What is obesity?
Obesity is clinically defined as a body mass index (BMI) of 30 or higher, though BMI is an imperfect metric — body fat distribution, waist circumference, and metabolic markers provide a fuller picture. Obesity affects approximately 42% of adults in the United States and is associated with a significantly elevated risk of type 2 diabetes, cardiovascular disease, sleep apnea, certain cancers, osteoarthritis, and other chronic conditions.
Critically, obesity is not a character flaw or a simple failure of discipline. It is a chronic medical condition with well-defined biological mechanisms, including hormonal dysregulation of hunger and satiety signaling, genetic predisposition, gut microbiome differences, and the effects of prior dieting on metabolic rate. Effective treatment addresses these biological drivers, not just caloric intake.
Health effects of obesity
What drives obesity?
The fundamental cause is an imbalance between energy intake and expenditure, but this is far more complex than it sounds. Contributing factors include:
- Hormonal dysregulation — GLP-1, ghrelin, leptin, and insulin all regulate hunger and fat storage; obesity disrupts the normal feedback loops that control appetite
- Genetics — heritability of obesity is estimated at 40–70%; over 900 genetic loci influence weight
- Sleep deprivation — disrupts ghrelin and leptin signaling, increasing hunger and caloric intake
- Medications — antipsychotics, corticosteroids, insulin, beta-blockers, and antidepressants commonly cause weight gain
- Food environment — hyper-palatable, energy-dense food is widely available and actively marketed
- Stress and emotional factors — chronic stress elevates cortisol, which promotes fat storage and increases appetite
GLP-1 receptor agonists represent the most significant advance in obesity treatment in decades — producing weight loss previously achievable only through bariatric surgery.
How obesity is treated
Current evidence-based treatment combines lifestyle modification with pharmacotherapy. The most effective current medications are:
- Semaglutide (Wegovy 2.4 mg weekly): GLP-1 receptor agonist; clinical trials show average weight loss of 15–17% over 68 weeks in people without diabetes
- Tirzepatide (Zepbound): dual GLP-1/GIP agonist; trials show average weight loss of 20–22% — the highest of any current approved agent
- Bupropion/naltrexone (Contrave): oral combination; average 5–9% weight loss; useful when injectable medications are not preferred or contraindicated
- Phentermine/topiramate (Qsymia): average 8–11% weight loss; controlled substance with specific prescribing requirements
Dietary modification and physical activity remain important components. Evidence consistently shows that combination of medication and lifestyle change outperforms either alone.
Frequently asked questions
Do I qualify for GLP-1 medication?
Most people with a BMI of 30 or higher, or BMI 27 or higher with a weight-related condition such as diabetes, hypertension, or sleep apnea, meet the FDA approval criteria. The clinician will confirm eligibility and screen for contraindications.
Will I need to stay on medication forever?
Weight regain commonly occurs when GLP-1 medications are stopped, because obesity is a chronic condition with ongoing biological drivers. Like blood pressure medication, long-term use may be appropriate for many people. This is discussed as part of your care plan.
What about side effects?
Nausea, vomiting, and constipation are the most common side effects of GLP-1 medications. These are typically worst during dose escalation and improve with time. Starting at low doses and increasing slowly minimizes side effects.
Is there lab work required?
A basic metabolic panel and lipid panel are typically ordered before starting, along with HbA1c. These help establish baseline kidney function and rule out relevant contraindications. Follow-up labs are ordered periodically.