Cardiologists challenge the obsession with BMI, reveal why being ‘thin on the outside’ can mask healthy ageing and longevity: ‘Weight is easy to measure’

To get a clearer picture of long-term health, he advised tracking key indicators such as resting heart rate, blood pressure, fasting glucose and muscle mass. Monitoring these markers regularly can offer deeper insight into how efficiently the body operates and how it may perform in the years ahead. As he noted, “These metrics reveal how efficiently your system operates and how well it will perform over time.” The idea is not to dismiss weight entirely, but to place it within a wider framework of measurable factors that together shape longevity and quality of life.

Why relying on body weight or BMI can create a misleading picture of someone’s long-term health and longevity

Dr CM Nagesh, medical director and senior consultant cardiologist at Cardea Super Speciality Hospital, tells indianexpress.com, “Relying strictly on weight or Body Mass Index (BMI) is clinically flawed because these metrics cannot distinguish between muscle mass, bone density, and adipose tissue (fat).”

Dr Nagesh adds that a person with high muscle mass might be classified as “overweight” by BMI standards despite having optimal cardiovascular health. Conversely, someone with a “normal” BMI might suffer from normal-weight obesity—often called “thin outside, fat inside” (TOFI). In this state, an individual carries excess visceral fat around their internal organs. This deep fat secretes inflammatory cytokines and significantly increases the risk of insulin resistance, heart disease, and early mortality. The scale only measures gravitational pull, not metabolic function. True longevity is dictated by tissue quality and metabolic efficiency, neither of which is captured by simply weighing a patient.

How do markers like resting heart rate, blood pressure, fasting glucose and muscle mass work together?

These markers collectively map out the true efficiency of your cardiovascular and endocrine systems. “Resting heart rate and blood pressure provide a direct window into your endothelial function (the health of your blood vessel linings) and autonomic nervous system. Low values generally indicate a strong heart and flexible arteries,” notes Dr Nagesh. 

Fasting glucose reveals your cellular insulin sensitivity. When you factor in muscle mass, the clinical picture is complete. Skeletal muscle isn’t just for movement; it is an active endocrine organ and the body’s largest “metabolic sink.” Dr Nagesh states, “Greater muscle mass naturally improves insulin sensitivity by safely storing blood sugar as glycogen. Together, these metrics don’t just tell us if you are ‘not sick,’ they indicate a high metabolic reserve, meaning your body can efficiently process nutrients and withstand physical stress.”

Steps to monitor and improve these deeper health indicators over time

Dr Nagesh suggests starting by scheduling an annual metabolic panel with your doctor to baseline your fasting glucose, lipids, and blood pressure. At home, track your resting heart rate using a smartwatch, look for a steady downward trend over months as fitness improves.

“To proactively improve these numbers, prioritise resistance training at least twice a week. Building muscle creates a larger storage reservoir for blood sugar, directly lowering fasting glucose. Pair this with steady, moderate-intensity cardio to lower blood pressure and improve vascular health. Finally, protect your sleep. Chronic sleep deprivation elevates cortisol, which steadily drives up both blood pressure and insulin resistance regardless of your diet,” concludes Dr Nagesh. 

DISCLAIMER: This article is based on information from the public domain and/or the experts we spoke to. Always consult your health practitioner before starting any routine.