD/CVD and cerebrovascular disease (CVA) and PVD/PAD

Blood Lipids and Obesity

• Obese individuals are more likely to have higher total cholesterol, higher LDL, lower HDL, higher Total C:HDL-C Ratio, and higher TG

Cancer and Obesity

• An ACS study of over 1 million men and women revealed that obese men had higher mortality rates for cancers of the colon, rectum and prostate, and obese women had higher mortality rates for cancers of the gallbladder, bile ducts, breast, uterus, and ovaries

Psychological/Emotional Problems

• Obesity can cause psychological burden, societal pressures to be thin, feelings of guilt, depression, anxiety, low self-esteem, discrimination and prejudice, decreased chance of marriage, and poorer academic performance

Obesity & Other Health Concerns

• Respiratory problems, sleep apnea, infertility and complications of pregnancy such as gestational diabetes and neural tube defects are health concerns with obese people

• May also cause menstrual irregularities, gallbladder disease, carpal tunnel syndrome, and hormonal problems, including increased insulin production and decreased testosterone in males

• Obesity increases health risk

• Body fat distribution is also an important predictor of risk for T2DM and CVD

• Fitness ameliorates some of the negative consequences of obesity

• It’s better to be "fit and fat" than "unfit and lean"

• There are several types of obesity and multiple causes

• Obesity is a complex disorder with multiple genetic and non-genetic influences

Energy Balance

• Energy balance is a complex interaction between energy intake and energy expenditure

Energy Expenditure

• The basal metabolic rate (BMR) is the energy utilized at complete rest
• Typically measured in the morning after an overnight fast after lying down for 30 minutes
• A less strict measure is called resting metabolic rate (RMR)
• BMR = 0.9-1.2 kcal/min
  • ( 1.0 kcal/min x 60 mins x 24 hours) = 1440 kcal/day
• Males generally have higher BMRs than females

Energy Expenditure Averages

• Suggested averages from literature:

  • Females: 1400 kcal/day
  • Males: 1800 kcal/day.

• The thermic effect of food (TEF) is the energy expended to digest, absorb, transport, metabolize & store food, sometimes called diet-induced thermogenesis (DIT)

• Physical activity is any type of movement, with exercise being a specific type of PA

• Total daily energy expenditure (TDEE) = RMR + TEF + PAVEX

• Unless someone does a huge amount of PAVEx, RMR will likely be the largest component of TDEE

• To calculate daily energy needs, the BMR value is multiplied by a factor between 1.2 and 1.9, depending on physical activity level

• BMR decreases about 1-2% per decade after age 30, known as creeping obesity or middle-aged spread

• Adipose tissue mass can increase through hyperplasia and/or hypertrophy

  • Increase the size of cells as lipid is stored (hypertrophy).
  • Increase the number of cells (hyperplasia).

• Weight gain results from hypertrophy, hyperplasia, or a combination of both Obesity is characterized by hypertrophy, particularly in adults Some forms of obesity also involve hyperplasia

• Non-obese individuals have around 25 billion fat cells

• Obese individuals have around 60-80 billion fat cells

• Hyperplasia occurs mainly during growth in infancy and adolescence, but can also occur in adulthood

Set Point Theory

• The body's "ideal weight thermostat” is located in the hypothalamus
• This set point may be lowered by exercise, nicotine, and amphetamines

Role of Genetics

• Genetic influences contribute to most, if not all, cases of typical and severe obesity
• Genetics can impact appetite, metabolism, and regional fat distribution
• Many familial and cultural traits are “inherited” in a non-genetic fashion

"Thrifty Genotype” Hypothesis

• Proposed in 1962 by geneticist James Neel to explain why many Pima Indians are obese
• Populations who depended on farming, hunting, and fishing for food experienced alternating periods of feast and famine.
• To adapt to these changes in caloric needs, these populations developed a “thrifty gene” that allowed them to store fat during "times of plenty" to avoid starvation during “times of famine"
• These populations had efficient fat storage and weight gain for decreased energy intake and starvation/scarcity

Leptin

• In rodent studies, the gene found in the ob/ob mouse (obese mouse) causes excessive eating
• This is because it cannot produce the hormone Leptin, which is secreted by adipose tissue to decrease appetite when an animal is full
• The mechanism is less potent in humans than mice.
• Evidence that a defective leptin receptor increases risk for obesity
• For most individuals there is no single obesity gene, but rather a cluster of genes with an aggregate effect that leads to a higher tendency to obesity in the setting of a permissive environment

Energy Balance Equation

• 3500 excess kilocalories will be stored as 1 lb of adipose tissue
• Some research shows the obese have a higher caloric intake than non-obese.
• Obesity is more prevalent in societies with high fat diets
• Consistent finding is that when the intake of dietary fat is high in most children and adults tend to gain weight easily
• However, when intake of fat is low and intake of complex carbohydrate and fiber is higher, weight gain is less likely.

Fat Storage

• Excess protein, carbohydrate (or alcohol) can be stored as fat (lipogenesis), but it is a relatively inefficient process
• When intake of fat is high, weight gain is easy because fat is stored more easily than CHO or protein
• Fat stores are not as tightly controlled as CHO or proteinTrends

Trends in Obesity

• 1994: 29.8%
• 2000: 27.4%
• 2004: 23.7%
• 2022: 26.0%
• Missouri: 30.6%

Physical Inactivity

• Obese individuals are generally less active, and decreased physical activity relates directly to the degree of obesity
• Inactivity causes obesity, and obesity causes further inactivity

Environmental Factors

• Environmental factors suggested to decrease physical activity are

  • Reduced need for physical labor in most jobs
  • Reductions in physical activity required for daily living
  • Competition from “attractive” sedentary activities such as television, videos/DVDs, video/computer games, and internet

• The text asks: Do we live in a "toxic environment?"

• High fat, energy-dense foods, palatable, low cost, and easily available foods contribute to obesity

• Large portion sizes, decreased work-related physical activity, decreased activities of daily living, and increased sedentary behavior are contributing factors.

Individual Differences in Response to Overfeeding

• To examine these differences, a study was done with 12 pairs of young adult male monozygotic (identical) twins, none of whom were obese, with a mean age of 21 years (+/- 2)
• Subjects were overfed by 1000 kcal per day for 84 days during a 100 day period.
• The mean weight gain was 8.1 kg (17.82 lbs), and mean fat percentage increased from 11.3% to 17.8%.
• A comparable surplus of energy does not cause identical responses with respect to body weight, body compositions, or regional distribution of fat

Treatment

• To lose weight, one must decrease caloric intake, increase caloric expenditure, or both
• Goals = one-two pounds a week, or 10% total loss of initial weight in 6 months

Types of "Diets"

• Moderate deficit calorie diets are not clinically supervised with kcal limits of: women (≤1200 kcal/day) and men (≤1400 kcal/day)
• Low-calorie diets are clinically supervised with kcal limits of: women (800-1200 kcal/day) and men (800-1400 kcal/day)
• Very-low-calorie diets (VLCDs) are clinically supervised with kcal limits to ≤800 kcal/day for women and men, typically using 400-800 kcal/day (fortified shakes)

Key Points

• Gradual shifts in eating patterns and a commitment to lifestyle change, with decreased consumption of fat and simple sugars
• Increased consumption of fruits and vegetables that are high in nutrient density, complex CHO, fiber, vitamins and minerals

AACVPR Conclusions

• There is no single diet that is most successful for everyone, but a realistic approach acknowledges a wide range of success for differing amounts of: low-carbohydrate or low-fat diets for weight loss, an emphasis on high nutrient density and low energy density

• Characteristics of VLCDs (very-low caloric diet) include 0.8 to 1.5 g/kg IBW (ideal body weight) per day with ample Electrolytes and essential fatty acids

• Given a form that replaces usual food intakes, the typical duration for patients on VLCDs is 12 to 16 weeks with a rapid weight loss as a major advantage

• VLCDs are reserved for individuals with a BMI at or over 30 who haven’t been successful with other programs and psychotherapy due to stringent follow-ups such as careful instruction and follow-ups which is needed per proper use and protocol

• Patients who follow a VLCD typically lose 20 kg in 12 to 16 weeks

• Patients who have maintained a VLCD typically maintain 33% to 50% of the weight loss in the following year

• Cardiac complications including risk of sudden death, serum electrolytes need to be monitored and supplemented when necessary, and adverse reactions that are common include cold intolerance, fatigue, light-headedness, nervousness, euphoria, constipation or diarrhea, dry skin, thinning hair, anemia, menstrual irregularities

Diet Alterations

• Diet alterations are the most effective method to reduce weight and treat associated comorbidities

• Many types of weight loss and weight management programs are available, including balanced deficit diets, very-low-calorie diets, gastric bypass surgery, and pharmacotherapy

• Less than one-fourth of dieters choose to combine caloric restriction with increased levels of physical activity (300 or more minutes per week) recommended in the 2005 dietary guidelines by the US Department of Agriculture

• National Weight Control Registry: Members report that in order to maintain weight loss, they rely heavily on daily physical activity (60 minutes) eat low-calorie, low-fat foods, eat breakfast regularly, self-monitor body weight, and maintain a consistent eating pattern across weekdays and weekends”

• Optimal Program (ACSM): majority of health and weight loss benefits can be gained by physical activity of moderate intensity

• CRF Goal should be to increase activity level by 300-500 kcal/day and 1000-2000 kcal/week

• Initial Duration = 150 (30x5) min/week.

• Progression to = 300+ (60x5) min/week.

• Exercise Rx should emphasize increase of exercise duration rather than intensity

• Rating of Perceived Exertion (RPE) is 11-14

• Short bouts may be effective

• Resistance Training: 2-3 d/wk, 2-4 sets, 8-12 reps

• Programs that involve supervision or regular participation within a social group appear to be more successful in the long term

Behavior Modification

• Lifestyle modification or behavior modification interventions rely on analyzing behavior to identify events that are associated with inappropriate as well as appropriate eating, exercise, or thinking habits
• Self-monitoring with daily records of place and time of food-intake/physical activity, as well as accompanying thought and feelings, helps identify the physical and emotional settings in which eating occurs.

Benefits of Self-Monitoring

• Provides feedback on progress and places the responsibility for change and accomplishment on the patient
• Reward systems and behavior change contracts are frequently used and typically help with compliance and success
• Stimulus control involves modification of the
  • Settings or the chain of events that precede eating (antecedents)
  • Kinds of foods consumed when eating does occur
  • Consequences of eating
• Patients are taught to slow their rate of eating, to become mindful of satiety cues, and to reduce food intake

Strategies to Slow or Control the Eating Process

• Putting down the utensils between bites, chewing for a minimum number of times, pausing during meals to savor food, and delaying eating for two or three minutes to converse with others
• Serve food on a smaller plate, leave 1 or 2 bites of food on the plate, divide portions in half so that another portion can be permitted, and postpone a desired snack for 10 minutes
• A combined intervention of a calorie-deficit diet, increased physical activity, and behavioral treatment is the most successful for weight loss and maintenance
• Non-drug interventions should be attempted before drugs are considered.

Rx Weight Loss Drugs (Approved by FDA)

• Drugs should never be used alone
• Drugs are indicated of :Those whom diet, exercise, and behavior modification failed
• Should generally have some side effects and potential limited efficacy
  • (Sibutramine= Off market due to increased HR and BP)

Side Effects of Drugs

• Orlistat is an oral medication that inhibits pancreatic lipase

• Decreases fat absorption

• Lorcaserin curbs appetite

• Causes headaches, nausea, dizziness, fatigue and constipation

• Phentermine + Topiramate: curbs appetite and makes you feel full

• Causes birth defects, difficulty sleeping, constipation, mood

• Liraglutide: makes you feel full

• Causes an increase in HR, kidney problems and suicidal thoughts

• Naltrexone + Bubroprion: curbs appetite

• Causes seizure risk and suicidal thoughts

Medication Note

• Ozempic is a medicine is for adults with T2DM that alongside diet and exercise, may improve your blood sugar
• While not made FOR weight loss, it may help lose some weight
• Is a semaglutide known as wegOVy and rybelsus
• Ozempic and Wegovy are weekly injections with many side effects

Weight loss surgery

• Is an option available for patients with clinically severe obesity who haven't seen improvement through diet or exercise
• Criteria include BMI at or over 40, or BMI at or over 35 with comorbid conditions, and obesity-related physical problems that interfere with employment, walking, or family function

Gastric Bypass

• Gastric restriction or gastric bypass
• is an integrated program that must be in place before and after surgery
• Often seen as a “last resort” bariatric
• Bariatric surgery was first performed in 1954

Adjustable Gastric Banding (AGB)

• Often called "the band", AGB is a Laparoscopic Procedure

• During AGB a hollow band is placed around the stomach near its upper end

• The band creates a small pouch and a narrow passage into the larger remainder of the stomach

• The band is then inflated with a salt solution and can be tightened or loosened over time to change the size of the passage by increasing or decreasing the amount of salt solution

• Sleeve Gastrectomy (LSG) is also called "the sleeve" and is the most common procedure with Laparoscopic procedure

• LSG is where about 80 percent of the stomach is removed

• Roux-en-Y Gastric Bypass (RYGB or RNY) where a small stomach pouch is created to restrict food intake

• A Y-shaped section of the small intestine is attached to the pouch to allow food to bypass the lower stomach, the duodenum, and the first portion of the jejunum, which reduces the amount of calories and nutrients the body absorbs

Desirable Programs

• Desirable weight loss programs: food intake should be no lower than 1200 kcal/day for females and 1400 kcal/day for males
• Include variety and balance, emphasize reduction of added sugars and non-essential SFA, and foods should be readily available, easy to acquire and prepare, and taste good
• Do not promote rapid weight loss by including exercise, behavior modification, and/or emphasizing lifelong lifestyle changes
• Do not promote or sell unproven products and be dependent on special products