Why "ideal" bodies keep changing
The strongest pattern in the evidence is that body ideals are socially constructed rather than biologically fixed. Sociocultural theories hold that different societies carry different conceptions of the ideal body shape, and in contemporary Westernized cultures advertising, the internet, and social media push particular archetypes of "beauty" that are treated as having superior social value [3]. Those promoted ideals are often entirely unrealistic, and chasing them is linked to body dissatisfaction, appearance anxiety, low self-esteem, and depressive symptoms [3].
The ideal is also not stable within a culture. Research on the female body describes an "evolving ideal body imaginary" that is reproduced and recycled at individual, social, and global levels [4], and work on male body image treats ideals of the muscular male body as something that evolves over time rather than a fixed target [5]. If the standard moves with the society that holds it, it cannot also be a single evolutionary endpoint.
Even clinical "ideal weight" is a rough shortcut
The medical notion of an Ideal Body Weight (IBW) sounds authoritative, but it was derived from anthropometric measurements of life-insurance policy holders collected between 1885 and 1908, organized by sex and age [2]. The formulas assume weight rises as a linear function of height, yet weight also depends on body volume — width, trunk length, and musculature — and the measures ignore comorbidities and genetics [2].
That matters because IBW is still used in practice: to plan tube and intravenous feeding, avoid malnutrition, guide weight management, decide transplant eligibility, and include or exclude people from research studies [2]. The commentary's conclusion is that every individual has a distinct "ideal" body weight shaped by genetics, environment, and lifestyle [2] — a personalized target, not a universal one.
Does body shape carry an evolutionary signal at all?
One line of work does look for an evolutionary angle on body shape, but narrowly. In a sample of 102 women aged 35–55, researchers examined waist measurements in relation to the sex ratio of their children, building on evidence that testosterone levels in women are correlated with a tendency to produce sons [1]. This treats a specific female body measure as potentially linked to reproductive outcomes — it does not establish a single ideal body for the species, and the abstract reports only the setup and sample, not a confirmed universal standard [1].
So the evolutionary evidence is best read as a possible link between one body measurement and one reproductive outcome in one sample, not as a blueprint for an ideal form. The cultural and clinical evidence points the other way: ideals are local, shifting, and individual [2][3].
What should a curious reader conclude?
If you are looking for the body evolution "designed" for you, the honest answer is that there is no single template to match. Body ideals vary by society and change over time [3][4], media portrayals shape what people aspire to in ways that can harm body image [3][5], and clinical weight standards are acknowledged to be imperfect shortcuts that miss genetics and body composition [2].
The practical implication is to treat any claimed "ideal" with suspicion about its source. A number attached to a height, a waist measurement, or a media archetype is a convention or a correlation, not a biological mandate — and the evidence supports individualized targets over universal ones [2].
Sources used in this answer
Women's waists and the sex ratio of their progeny: evolutionary aspects of the ideal female body shape
In 102 women aged 35–55, the study examined waist measurements in relation to offspring sex ratio, framed around an 'ideal' female body shape and evidence linking women's testosterone levels to a tendency to produce sons.
Ideal body weight: A commentary
The Ideal Body Weight model derives from 1885–1908 life-insurance data, assumes weight scales linearly with height, ignores comorbidities and genetics, and is imperfect; each individual's ideal weight is distinct based on genetics, environment, and lifestyle.
The Ideal of the Perfect Body
Sociocultural theories hold that ideal body shapes differ across societies, and Westernized media promote unrealistic beauty archetypes that can drive body dissatisfaction, anxiety, low self-esteem, and excessive behaviors such as compulsive exercise and image-enhancing drug use.
Beyond the Westernized Body: Constructing the Ideal Female Body Through Paradoxical Paradigms
The paper examines how an evolving ideal female body imaginary is constructed and reproduced through cultural and social paradigms at individual, social, and global levels.
The media's representation of the ideal male body: A cause for muscle dysmorphia?
The paper examines how media representations of muscular men relate to men's perceptions of their actual and ideal body shape, in the context of evolving ideals of male body image.