The risk of cardiovascular disease (CVD) is often increased in patients affected by obesity. However, in certain patients with obesity, the risk of CVD is reduced compared to similar cohorts with a normal body mass index. This anomaly is often referred to as the obesity paradox and demonstrates that an increased BMI provides mortality benefits in some individuals, thus illuminating the limitations of using BMI as the sole predictor for health and CVD risk. For example, if a patient with a BMI of 33 kg/m² goes to the gym 5 days per week, they will likely lower their CVD risk compared to a sedentary person with a BMI of 25 kg/m².

In fact, the mindset of those with excess weight may play a role. For example, a person with a normal BMI may justify eating poorly or a lack of exercise simply because they feel protected with their normal BMI. In contrast, a patient with obesity may be more aware of their risks and thus engage in healthy compensatory behaviors, which can improve their overall outcomes.

Although BMI does not solely account for cardiovascular risk, it does have many direct correlations:

  • Mortality: A BMI between 25-35 kg/m² reduces life expectancy by 2-4 years and a BMI of 40-45 kg/m² by 8-10 years (similar to smoking).
  • Heart failure: Risk increases 2-fold with a BMI ≥30 kg/m².
  • Atrial fibrillation: For every ↑ 1 unit of BMI, risk increases by 4%.
  • Type 2 diabetes: 80% of cases are directly related to obesity.
  • Cerebral vascular accident: For every ↑1 unit BMI, there is an increase in ischemic stroke by 4% and hemorrhagic stroke by 6%.
  • Sleep apnea: BMI >30 kg/m² incurs a 30% risk of sleep apnea.

The distribution of adipose tissue is another important indicator of CVD risk. Visceral (fatty tissue infiltrating organs) or truncal obesity incurs a higher CVD risk than subcutaneous adiposity. In fact, in patients with a BMI in the moderate range (25-35 kg/m²), cardiovascular risk is better predicted by waist circumference or waist-to-hip ratio than BMI alone, as these are markers for the visceral distribution of adiposity. Therefore, the highest cardiovascular risk is found in those with an increased waist circumference but a normal-range BMI.

To summarize, on a population level, obesity generally incurs an increased risk of mortality and morbidity and is associated with over 230 comorbidities, including malignancies. In contrast, physically fit people will have a better long-term outcome, especially in the moderate BMI range. Those with a normal BMI with increased waist circumference (central obesity) tend to have the highest risk of cardiovascular disease. In addition, remember that both extremes of BMI have higher mortality rates. Whether visceral or subcutaneous, fatty tissue can cause fat mass disease leading to osteoarthritis, sleep apnea, etc. However, fatty tissue can also have some potential benefits (stored energy in cachectic states, thermal benefits, and protection from trauma), which may contribute to the paradox. This will likely be the highest-yield information to keep in mind for boards. Although there are other reasons and theories on why BMI does not follow the rules, these likely will not be testable unless confirmed.

Now onto debunking 5 myths related to obesity:

  • Obesity is caused by a lack of willpower: This is equivalent to “eat less, move more” to lose weight. Obesity is a chronic, complex disease that is influenced by many factors, including environment, dysregulation in neurohumoral and endocrine pathways, epigenetics, etc. Understanding that obesity is a chronic disease just as lupus, alcohol use disorder, or hypertension are chronic diseases, allows the realization that it is not just a lack of willpower.
  • Anti-obesity medications and metabolic and bariatric surgery (MBS) are the easy ways out: Patients with obesity pursuing MBS must adhere to rigorous guidelines and complete numerous preoperative checklist items. Obesity is a disease, and long-term treatment is necessary, just as with any other chronic disease. The pillars of diet and physical activity are still pursued despite medications or surgery.
  • Low fat/keto/Atkins, _____ is the best diet: No specific diet is the single answer to weight loss. Similarly, no medication or one surgery is the sole answer for an individual patient. Many studies have shown that the best dietary plan is one that patients can adhere to longitudinally.
  • For every 3500 calories reduced, you will lose 1 lb: Our bodies are not calorimeters. This myth does not account for factors such as genetics, neurohormonal balances, metabolic rate, energy harvesting, and the microbiome.
  • Slow and steady wins the race: Actually, those with rapid weight loss tend to maintain longer-term weight deficits compared to slower weight loss. The reasoning is likely multifaceted, including early-onset motivation, fewer joint pains (improving physical activity levels), and increased awareness of the complications that come with weight regain. Often a goal of losing 5% of weight over 3 months and 10% over 6 months is better than pursuing a goal of 5-10 lb per year.

Importantly, our mindset towards obesity will not change unless we are aware of the myths that are out there. In addition, we need to be able to defend why working towards improved cardiovascular health through weight loss and physical activity is important and combat when the obesity paradox is used as an excuse for not pursuing health.

Sample Question

A group of physicians are developing a program to address patients with coronary artery disease who are at the highest risk of mortality within the next five years. To simplify the program, they only evaluate the body mass index and waist circumference. Those with the highest mortality risk will be entered into an intensive physical, dietary, and behavioral modification program. Which of the following parameters of patients should receive priority entrance into this class?

A. BMI 22 kg/m²; Waist circumference 85 cm

B. BMI 22 kg/m²; Waist circumference 101 cm

C. BMI 26 kg/m²; Waist circumference 85 cm

D. BMI 30 kg/m²; Waist circumference 85 cm

E. BMI 30 kg/m²; Waist circumference 101 cm

Next Week: Epigenetics

Upcoming: Dietary plans (Mediterranean/DASH, etc.)

For more practice questions, check out the following:

  • Obesity Medicine Board Review Questions (2026): Qs 52 and 114.
  • Obesity Medicine Practice Tests (2026)

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