I disagree entirely with the idea that if a women works out heaps she's going to get gross guy muscles; it is physically impossible for the average female to get the bulky muscles of a guy without protein shakes and/or steroid use. Most women are not doing any where near enough exercise; many female martial artists in China - skinny and feminine - are exercising 7 hours day, at least 5 days a week. Exercise speeds up metabolism so you have to have be more mentally tough to ignore the increased hunger pangs.
Sodium and potassium are necessary for the function of many body organs, like the heart. So even though it makes you retain water (which sucks), it's necessary. Adding a pinch to water will allow your body to absorb the water more quickly (helping to flush out your body + rehydrate more efficient) without causing too much retention.
Your body turns fat (lipids), carbohydrates (simple sugars and complex carbohydrates) and protein into energy. Its preference is for carbohydrates, specifically glucose, to allow cells to metabolise. Glucose is necessary for cell function. The next option is fat (making ketones, which it can do but takes more energy to do, and the last option is protein - yes, your body will eat away at itself if starved for long enough. This includes heart muscle. Bad. Fat is necessary to make many substances in your body, such as hormones.
However, your blood glucose level is held tightly regulated by the hormones insulin and glucagon. Insulin stores glucose into glycogen and stores free fatty acids as triglycerides whilst glucagon breaks down glycogen and causes the building of new glucose from fat, or failing that, amino acids, as well as breaking down triglycerides into free fatty acids (which can then be made into new glucose).
Stored fat is for protection against cold, against physical trauma, and as a storage for glucose. So that's why you get "fat" skinny people who, after chronically starving themselves, store fat, instead of lean muscle.
Insulin = storage, glucagon = burning. So we want glucagon.
High glucose causes a lot of damage in the body for various reasons, and so insulin rises after a meal to lower it.
Contrary to popular belief, low blood sugar does not make you hungry, there are other hormones and chemicals involved in that.
The difference between simple carbs and complex carbs refers to the chemical composition and more or less, the amount of bonds in the chemical. The more bonds, the harder it is to break, so the longer it takes to convert to glucose. This is what the glycaemic index refers to. A longer time/energy means there is a smaller spike in glucose levels, so extra insulin and other hormones are not produced, making complex carbohydrates the best option for any carbs.
Your metabolic rate is the measurement of the rate at which your body metabolises, or burns, energy.
Eating protein and weight training will increase this energy. Avoiding carbohydrates (especially simple carbohydrates) avoids increases in blood sugar levels leading to the production of insulin and thus storing as fat. You do need a little as some tissues in the body can only run for the long term on glucose. Eat a little fat instead of carbohydrates, as fats are necessary, and because a low blood sugar leads to the release of glucagon, which leads to the burning of stored fat. There are different types of fat and depending on the type some are also good for your arteries and maintaining your blood pressure and cardiovascular health.
To simplify these types, saturated fat is bad; unsaturated fat is good. Monounsaturated fat is ok but polyunsaturated fat is goodgoodgood and found in sunflower oil and fish oil.
Fibre in the gut is good for encouraging healthy bowels. Fruit and vegetables are good for fibre and vitamins, although unfortunately they tend to have high glycaemic indexes/be full of simple carbs.
So in summary, for weight loss, avoid carbs, take a fibre supplement, perhaps a multivitamin, include "good" fats, lift weights and eat protein.
Edit - essentially muscles, being denser, have a higher need to metabolise to keep working.
When you anaerobically exercise, your heart works harder and your blood flow changes and you use up first the glucose in your system, then the glycogen (which last 10 - 18 hours ish on a fast) and then starts converting fats. So when you go running, etc, you are using up your stores of sugar, then fat to maintain a sufficient blood glucose level whilst supplying the increased demand to various organs. After you stop, it takes a while for your metabolism to slow back down as your organs take longer to return to the pre-exercise level.This is why it can be difficult to sleep with weight loss drugs, caffeine or exercise at night (although there are other bits involved).
Weight lifting is mechanical stress which encourages muscle development. This may mean the development of new muscle cells or the strengthening of existing muscles - depending on age, other factors, etc. With new muscle cells, your bodies resting metabolic rate is increased as they require more energy to run at a baseline level. If you run with more muscle, your metabolic rate will be increased than running with less muscle.
There are various different types of muscle fibres, which people have a natural predisposition to one type or the other, although people have both and with training you can purposefully increase the amount of one relative to the other. This is what slow twitch vs fast twitch or endurance vs sprint, etc refers to.
Women are designed to survive whereas men are designed to die first to protect the species. So we store fat better and have better peripheral vision whilst they get to be physically stronger.
Also girls, I urge you all to check your vitamin d and calcium to check your bone density. To have enough calcium you need to have 4 servings a day of calcium rich foods. A serving is 1 glass of milk, 1 tub of yoghurt, 1 piece of cheese, 4 cups of broccoli, 8 cups of spinach or some (I think 1.5 or more?) cups of kale... and I know a lot of you vegans may not be eating 32 cups of spinach in a day!
Good exercises for your bones (if you are young i.e. under 50 ish!) are ones where you hit something hard enough to jolt the bones, which gives them stress to make sure they improve and maintain density. Examples are running, skipping, maybe even dancing.
The initial bulky look when you first start exercising is usually just due to the increased muscle on top of the pre-existing fat, keep at it and the fat will be used up until you are left with the muscle. I would advise weight training being the primary focus for the first 3 months, and then rotate to primarily aerobic training for a week or so after, then begin to integrate the two.