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After puberty, can certain diets, exercise, and/or possible drugs affect masculine/feminine dimorphism in adults? We know dimorphism and/or morphology is a product of genes, but to what extent can this be altered through environment? Like, can chewing more give a more masculine jaw shape/angle? Can talking a certain way make a more deep, manlier voice? Can squinting give hunter eyes?

For women, can eating soy-based products increase hip-to-waist ratio? Estradiol? Feminization of the face, cheeks and etc.? Likewise, in males, can vigorous exercise, drugs/diet and etc. masculinize?

Sexual dimorphism I mean as in how they look and what makes assure genetic/reproductive value.

Aside from genes, basically, what extent can diet, foods, exercise and etc. affect epigenetics, morphology and sexual dimorphism in animals, namely humans? Any evidence/studies/work on this?

This isn't intended to be a medical/personal question thing -- more so, broad on any means a human and/or animal may use their environment to try and improve dimorphism and morphology/phenotype.

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There is a slight inaccuracy in your title question. Let's clarify to begin with:

I think you are asking whether environmental factors can affect sexually dimorphic traits. I don't think you are aiming to ask about dimorphism itself (i.e. the presence of apparent differences between the sexes) specifically. You're not interested in whether, say, food will affect sex dimorphism in humans but rather whether it can affect phenotypes which are sex-specific. It's a good correction to start with.

Can diet affect sexual dimorphism?

Of course. This is the case with all sexually dimorphic animals. A good example is nutritional deficiency, sub-optimal calorie intake or ingesting hormones or metabolically-active natural products from food. For instance, a male stag's antlers will not grow very much if the stag does not ingest enough phosphorus or calcium. This has drastic effects on its ability to reproduce, as often antlers are a key element in sexual selection in deer species.

Also, in some nutrient deficiencies, the body's ability to produce sex hormones is affected, which in turn affects secondary sexual characteristics such as jaw shape and the storage of fat. In bulimia and anorexia, periods become irregular due to the body's state of chronic starvation and inability to regulate menstruation with hormone cycles. Thirdly, diet can affect the ethology of disease (diabetes is a good example) which can indirectly affect sexual characteristics. There are many complex examples in which disease has an endocrinological (hormonal) component.

In addition, regular exercise, for instance, is well-demonstrated to affect testosterone levels.

It's important to keep in mind that not all traits which are sexually dimorphic are visible. For instance, smoking has an effect on sperm count, which is something not visible but still constitutes a sex-specific phenotype.

Can supplementation and drug-use affect sexual dimorphism?

Of course. I think taking steroids and hormones is an obvious example. I don't think this one needs explaining - a search engine can help here.

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  • $\begingroup$ > Of course. I think taking steroids and hormones is an obvious example. < But I've seen people -- guys in particular -- who've used steroids and it didn't seem to affect dimorphism of the face. It builds more muscle, but doesn't necessarily create masculine dimorphism face-wise (i.e., stronger jaw; wider face; larger warrior skull; powerful brow ridge and etc.). If this was true then virtually every guy who's used steroids would look/have some kind of highly masculine, dimorphic, cro magnon-esque face, which we know doesn't happen to most male steroid users at least (but female maybe). $\endgroup$ – Frederick Benson Dec 20 '18 at 23:34
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    $\begingroup$ I don't think facial features are as 'plastic' in adulthood. Once they are set up, they change relatively little in shape compared to musculature, i.e. overall skeletal shape can't be changed much. The obvious changes that steroids induce are not skeletal, they are most obviously related to connective tissue, muscle, skin, fat storage, etc. Also, transgender individuals who have 'transitioned completely' with the help of sex hormones tend to have distinct facial features that are not typical of their biological sex. You can certainly masculinize or feminize faces artificially with hormones. $\endgroup$ – S Pr Dec 21 '18 at 11:25
  • $\begingroup$ Then wouldn't your point be rendered invalid then? If you're a man with bad, non-dimorphic male bone structure and hormones do not make a difference in this way, how would they affect dimorphism then? A non-dimorphic face is bound by bones primarily. How would fat/skin/etc. matter if the overall structure of the hard tissue is what appears non-masculine? In fact you agree yourself with the "distinct facial features that are not typical of their biological sex" part you mentioned. It seems hormone manipulation post-puberty barely affects dimorphism. $\endgroup$ – Frederick Benson Jan 16 at 4:40
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    $\begingroup$ You're using the word dimorphic incorrectly. I wouldn't use terms like bad either, it's not clear what you mean. I don't think you appreciate the diversity of things taking place when you introduce steroids. If a man takes estrogen, he will grow soft tissues on his breast region. Breasts are not typical male characteristics. If a woman takes testosterone, she will find an increase in muscle mass, changes in fat storage and a deeper voice. Muscle tone or body shape are very typical indicators of sex-specific traits. Your last statement that hormones barely affect dimorphism is thus incorrect. $\endgroup$ – S Pr Jan 16 at 13:39
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Can diet, supplements, drugs or exercise improve masculine appearance in men and feminine appearance in women?

In short, some of the mentioned factors can affect the appearance of the muscles and fat tissue but not the bones, face or genital organs. I'm not discussing about hormonal treatment here.

MUSCLES

Resistant exercise in combination with sufficient calorie and protein intake can significantly increase the muscle mass (Essays in Biochemistry, 2008) in the limbs, torso and neck. You can't realistically expect that chewing or other facial exercises will significantly change the shape of your facial muscles.

FAT

If overweight, a hypocaloric diet can make you lose body fat and thus:

  • make you look more fit
  • make your jaw angle more prominent
  • reduce your breast fat (gynecomastia)
  • decrease your waist-hip ratio

A diet can result in increase or decrease, but not redistribution, of body fat, which is genetically determined (Diabetologia, 2014).

BONES

There seems to be no natural and healthy way by which you could increase the thickness or length of your bones or change their shape in adulthood.

Bone thickness

Exercise does not significantly increase the thickness of your bones - only 1-2 mm increase was observed in one study in tennis players (American Journal of Sports Medicine, 1994).

High intake of calcium, vitamin D, other nutrients or supplements in adulthood also does not likely visibly increase the diameter of your bones (it may increase bone cortical thickness or bone density, though).

Bone length

I haven't found any studies that would show how exercise or diet could increase bone length or shape in adults.

Jawline

The shape of jawline is mainly determined by the shape of the jaw bone. While the jaw angle can be affected by the genetically determined thickness of the chewing muscles (Scientific Reports, 2018), it does not sound realistic to change the jaw angle by chewing or other exercise.

Shoulder and hip wideness

The shoulder and hip wideness is genetically determined by the length and width of the bones in the shoulder and pelvic girdle and cannot be significantly increased by exercise or diet.

GENITALIA

I'm not aware of any exercise, diet or supplements that would significantly change the shape of genital organs.

VOICE

There are psychological factors, attitudes, conscious effort and exercises that can significantly affect someones voice.


Hormones found in food

Soy and some other foods are high in phytoestrogens that can have some pro-estrogen activity, but do not likely significantly affect the appearance of the muscles or bones.

Nevertheless, the only positive effects of phytoestrogens on bone observed so far in post-menopausal women have been small and limited to the lumbar vertebrae. (Baillière's Clinical Endocrinology and Metabolism, 1998)

Estrogen or soy isoflavones given to postmenopausal women results in a small increase in lean tissue mass. (Appl Physiol Nutr Metab. 2008)

Hormonal drugs

Estrogen, testosterone, corticosteroids and other steroids and growth hormone can affectsome of the following features: the morphology of genitalia, muscle mass, body fat distribution, facial appearance and voice.

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