Obesity presents a multifaceted and pressing health concern that has increasingly captured global attention in recent years.
Obesity is defined by the substantial buildup of excess body fat, resulting in a myriad of health complications that impact both individuals and the healthcare systems that serve them.
This condition transcends boundaries of age, socioeconomic status, and cultural backgrounds, manifesting as a widespread epidemic that impacts communities worldwide. The repercussions of obesity extend beyond its influence on physical well-being, as it is intricately linked to a range of comorbidities such as diabetes, cardiovascular diseases, and mental health disorders. As a result, addressing obesity has become paramount in the realm of public health, necessitating a comprehensive understanding of its origins, consequences, and evidence-based strategies for prevention and management.
DIAGNOSIS OF OBESITY
To diagnose obesity, both BMI measurement and clinical assessment of weight-related complications are recommended.
Classifications for obesity are as follows:
Class 1 obesity ranges from a BMI of 30 kg/m2 to 34.9 kg/m2
Class 2 obesity from 35 kg/m2 to 39.9 kg/m2
Class 3 obesity is indicated by a BMI of at least 40 kg/m2
However, factors like age, sex, hydration level, muscle composition, the presence of fluid in noncirculatory spaces, sarcopenia, edema, and high-volume tumors should be considered before assigning a classification. These classes are sometimes called mild, moderate, and severe obesity.
Waist circumference should also be considered in patients with BMIs between 25 kg/m2 and 35 kg/m2. Waist circumferences of at least 102 cm in men and 88 cm in women suggest abdominal obesity, associated with an increased risk of adiposity-related diseases. Lower thresholds may be used outside the United States, and region-specific points may also be applied based on ethnicity. For example, in individuals of South Asian, Southeast Asian, and East Asian heritage, a waist circumference of at least 85 cm in men and 74 cm to 80 cm in women may indicate abdominal obesity.
Clinical assessments for weight-related complications are crucial for patients with overweight or obesity. Screening should cover prediabetes, type 2 diabetes mellitus, dyslipidemia, hypertension, metabolic syndrome, cardiovascular disease, nonalcoholic fatty liver disease, osteoarthritis, mental depression, obstructive sleep apnea, asthma, reactive airway disease, gastroesophageal reflux disease, urinary incontinence (for women), and reproductive abnormalities (for premenopausal women). It's also important to inform women about their increased risk of infertility, lower success rates for assisted reproduction, and the correlation between higher BMI and gestational diabetes and other obstetric and fetal complications.
To establish prevention and treatment goals, assessing an individual's weight, lifestyle, and medical history is essential.
For those with a standard (healthy) weight (BMI between 18.5 and < 25 kg/m2), counselling should focus on avoiding weight gain. Individuals at high risk of being overweight or obese due to genetics, biomarkers, family history, ethnicity, cultural practices, or behaviours should receive counselling on weight gain avoidance and education on healthy meal planning and physical activity.
Individuals with a BMI of 25 kg/m2 or higher should undergo an evaluation for weight-related complications to establish personalized goals for prevention and treatment. The AACE/ACE guidelines employ a staging system incorporating BMI and the complications' presence, extent, and severity to set treatment targets.
Patients in the overweight stage 0 should aim to avoid any further weight gain or lose weight to avoid progression to obesity and complications.
For patients with obesity, readiness to make lifestyle changes should be assessed. Those ready should work with clinicians to set weight loss goals and complementary lifestyle treatment strategies. Plans for overweight stage 0 include weight loss or prevention of additional weight gain while preventing complications. Weight loss is recommended for patients in obesity stage 1 or stage 2. However, the AACE/ACE guidelines provide complication-specific treatment targets. In contrast, the ACC/AHA/TOS guidelines recommend determining weight-loss goals in collaboration with the patient rather than solely based on weight-related complications.
To mitigate the burden of weight-related complications, both guidelines advise patients in obesity stage 1 or stage 2 to aim for a minimum weight loss of 5% of their body weight. The AACE/ACE guidelines suggest losing at least 10% for many complication-specific targets. Early weight loss is encouraged, with a target of 2.5% weight loss within one month for all patients with overweight or obesity, according to the AACE/ACE guidelines. The ACC/AHA/TOS guidelines suggest a realistic goal of 5% to 10% weight loss within six months.
Obesity treatment necessitates collaboration between committed patients and informed clinicians. Caloric intake reduction forms the basis of weight loss, with aerobic exercise, resistance training, and a reduced-calorie diet recommended for those aiming to lose weight. Behavioural interventions should also be pursued to enhance adherence to physical activity and meal plan recommendations. These interventions may include individual activities like goal setting and self-monitoring, one-on-one sessions with clinicians for cognitive behavioural therapy and dietary education, and group meetings for peer support. For patients who do not achieve 2.5% weight loss within one month, the AACE/ACE guidelines suggest escalating behavioural interventions
A structured and comprehensive lifestyle intervention program for weight loss, encompassing a healthy meal plan, physical activity, and behavioural intervention, is recommended for all patients with overweight or obesity seeking to lose weight. High-intensity, in-person programs with 14 or more sessions in 6 months are considered the most effective, producing an average weight loss of 5% to 10%. Alternative programs, including internet- or phone-based options or referral to a nutrition professional, may be prescribed when in-person programs are unavailable. Calorie-restricted diet, physical activity prescription, and behavioural lifestyle intervention should be tailored to each patient to improve adherence and outcomes.
When combined with lifestyle modifications, pharmacotherapy leads to more significant and sustained weight loss than alone. The AACE/ACE guidelines recommend this combination for individuals with a BMI of at least 27 kg/m2 if lifestyle therapy fails to halt weight gain, especially for those with obesity stage 2. The selection and use of anti-obesity medications (AOMs) should be individualized, considering clinical weight loss goals, weight-related conditions, and drug cautions and warnings.
Several medications are FDA-approved for long-term obesity treatment, including orlistat, phentermine-topiramate, naltrexone-bupropion, liraglutide, and lorcaserin. Semaglutide injection of 2.4 mg subcutaneously once weekly is also approved for chronic weight management.
The AGA guideline recommends considering AOMs for adults with obesity who have had an insufficient response to lifestyle intervention alone. Semaglutide 2.4 mg is favoured by the AGA guideline authors due to its substantial net benefit. The guideline advises against the use of orlistat.
For short-term weight loss, four drugs are available in the United States: phentermine, benzphetamine, diethylpropion, and phendimetrazine.
While the AACE/ACE guidelines recommend against their use, the Endocrine Society guideline considers off-label use of phentermine for long-term obesity treatment. Phentermine has a relatively low cost, low addiction potential, demonstrated efficacy and safety, and is widely prescribed. However, its prescription should be contingent upon specific conditions being met. The AGA guideline also provides a qualified endorsement of long-term phentermine prescription, acknowledging low-quality evidence for this recommendation.