Aging as seen by body indices

The LIFE-ADULT cohort included 10,000 participants sampled from the population of Leipzig. This cross-sectional study covers an age range from mid-age (about 40 years) up to elderly (80 years) men and women. Basic characteristics of the sampling are summarized in Table 1. 3D body scanning data is available for 8499 participants, which were stratified by sex and age to estimate the alterations of “classical” anthropometrical characteristics (body height, weight, BMI, and waist-to-hip circumference ratio (WTH)) upon aging (Fig. 1). Body heights of both sexes start to decrease from an age of about 50 years. The lower quantile of body height in younger participants (<50 years) approximately corresponds to the upper quantile in older ones (>70 years). The weight of the participants alters in an opposed fashion. It increases with age up to 55–59 years, and then it declines. Combination of height and weight results in increasing BMI values up to about 60 years and virtually invariant BMI values for older people. Such a levelling off behavior of BMI at about 60 years followed by a slight decay was found also in other studies and seems to reflect rather aging-related physiological changes than changes of lifestyle (e.g., due to retirement)21,22,23.

Table 1 Basic characteristics of the LIFE-ADULT study population. Full size table

Fig. 1: Classical anthropometric measures as a function of age. a Body height, b weight, c BMI, and d waist-to-hip circumference ratio are given as violin plots stratified by sex and age, respectively. Dashed horizontal lines refer to mean values for women and men, respectively. e The overall distribution of participants classified as underweight (BMI <18.5), normal weight (18.5 ≤ BMI < 25), overweight (25 ≤ BMI < 30), and obese (BMI ≥30) according to WHO classification53. f BMI categories stratified by age. Full size image

BMI curves of both sexes are very similar; however, men show a slightly higher mean BMI than women. The age dependency of WTH resembles that of BMI, where, however, men show typically markedly higher values compared to women. Among people older than 50 years, more than 50% show an “apple-like” body shape (WTH ≥0.8 and 0.9 in women and men, respectively), which is found to associate with higher health risk24.

The body indices remain, on average, virtually invariant for women and men older than 60 years, which makes them unsuitable to discriminate age-dependent trends for elderly people.

Overall, about 21–23% of women and men are obese, while a markedly higher fraction of about 45% of men are overweight compared with 32% of women. The relative amount of obese people increases with age, while that of normal weight ones decreases mainly up to an age of about 60 years. More than 25% of participants older than 60 years are obese (BMI ≥30). In summary, standard body indices reflect typical alterations of body dimensions upon aging, such as decreasing body height and increasing WTH, sex specifics, and also deviations from linear changes as, for example, observed for elderly people. Especially WTH, but also BMI, show sex-specific differences with relation to obesity. In summary, we find age-related trends of decreasing body height and weight. This single-feature related anthropometrical information is however relatively rough and not sufficient for a detailed evaluation of changes of the body shape upon aging.

Aging body shapes

Next, we analyzed age-related alterations of the body meta-measures, which distribute virtually over all parts of the body (Fig. 2a). Most of them positively correlate with age (Pearson’s correlation coefficients between 0.2 and 0.5, whereby correlation is stronger for women than for men in most cases, Fig. 2b). In contrast, thigh girth and upper body lengths decrease with age on the average as indicated by negative correlation coefficients.

Fig. 2: Alterations of body measures with age. a Assignment of the 13 meta-measures defined previously. b Correlation of the meta-measures with age visualized as polar diagram. The black polygon refers to r = 0. c The “bodygram” visualizes the meta-measures in Z-units as a polar diagram. The black polygon refers to Z = 0. Mean bodygrams of male and female participants averaged over all ages (left part) and after stratification into age decades (right part) reveal gender-specific differences and age-dependent changes of the meta-measures. Difference Δ-bodygrams visualize the changes of the meta-measures between the 40–49 and 70–80 years intervals. The green and red arrows in the left part highlight the most pronounced differences (ΔZ >±0.2). Full size image

For visualization of the meta-measures and of their changes, we use a polar diagram termed “bodygram,” where each axis refers to one meta-measure (Fig. 2c). The bodygrams reveal marked sex-specific differences such as larger dimensions of the upper body (meta-measures H–M) in men, and larger girth and length dimensions of the legs (meta-measures C and F) in women (Fig. 2c, left part), meaning that the leg measures were larger in women in relation to their body height. For an age-dependent view, we generated mean bodygrams averaged over decadal age intervals (Fig. 2c, right part), and difference bodygrams between the youngest (40–49 years) and oldest (70–80 years) strata (Fig. 2c). Interestingly, these Δ-bodygrams are very similar for women and men, indicating similar changes of the body measures upon aging despite the distinct gender specifics of the bodygrams. In correspondence with the correlation analysis, we found that all meta-measures increase upon aging, except for meta-measure H estimating upper body lengths. These opposite trends indicate reshaping of the body towards a smaller torso in relation to body size in older individuals. The increasing meta-measures collect mainly girth measures, reflecting a gain of body volume and weight as discussed above. Other meta-measures such as J and L (neck length and arm girths, respectively) markedly increase in women, while C (thigh girth) increases typically in men. The latter alterations reflect redistributions of body mass from legs towards the torso, or, in other words, the shift from a pear-like towards an apple-like body shape.

Overall, we documented alterations of the anthropometrical meta-measures extracted from 3D body scanning. They reflect marked sex-specific differences of the body shapes as expected, especially the broader upper male body and the larger dimension of female legs. At the same time, we see similar reshaping trends upon aging in both sexes, namely increasing body girths and a (relative) shortening of the upper body.

Aging body types

In the next step, we aimed to describe age-related alterations of the 15 body types identified previously to describe the heterogeneity of body shapes observed in the population of Leipzig18 (see also Supplementary Fig. 1). Each of the body types collects different age strata of participants showing, however, large variances and broad mutual overlaps (Fig. 3a). We ordered the body types with increasing mean age of their members. Female body types (F-types) show a broader range of mean ages, whereas male body types (M-types) are more uniform. The gender-unspecific (B) body types collect either younger (B1) or older (B2) people and were considered separately for women (B1F, B2F) and men (B1M, B2M). Variability of M-types is higher than that of female ones, except for F3, which collects overweight and obese women of all ages. Age-related changes of BMI are small compared to variabilities of the body types (see below and Supplementary Fig. 2). Two F-types (F3 and F4) and one M-type (M5) collect mainly obese individuals (BMI >30 kg/m2). Interestingly, the WTH ratios do not reflect obese characteristics of these body types compared with the other, non-obese ones. Body types F5, F6, B2M, and M7 collect the highest fractions of people older than 70 years (Supplementary Fig. 1).

Fig. 3: Anthropometric parameters of the body types. a The age dependence of F-types (F1–F6) is more pronounced than that for men (M1–M7). b, c F3 and F4 are obese types among the F-types with a high variability of F3, while M5 is the most obese M-type. d The WTH data do not reflect these characteristics. P values of differences between the body types groups and age-matched reference groups are indicated as signs in the head line of each plot (p < 0.1 (+/−), <0.01 (++/–), and <0.001 (+++/−−−). Full size image

Detailed bodygram analysis of the different body types reveals type-specific changes upon aging, where a part of them is characterized by increasing values of the meta-measures, while others are dominated by decreasing or virtually age-invariant meta-measures (Supplementary Fig. 6). The shoulder angle, for example, increases with age, leading to more hanging shoulders for older people. Also, chest and arm lengths are growing measures reflecting the relative increase of the upper body. Decrease of the dimensions of the lower part of the body is reflected by decreasing thigh girths in men. Overall, aging body types are characterized by the shift of body proportions towards a larger upper part and smaller legs, which become relatively short and lean. Some of the meta-measures reveal gender-specific alterations, such as upper body girths, which increases typically in the M-types reflecting the shift into apple-like body shapes. Other meta-measures, for example, arm length, arm girths, neck girth, and neck length specifically change in F-typess and partly reflect the increase of the upper body’s size. In general, F-types seem to underlie stronger changes than male ones.

Table 2 summarizes the characteristic body shape changes observed. The major characteristics of the body types are virtually age independent. They maintain and partly amplify their most prominent characteristics in elderly people. For example, body types with tall and lean shape (B1, F1, and M2) become longer and/or leaner (longer chest and upper body). Moreover, men with a broad neck (M4 and M7) keep this property, and participants with a massive upper body (F3 and M5) additionally get leaner legs. Overall, these results indicate that, upon aging, slim body shapes remain slim and partly tend to become even more lean and fragile, while obese body shapes remain obese. For most of the body types, we observe sex-independent changes upon aging as described in the previous subsection. Stratification of individuals into body types provides a detailed picture of aging body shapes.

Table 2 List of body types and associated characteristics of body shape. Full size table

The incidence of body types is a function of age

The mean age of the body types ranges from about 45 to more than 65 years (Fig. 3a and Supplementary Fig. 6), reflecting a systematic change of the age distribution of the respective participants. The incidence of most of the body types markedly alters with age and locally deviates from the mean incidence, especially for younger and older people (Fig. 4a). Age-dependent changes are more pronounced for women than for men as indicated by the steeper slope of the respective curves in Fig. 4a. It corresponds to the stronger correlation of most of the meta-measures with age observed for women (Fig. 2b). Net changes of the relative frequency of body types are all together roughly twice as much in women (±94%) as in men (±43%; Fig. 4a, right part). Changes of the incidences of F-typess are observed in the complete age range, while the incidence of most M-types remains virtually constant above 60 years.

Fig. 4: The distribution of body types reveals a systematic shift from young age to older age body types. a Percentage distribution of participants per body types as a function of age (middle part). The sidebars show the respective percentages of individuals in each of the body types averaged over all ages (left side) and their changes between the latest and earliest age interval (right side), respectively. b Frequency distribution of age of the participants collected in the individual body types. Full size image

The body types B1, F1, and M1 show the highest incidence for middle-aged people of about 40–50 years, while their incidences then markedly decrease for elderly people, who enrich in F6 and M7. The incidence of F2, M2, and M3 is virtually independent of age. These body types collect participants from intermediate age ranges, which suggest compensation of in- and out-fluxes of type members upon aging.

Taken together, we find gender-specific aging of body shape where alterations of women are more pronounced than shape changes of men. Aging is characterized by the redistributions of body shapes towards specific body types of elderly people showing a narrower age distribution than body types of younger people (Fig. 4b).

Transitions between the body types suggest Life Course trajectories

So far, age-dependent alterations are described by changes of the mean meta-measures (Supplementary Fig. 6) and by the changing incidences of the body types (Fig. 4a). Both effects are linked because alterations of the meta-measures potentially change the incidences of the body types due to the re-classification of individuals between them. We applied a probabilistic approach to estimate such transitions. They are assumed to refer to pairs of individuals from two different body types with similar body shapes and they are obtained by counting all such similarity links between all pairwise combinations of body types (see heatmaps in Fig. 5a, b).

Fig. 5: Similarity links suggest an age course of body types. Frequencies of similarity links between female (a) and male (b) body types are shown as heatmaps. These link frequencies were used to construct a schematic overview of transitions between the body types in an age-versus-BMI coordinate system. It suggests a partly linear sequence of female body types (c), and a more compact structure for male ones with more mutual transitions between the different body types (d). Intersecting areas and arrow widths approximately scale with the number of corresponding links (see also Supplementary Figs. 6 and 7 for more details). The figures schematically illustrate the mean BMI and mean age of the body types in an arbitrary scale. Full size image

We found such links especially between “younger” body types (B1, M1, and M2 for men, and B1, F1, and F2 for women). Their number strongly decreases with increasing age (Supplementary text). Body types of the intermediate age range (M3–M5 and F3) form “transition” types linking “younger” with the “older” body types. The links typically refer to a relative shortening and broadening of the upper body (decreasing meta-measure H, increasing meta-measures B, K, and L; see Supplementary text). For example, the intermediate position of F3 suggests transitions from F1 and F2 towards F3 and from F3 towards F5 and F6 (see Fig. 5c). For men, links reflect a less pronounced age structure (Fig. 5d) in correspondence with the weaker age-dependent changes of M-types (Fig. 4a). Interestingly, F4 (women with massive bodies and thick girts) forms a relatively isolated body type virtually without similarity links to other body types. Younger women of the androgynous body type B1 link to F1, and younger men of B1 link to M1, whereby all of them collect slim bodies. The second androgynous body type B2 (big upper body) links to M4–M6, which all show larger upper body dimensions. In summary, similarity relations between individuals of different body types enabled us to identify possible transitions between the body types upon aging. They can be summarized into two major Life Course trajectories for women linking the younger and older body types F1 and F5, respectively, either by direct transitions or via the obese type F3, both affecting predominantly the dimensions of the upper body. For men, possible trajectories are more diverse, involve more inter-linked body types, and affect different parts of the body. Also for men one of this pattern of links reflects two major Life Courses, one via the obese type M5 and the other via the tall types M2 and M6.

Body types diversify the aging curves of anthropometric indices

We found that most body types develop specifically upon aging. For their better characterization, we decomposed the age dependencies of the “classical body indices” separately for each body type (Fig. 6). The body type-specific curves of body height roughly follow the course of the mean body height averaged over all participants (thick curve) with a slight scatter between them reflecting different body height levels. In contrast, the body weight and especially BMI curves of the individual body types show much stronger scattering (Fig. 6b, c).

Fig. 6: Body height, weight, BMI, and WTH of body types as a function of age. Curves were smoothed for each body type. Thick black lines indicate the mean parameter development averaged over all female (left panels) and male participants (right panels), respectively. Gender-unspecific body types B1 and B2 are not shown here due to low sample sizes. The background colors in c, d indicate different weight categories as indicated. The horizontal dashed line refers to minimum BMI-associated all-cause mortality (BMI = 24 kg/m2) and the dotted lines to hazard ratios of 1.5 taken from ref. 25. Full size image

Importantly, the BMI of the body types remains virtually constant, while the overall mean BMI increases until the age of 60–65 years. In other words, body typing roughly stratifies the population into virtually age-independent BMI levels, especially for women in the order F1 < F2 < F5 < F6 < F3 < F4 and, to a less degree for men M1 < M2 < (M3 ≈ M6 ≈ M7) < M4 < M5. M3, M6, and M7 are characterized by similar BMI levels (and body height), but different WTH levels. The relative small scatter between the body height curves of the individual body types indicates that body height is only a relatively weak determinant of body typing, while the much larger spread of the weight curves reflects its larger impact on BMI.

The WTH index is steadily increasing with age in most body types, reflecting a general apple-to-pear-like shift of body shapes, where the slope is largest for F-types with smallest WTH (F1, F2). WTH seems less suited as an age-independent marker index of body shape. The slope of the different WTH curves decreases with increasing WTH level, especially for women, leading to convergence of WTH indices and thus of stable pear-like body shape for elderly people. F6, accumulating elderly women, shows virtually constant WTH over age, and M5, accumulating obese men, is even slightly decreasing for participants older than 60 years. Interestingly, the female body type with the highest BMI, F3, does not show the largest WTH values, presumably reflecting a different fat distribution. Also, other body types of both sexes show differing relative BMI and WTH levels.

The mean BMI levels of F2 and M1 roughly correspond to a BMI value of about 24 kg/m2, which associates with minimum all-cause mortality25. The more obese types F4, M4, and especially F3 and M5, seem to associate with an increased risk based on previous data linking mortality risk and BMI25. Overall, stratification of body shapes into distinct body types levels out age-related alterations of body indices and enables the study of health-related associations in terms of defined anthropometric groups.

Association between body types, physical activity, and selected health and lifestyle factors

Next, we studied the physical activity of the participants of the LIFE study as a function of age and its association to the body types. The number of steps per day and the metabolic equivalent (MET) as measures of physical activity systematically decrease with age similarly for women and men (Fig. 7a). Among the body types, we identified more (F1, M1) and less (F3, F4, M5) active ones using age-matched reference groups for comparison (p value <0.001, Wilcoxon’s rank-sum test, Fig. 7b). The mean MET value of the body types decreases as a function of age, except for the most obese type F4 (Fig. 7c). The MET levels anti-correlate with BMI and weight values (compare with Fig. 6, r = −0.87). The plots of the mean BMI and MET values per body type as a function of their mean age can be roughly described by lines of opposite slopes (Fig. 7d), but obese body types (F3, F4, M5 and to a less degree, M3, M4) deviate from these lines towards low MET, while B2F has a slightly elevated MET value. Note that MET is normalized per kg of body weight. Consequently, the treated energy grows not in parallel to body weight of the participants. Low MET values were found particularly for F3, F4, and also M5, which were risk groups in terms of high BMI (see above).

Fig. 7: Physical activity of body types. a Physical activity as measured in units of the number of steps per day and MET decreases with age. b Body types divide into more and less active ones, where the former category collects younger and less obese individuals. Dashed lines indicate median values of the reference age groups, “+” and “−” symbols in the head line indicate significant differences between the body types and their reference groups with p values of <0.1 (+/−), <0.01 (++/–) and <0.001 (+++/−−−), respectively. c MET of the body types as a function of age resemble the respective BMI curves in Fig. 6 and reflects that high BMI associates with low physical activity. d The plot of body types’ mean BMI as a function of their mean age can be roughly described by lines of similar positive slopes for women and men (≈0.25 kg/m2 per year) if one excludes the obese types F3, F4, M5, and M4. MET provides negative slopes with larger variability of the values of the F-types and F4 as outlier showing lowest MET value. Full size image

We use the history of myocardial infarction (i.e., the prevalence of myocardial infarction in the previous life of participants, PMI) as one proxy to estimate the health risk of the body types. PMI of M-types markedly exceeds PMI in nearly all F-types, except for B2F (Fig. 8a). PMI steeply increases with the mean age for men’s types, but to a markedly less degree for women (Fig. 8b). We find slightly increased PMI for obese risk types of men (M5), while PMI is maximal for M7, presumably because of the increased mean age of this type (66.7 years). Age is obviously a relevant risk factor for elderly men compared to BMI and physical activity. Among women, the androgynous-type B2F shows strikingly high PMI. Notably, PMI is virtually independent of BMI and MET for women of all body types, except for B2F, while it increases/decreases with BMI/MET for men’s body types. Surprisingly, no case of previous myocardial infarction is among F4 collecting obese and elderly women (p = 0.11). Also, F3, another obese body type, associates with a relatively small PMI level. On the other hand, F3 and F4 collect, on the average, younger women than F5 and F6, suggesting that age constitutes the more relevant risk factor of PMI for women in contrast to men, who are under increased risk with increasing BMI for most body types.

Fig. 8: Myocardial infarction prevalence, lifestyle factors, and medication in body types. a Prevalence of myocardial infarction is much smaller for female (1.1%) compared with male (4.1%) participants of the LIFE study where however women of the B2F type have a strikingly high PMI value (7.4%). b Plots of PMI as a function of age, BMI, and MET consequently reveal much steeper slopes for M-types than for F-types. Women of the androgynous body type B2F are disproportionately affected by myocardial infarction. c Medication frequency of the individuals of the body types (within 7 days before their examination in LIFE) with drugs of the ATC groups C (cardiovascular system), G (genito-urinary system and sex hormones), and H (systemic hormonal preparations, excluding sex hormones and insulins), which all show anomalies for B2F. d Violin plots of the lifestyle factors alcohol consumption and smoking stratified by the body types. Alcohol consumption is higher for men than for women, and it slightly decreases with the mean age of the body types. Smoking among B-type women is more intense than among the other F-types and resembles that of men. Note that the violin plots reflect a bi-modal distribution for most of body types referring to non-smokers and smokers, respectively (“smokers” here subsumes current and former smoking; see percentage of smokers in the body type as indicated in the header). Full size image

The high PMI of the female B2F group is noteworthy, and it even exceeds the PMI levels of men’s body types (except M7). Androgynous women are obviously under elevated risk for myocardial infarction. To better understand this anomaly, we included alcohol consumption and smoking status as lifestyle factors, and also medication data available for the LIFE participants into our analysis. Particularly, medication of the group “C: cardiovascular system” according to ATC (Anatomical Therapeutic Chemical) Classification shows similar patterns as PMI, for example, higher percentage of medication in B2F and M7 (Fig. 8c). Obese and elderly women of body types F4–F6 take more medication than men of all BMI categories, except for oldest (M7) men. B2F women, on the other hand, take virtually no drugs of the medication categories “G: genito-urinary system and sex hormones” and “H: Systemic hormonal preparations, excluding sex hormones and insulins,” which considerably deviates from women of the other F-types. Women consume, on average, less alcohol than men, and the consumption decreases for body types of elderly women, but without marked specifics for B2F individuals (Fig. 8d). In contrast, B2F women show highest smoking level among women, which is comparable with that of men: 56% in B2F compared with 40% for all women and 59% for all men.

In summary, the physical activity of participants measured in units of MET anti-correlates with BMI and decays with age. Prevalence of myocardial infarction increases with age and/or BMI among men, but it is low among women, except those of the androgynous body type B2F, which, in turn, associates with high medication of group C drugs and relative extensive smoking.