From ancient Greece to modern algorithms — a historical journey through the science of ideal weight
The question "What should I weigh?" has been asked for thousands of years, and the answer has changed dramatically depending on who is asking and when. The concept of an "ideal weight" is not a fixed scientific truth — it is a moving target shaped by cultural values, medical understanding, mathematical models, and evolving research. Understanding this history helps us approach the question with greater nuance and make better decisions about our own health.
The earliest recorded attempts to define an ideal human form came not from medicine, but from art and philosophy. In ancient Greece (5th–4th century BCE), the sculptor Polykleitos developed the "Canon" — a mathematical system of human proportions based on the ratio of body parts to the total height. His work "Doryphoros" (The Spear-Bearer) established a physical ideal that influenced Western art for millennia: broad shoulders, narrow waist, defined musculature, and specific proportional relationships between body segments.
Aristotle later wrote about moderation in all things, including body weight, establishing the philosophical foundation for the "golden mean" that would echo through medical thinking. But the Greeks had no concept of body fat percentage, caloric intake, or metabolic health. Their ideal was primarily aesthetic — what looked proportionate and beautiful to the eye of a sculptor.
This aesthetic approach persisted for centuries. The Roman physician Galen (129–216 CE) associated excess body weight with moral weakness, a concept that unfortunately embedded itself deeply in Western culture and still influences weight stigma today. The idea that body weight reflects character rather than biology would take nearly two millennia to dismantle.
The first systematic attempt to define ideal weight using data came from an unlikely source: life insurance companies. In the early 20th century, actuaries at Metropolitan Life Insurance Company (MetLife) began analyzing the relationship between body weight and mortality among their policyholders.
In 1943, MetLife published its first "ideal weight" tables, based on data from approximately 4 million policyholders. These tables assigned different ideal weights based on height, sex, and body frame (small, medium, large). A medium-framed man who was 5'10" was assigned an ideal weight of approximately 154–165 pounds. A woman of the same height was assigned 141–152 pounds.
These tables were groundbreaking in their use of empirical data but had significant limitations. The sample consisted entirely of white, middle-class Americans who had purchased life insurance — hardly a representative population. Furthermore, the data reflected correlation, not causation: people at certain weights happened to live longer, but the tables could not determine whether the weight itself caused the longevity or was simply associated with other health-promoting factors.
Despite these limitations, the MetLife tables became the medical standard for ideal weight assessment for nearly 50 years. Doctors referenced them during routine checkups. Magazines published them. Americans internalized specific numbers as personal targets.
The story of Body Mass Index begins not with a physician, but with a Belgian mathematician and astronomer named Adolphe Quetelet. In 1832, Quetelet developed what he called the "Quetelet Index" — a simple ratio of weight to height squared (kg/m²) — as part of his broader project to define "l'homme moyen" (the average man) through statistical analysis of human characteristics.
Quetelet never intended his index to be a health metric. He was studying population-level patterns, not individual health. His work was rooted in the emerging field of social statistics, and he explicitly cautioned against applying population averages to individuals.
For over a century, Quetelet's index languished in relative obscurity. Then, in 1972, American physiologist Ancel Keys published a paper in the Journal of Chronic Diseases titled "Indices of Relative Weight and Obesity." Keys analyzed various weight-for-height indices and concluded that Quetelet's ratio — which he renamed "Body Mass Index" — was the best available population-level indicator of obesity. The name stuck, and BMI entered the medical lexicon.
In 1997, the World Health Organization formally adopted BMI as the international standard for classifying overweight and obesity, establishing the now-familiar thresholds: underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (≥30). For the first time, there was a globally standardized framework for defining ideal weight — not as a single number, but as a BMI range corresponding to the "normal" category.
While BMI provides a range-based framework, several specific formulas have been developed over the decades to calculate an individual "ideal weight" based on height and sex. Each was created using different data and assumptions, and they often produce noticeably different results.
Developed by Dr. B.J. Devine for use in calculating medication dosages, this formula became the most widely used ideal weight calculation in clinical settings:
The formula assumes an ideal weight of 50 kg (110 lbs) for a 5-foot man and 45.5 kg (100 lbs) for a 5-foot woman, adding 2.3 kg (5 lbs) for each additional inch of height. While still commonly used, it was based on a remarkably small and non-representative sample and tends to produce lower values than many other formulas.
Dr. J.D. Robinson modified the Devine formula after observing that it tended to underestimate ideal weight:
The Robinson formula uses a higher base weight and a slower rate of increase per inch, which produces higher estimates for taller individuals and more moderate estimates overall.
Dr. D.R. Miller proposed another modification, this time with an even higher base weight:
The Miller formula produces the highest estimates among the height-based formulas, which some argue better reflects modern nutritional standards and body compositions.
Developed by Dr. G.J. Hamwi for quick clinical estimation:
The Hamwi formula also incorporated body frame adjustments: ±10% for large or small frames. While simple, it was designed for rapid bedside estimation rather than precision.
For a 5'10" (178 cm) man, the different formulas produce ideal weight estimates spanning a 22-pound range:
| Formula | Ideal Weight (lbs) | Ideal Weight (kg) |
|---|---|---|
| Devine | 160.6 | 72.9 |
| Robinson | 164.4 | 74.6 |
| Miller | 170.5 | 77.4 |
| Hamwi | 161.6 | 73.3 |
| BMI 22 (mid-range) | 153.0 | 69.4 |
This 22-pound range highlights a fundamental truth: there is no single "correct" ideal weight. Each formula captures a different statistical relationship between height and weight, and none accounts for the individual variables that actually determine what weight is healthy for a specific person.
In the 21st century, the concept of ideal weight is undergoing its most significant evolution yet. Modern health science increasingly recognizes that a single number — whether from a formula, a table, or a BMI calculation — cannot capture the complexity of what constitutes a healthy weight for an individual.
Several key insights have driven this shift:
Two people at identical weights can have vastly different health profiles. A person at 180 lbs with 12% body fat and significant muscle mass has very different metabolic health markers than a person at 180 lbs with 30% body fat. Modern assessment prioritizes body composition — the ratio of fat mass to lean mass — over total weight.
Where your body stores fat is as important as how much you carry. Visceral adipose tissue (fat stored around abdominal organs) is strongly associated with insulin resistance, inflammation, and cardiovascular disease. Subcutaneous fat (stored beneath the skin) carries far fewer metabolic risks. Two individuals with the same body fat percentage but different fat distribution patterns can have dramatically different health outcomes.
The concept of "metabolically healthy obesity" — individuals with BMI above 30 who have normal blood pressure, blood sugar, and lipid profiles — has challenged the assumption that higher weight automatically means poorer health. Research published in Diabetes Care (2022) found that approximately 20–30% of individuals classified as obese by BMI are metabolically healthy, while 15–20% of individuals in the "normal" BMI range have metabolic abnormalities.
Rather than pursuing a specific number, modern health organizations increasingly advocate for a "healthy weight range" — a band of weights within which an individual can maintain normal metabolic function, adequate energy, and good quality of life. This range is personal and depends on factors that no formula can capture: genetics, bone structure, muscle mass, hormonal profile, age, and lifestyle.
Perhaps the most important modern insight is that the "ideal" weight is one you can maintain sustainably. Research consistently shows that weight cycling (repeatedly losing and regaining weight) is more harmful to health than maintaining a stable weight that is slightly above the "ideal" range. A weight you maintain comfortably for years is healthier than a lower weight you achieve through extreme restriction and cannot sustain.
Given this complexity, how should you approach the question of ideal weight? Here is a framework that incorporates modern understanding:
The concept of ideal weight has evolved from aesthetic proportions in ancient Greece, through actuarial tables based on insurance data, to mathematical formulas and BMI-based ranges, and now toward a more nuanced understanding that prioritizes individual health over statistical norms. This evolution is not a sign of failure — it reflects the progress of science in acknowledging human complexity.
The best answer to "What should I weigh?" in 2026 is not a number from a formula or a range from a chart. It is a weight at which your body functions well, your metabolic markers are normal, you have the energy and strength to do the things you enjoy, and you can maintain that weight without sacrificing your quality of life. That weight will be different for every person, and it may change throughout your life. And that is perfectly fine.
No single formula is universally "most accurate" because ideal weight depends on individual factors like body frame, muscle mass, age, and health status. The Devine formula is most commonly used in clinical settings, the Robinson and Miller formulas are considered reasonable updates, and the BMI-based range (18.5–24.9 BMI) provides the broadest accepted framework.
Each formula was developed using different population data and mathematical approaches. The Devine formula was based on a small sample of patients, the Hamwi formula was designed for quick clinical estimation, and BMI-based calculations use statistical population norms. Differences of 10–20 pounds between formulas are common.
Yes. Research shows that a slightly higher weight in older adults (65+) is associated with better outcomes, including lower mortality risk and better bone density. The concept of ideal weight should be adjusted for age, with higher acceptable ranges for older populations.
Body frame size (small, medium, large) can account for a difference of 10–15% in ideal weight estimates. People with larger frames naturally carry more bone and muscle mass. Frame size is typically estimated by measuring wrist circumference relative to height.
Modern health science increasingly favors the concept of a "healthy weight range" rather than a single ideal number. Health depends on body composition, fat distribution, metabolic markers, physical fitness, and mental well-being — not a single number on a scale. The best weight for you is one where you feel healthy, have normal metabolic markers, and can maintain sustainably.