Frequently Asked Questions
Questions and answers regarding Women
Q: Can I take something to alleviate premenstrual symptoms?
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Q: Do oral contraceptives affect a woman's metabolism?
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Q: What supplement or food changes are recommended for pregnant or expecting women?
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Q: Will my breasts shrink if I lift weights?
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Q: As a female, does orgasm affect my health?
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Q: Will my breasts shrink with weight loss?
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Q: Will doing chest exercises make my breasts look "perkier?"
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Q: I am a female. Will lifting heavy weights make me bulky?
A: While lifting weights will increase muscle, the rate is slow enough and androgens limited enough to not make you appear too 'bulky'.
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This page is catered to elucidating metabolic differences between men and women (specifically concerning what affects women, or what does not differ) and may address some issues that are exclusively feminine in nature such as exercise and pregnancy.
Anatomical and sexual differences will not be discussed unless needed.
Women v. Men: What is used for energy
Differences in Carbohydrate metabolism
Women are inable to carbohydrate load as effectively as men and do not experience significant increases in muscle glycogen content until they surpass 8g/kg carbohydrate/bodyweight.
Differences in Fat metabolism
During fasted exercise, women tend to burn a greater proportion of their energy as fats with no differences between the genders in regards to intra-muscular fat stores.
Differences in Protein metabolism
Women seem to oxidize less amino acids and protein during fasted endurance exercise relative to men.
Differences in Exercise metabolism
When carbohydrates are ingested during sub-maximal exercise (67% VO2 max), the bodies expected response of using more glucose for energy in lieu of fatty acids does not differ significantly between the genders, although a trend is shown for females to use more ingested carbohydrate as fuel rather than stored carbohydrate (glycogen) relative to males.
Along the lines of lower carbohydrate utilization, females tend to also have a reduced Respiratory Exchange Ratio (RER), indicative of less carbohydrate utilization. A trend of carbohydrate preservation in the face of metabolic stress exists in females.
In the fasted state, women also tend to burn more fat as a percentage during endurance exercise although overall calories do not differ.
Differences in hormones
Differences in Estrogen and Testosterone (steroids)
Women have a higher estrogen to testosterone ratio than men.
This higher ratio may be a reason why more fatty acids are used for energy rather than carbohydrates or amino acids at rest and exercise. This is an effect of estrogen per se, and occurs in men supplemented with estrogen as well. In experiments with rats, a trend of estrogen inducing preferential fat loss over glycogen usage is evident.
Along the lines of the aforementioned preservation of carbohydrate in the face of metabolic stress, these reactions may also be mediated by estrogen. Experimental models of animals show females having a higher survival rate during experimentally induced diabetes and a line of genetic knockout mice (mice lacking PPARa genes) had complete death of males by hypoglycemia, and only 25% females death; some males survived with estrogen administration. Estrogen may theoretically be useful in protecting from nonketotic hypoglycemia and rhabdomyolysis, but may inadvertently reduce overall carbohydrate usage for fuel and subsequent performance capabilities.
Differences in other hormones
Women appear to have less catecholamine (adrenaline, noradrenaline) release in respond to submaximal exercise, although the difference between genders is eliminated at higher intensities.