Getting lean requires serious commitment and single-mindedness over a long period of time. You have to train hard on a regular basis, eat carefully, and get consistent sleep. Of course, there are varying levels of leanness -- physique competitors might aim to achieve 10 to 14 percent body fat; whereas athletes or very determined individuals might aim for 15 to 20 percent body fat, depending on their aesthetic and performance goals. The process for achieving those levels, however, is the same; the difference is simply in the amount of time and compliance to your plan.
Nothing Without Nutrition
If you really want to be lean, you have to eat like it's your job. In order to support your training, while also reducing overall body fat, here's what you could expect to eat every day on your quest to become lean: protein such as lean meat, fish, poultry, eggs or protein powder at every meal, with a serving size roughly equivalent to your fist, with one more serving after your workout. One or two servings of carbohydrates like starchy vegetables, fruits or whole grains the size of your cupped palm per day. Two servings of fat per day, such as nuts, seeds, oils and nut butter the size of your thumb. Then fill up on vegetables, and three to five liters of water each day. That's it. No junk, no "treats," no alcohol.
Train Like a Machine
Becoming lean is a much easier process if you build your workout program around weightlifting and high-intensity interval training, or HIIT. Weightlifting is very effective for fat loss, and won't make you "bulky." It will give you noticeable muscle definition and tone, but most women don't have the hormonal capacity to become bulky. HIIT will also help you burn fat quickly. Four weightlifting sessions and two to three HIIT sessions, such as sprinting, each week should be the basis of your training schedule, along with slow forms of cardio like leisurely walking or swimming two to three times per week.
Sleep Like the Dead
Sleep is vitally important for getting lean. The Harvard School of Public Health recently published findings that lack of sleep is directly related to increases in body fat, and retention of body fat. Aim for eight to nine hours a night -- not only will you be training very hard and tiring your body out, but you will also be eating relatively low amounts of calories each day, which means your body needs longer to recover in order to keep meeting the demands you place on it.
Be Bloody Minded
The only way you will get lean is to be absolutely resolute about it. No one gets lean by accident. Being lean has to become your lifestyle -- you can't work at it for a couple of months and expect it to stick. This means sticking to your meal plans even when you'd rather go out for a social dinner, training when you've had a frantically busy day and you just want to go home, and going to sleep when it would be more fun to stay out with friends. It's hard. And it requires significant sacrifice. But that's how women get lean.