🍽️nutrition assessment review
9.4 Obesity and Overnutrition Assessment
6 min read•Last Updated on July 30, 2024
Obesity is a complex chronic disease characterized by excessive body fat accumulation. This section explores how to define, classify, and assess obesity using tools like BMI, body composition analysis, and waist circumference measurements.
Understanding obesity's impact on health is crucial. We'll examine the metabolic and cardiovascular risks associated with obesity, as well as dietary patterns and behaviors that contribute to overnutrition. Finally, we'll discuss evidence-based interventions for managing obesity.
Obesity definition and classification
Defining obesity as a chronic disease
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- Obesity is a complex chronic disease characterized by excessive body fat accumulation that presents a risk to health
- Results from a sustained positive energy balance leading to weight gain over time
Using body mass index (BMI) to classify obesity
- Body mass index (BMI) is a person's weight in kilograms divided by the square of their height in meters (kg/m2)
- Used to screen for overweight and obesity in adults
- World Health Organization (WHO) classifies obesity based on the following BMI ranges:
- Overweight: BMI greater than or equal to 25 kg/m2
- Obesity class I: BMI 30.0 to 34.9 kg/m2
- Obesity class II: BMI 35.0 to 39.9 kg/m2
- Obesity class III: BMI greater than or equal to 40 kg/m2
- BMI is an indirect measure of body fat that does not account for body composition, age, sex, or fat distribution
- May overestimate body fat in athletes with high muscle mass
- May underestimate body fat in older persons or those with low muscle mass
Body composition and fat distribution
Assessing body composition in obesity
- Body composition refers to the relative proportions of fat and fat-free mass in the body
- Excess body fat, particularly abdominal fat, is associated with increased health risks in obesity
- Skinfold thickness measurements estimate subcutaneous body fat at specific body sites using calipers
- Sum of skinfolds or equations predict body fat percentage and assess total body fatness
- Bioelectrical impedance analysis (BIA) measures the body's resistance to a small electrical current
- Estimates total body water, fat-free mass, and body fat percentage
- Requires specific conditions for accurate results
- Dual-energy X-ray absorptiometry (DXA) is a gold standard method
- Uses low-dose X-rays to measure total and regional body composition, including bone mineral density, lean soft tissue, and fat mass
Measuring abdominal obesity and fat distribution
- Waist circumference is a simple measure of abdominal obesity
- Stronger predictor of obesity-related health risks than BMI alone
- Waist circumference cut-points of >102 cm in men and >88 cm in women indicate increased disease risk
- Waist-to-hip ratio (WHR) assesses body fat distribution by dividing waist circumference by hip circumference
- WHR >0.90 in men and >0.85 in women is associated with increased metabolic and cardiovascular disease risk
Metabolic and health risks of obesity
Insulin resistance and type 2 diabetes
- Insulin resistance is a central feature of obesity that can progress to prediabetes, metabolic syndrome, and type 2 diabetes mellitus
- Excess adiposity, particularly visceral fat, impairs insulin signaling and glucose uptake
Cardiovascular disease risk factors
- Dyslipidemia in obesity is characterized by:
- Elevated triglycerides
- Low high-density lipoprotein (HDL) cholesterol
- Small dense low-density lipoprotein (LDL) particles that increase atherosclerotic cardiovascular disease risk
- Hypertension is more prevalent in individuals with obesity
- Due to increased sympathetic nervous system activity, insulin resistance, and salt retention
- Obesity-related hypertension increases the risk of cardiovascular and kidney disease
Other obesity-related health conditions
- Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver conditions associated with obesity
- Ranges from simple steatosis to non-alcoholic steatohepatitis (NASH) and cirrhosis
- Obstructive sleep apnea (OSA) is a sleep disorder characterized by repeated upper airway collapse during sleep
- Leads to intermittent hypoxia and sleep fragmentation
- More common in obesity and increases the risk of cardiometabolic complications
- Obesity is associated with an increased risk of certain cancers
- Including colorectal, breast (postmenopausal), endometrial, kidney, pancreatic, and liver cancer
- Mechanisms may involve chronic inflammation, insulin resistance, and hormonal imbalances
Dietary patterns in overnutrition
Western dietary pattern and obesity risk
- Western dietary pattern is characterized by:
- High intake of refined grains, added sugars, unhealthy fats, red and processed meats
- Low intake of fruits, vegetables, and whole grains
- Associated with an increased risk of obesity and related chronic diseases
Specific dietary factors contributing to overnutrition
- Sugar-sweetened beverages (SSBs) are a significant source of added sugars and excess energy intake
- Regular consumption of SSBs is associated with weight gain, type 2 diabetes, and cardiovascular disease
- Portion sizes of foods and beverages have increased over time, contributing to excess energy intake
- Larger portion sizes, particularly of energy-dense foods, can lead to overconsumption and weight gain
- Frequent consumption of fast food and meals away from home is associated with:
- Higher energy intake
- Poorer diet quality
- Increased risk of obesity
- These meals tend to be higher in calories, saturated fat, and sodium, and lower in fruits, vegetables, and whole grains
Eating behaviors and overnutrition
- Mindless eating, or eating while distracted by television, smartphones, or other activities
- Can lead to overconsumption and reduced awareness of hunger and satiety cues
- Mindful eating practices may help improve portion control and reduce overeating
- Emotional eating, or eating in response to negative emotions or stress
- Can contribute to overnutrition and weight gain
- Developing alternative coping strategies and practicing mindfulness can help manage emotional eating behaviors
Interventions for managing obesity
Lifestyle modification as the foundation
- Lifestyle modification, including a combination of diet, physical activity, and behavioral strategies, is the foundation of obesity management
- Modest weight loss of 5-10% of initial body weight can improve obesity-related comorbidities
Dietary interventions for weight loss
- A calorie-reduced diet that achieves an energy deficit of 500-750 kcal/day can lead to a weight loss of 1-2 pounds per week
- Individualized calorie targets based on age, sex, weight, and physical activity level can promote sustainable weight loss
- Dietary patterns emphasizing whole foods can improve diet quality and support weight management
- Examples include the Mediterranean, DASH, and plant-based diets
- These diets focus on fruits, vegetables, whole grains, lean proteins, and healthy fats
Physical activity recommendations
- Regular physical activity is essential for weight loss and maintenance
- The American College of Sports Medicine recommends:
- 150-250 minutes per week of moderate-intensity aerobic activity for weight loss
- Higher levels (>250 minutes/week) for weight loss maintenance
- Resistance training at least twice per week can help:
- Preserve lean body mass during weight loss
- Improve body composition, metabolic health, and functional capacity
Behavioral strategies and pharmacotherapy
- Behavioral strategies can enhance adherence to lifestyle changes and support long-term weight management
- Examples include goal setting, self-monitoring, problem-solving, and stimulus control
- Pharmacotherapy may be considered for individuals with:
- BMI ≥30 kg/m2 or BMI ≥27 kg/m2 with obesity-related comorbidities
- In conjunction with lifestyle modification
- Medications such as orlistat, liraglutide, or phentermine/topiramate can enhance weight loss and improve cardiometabolic risk factors
Bariatric surgery for severe obesity
- Bariatric surgery may be considered for individuals with:
- Severe obesity (BMI ≥40 kg/m2 or BMI ≥35 kg/m2 with comorbidities)
- Who have not achieved durable weight loss with nonsurgical methods
- Surgical procedures such as Roux-en-Y gastric bypass or sleeve gastrectomy can lead to:
- Significant and sustained weight loss
- Remission of comorbidities
- Improved quality of life